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General Category => Tech Corner => Topic started by: spacetiger on June 11, 2017, 01:09:48 AM



Title: CB-1 oem rear shock
Post by: spacetiger on June 11, 2017, 01:09:48 AM
I see some are working a possible rear shock solution.  I thought I'd help a bit by posting a few observations from looking into the oem shock.

I disassembled the shock and took some key measurements:
 - free length of the spring: 7.048"
 - installed length of the spring:  6.449"
 - total stroke of the shock:  1.53"  (corrected)
 - estimated stroke to the rubber stopper:  0.866"
Note:  the preload of the bike was never set right/weight of the rider was great = pulverized the rubber stopper as there wasn't one on the shock.

Pic 1:  shock components:

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%201_zpspijrzm9k.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%201_zpspijrzm9k.jpg.html)

Pic 2:  Testing the spring, here it is ~ "fully" compressed (1.4385"):

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%202_zpsu8lvzirj.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%202_zpsu8lvzirj.jpg.html)

Pic 3:  Gathering the data points and plotting them (using excel), you can see the spring is a 2 rate spring (red lower and blue upper) by looking at the upper curves.  The red line is the lower rate = 1/0.001084 = 923 lbs/in.  The upper rate = 1/0.000807 = 1,239 lbs/in.  Of more importance is finding the crossover point.  That happens when the equation of the 2 curves are equal to each other.  You solve for the load at that crossover point, then solve for spring length when that happens.  That length is equal to the total of the gaps between the tightly wound coils.  

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%203_zps1rae0xmq.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%203_zps1rae0xmq.jpg.html)

Pic 4. With this information, you can determine the capacity of the spring as it is installed (the preload selector is on the 1st preload indent).  The installation preload of the spring is (7.048" - 6.449") = 0.599".  With 0.599" of initial preload compression, the installed crossover point is now at Y = (1.059 - .599) = 0.46".  Using the calculated rates, preload distance and cross over, you can show the as designed spring capacity (see lower red/blue curves).  It shows the spring doesn't start to compress until there is at least 552 lbs of force.  Then the spring compresses at 923 lbs/in until the spring has compressed 0.46" (all the small tight coils on the spring have compressed) and the spring transitions to the higher rate (1,239 lbs/in) and will continue to compress to a total distance of 0.866".  At that point, the shock would be compressed enough to reach the rubber stopper (if it was still there).  If the shock continued to compress, the spring capacity at total compression is 2,185 lbs.  

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%204_zpscduduin0.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%204_zpscduduin0.jpg.html)

There is more work to fully understand the rear suspension.  I need to measure the shock relationship to swingarm movement + I need to measure the damping setup of the shock.  I will not be able to do the later until the shock dyno is fully set up (maybe a few months away as I have to fabricate end pieces that can hold the shock).  But, this should be of sme help as you are looking for other options.  I don't think a VTR shock will work as the spring is not as stout as the CB-1's.  I think if you just replace the spring with an aftermarket 7" length spring with the correct rate, that might be the cheapest solution.  

Jerry    


Title: Re: CB-1 oem rear shock
Post by: a_morti on June 11, 2017, 03:20:23 AM
Very cool thank  you.

It's a progressive spring. Since one end is would tighter, every time a coil binds the sprig effectively becomes shorter which inreases its spring rate. Clever way to give a progressive ride without linkages.


Title: Re: CB-1 oem rear shock
Post by: spacetiger on June 11, 2017, 08:10:22 AM
a_mori,

The spring isn't a progressive spring.  It is a 2 rate spring.  I tried a 1st order polynomial curve fit through the data.  It is close, but doesn't fit well at the upper range.  If it was a progressive rate spring, the polynomial fit would have yielded the best curve fit (R2).  Linear curve fitting the data at the bottom (red rings around the black dots) and the upper (blue rings around the black dots) yielded the best curve fits as indicated by the R2 numbers on the graph.

When you look at the spring (pic 1), you can see the 2 separate coil rate windings.  The top close spaced windings, compress together until they bind up.  If you measured the distance between these coils and added them up, you'd get 1.063".  That's when you transition to the higher rate spring that has the coils spaced much wider apart.  Its impressive that they could make this kind of spring in so short of length.  

I have seen these 2 rate springs on other Honda bikes.  The lower rate is for solo riding, and the higher rate when 2 up.  The problem is that the rates are for people who don't weigh very much.  For a heavier solo rider, you end up putting so much preload in to set the sag, you are almost out of the initial rate of the spring, so you are essentially riding on the upper rate of the spring.  If you had a straight rate 1,200 lb/in spring preloaded at the same ~0.6", you would have a capacity of (0.6 x 1,200) + (0.866 x 1,200) = 720 + 1,039 = 1,759 lbs (vs. 1,479 lbs).  That is 280 lb more capacity (~19% more capacity) than stock.  That spring spring swap (~$85) might be the only thing most riders need to do to make the shock workable for them; you would not have to revalve the shock as the new rate of the spring is close to the upper rate of the spring, so it should still work.  I even think you could use a 1,300 lb/in spring (for much heavier riders) to give you (780 + 1126)-(1479) 427 lbs more capacity (~29%) more capacity and still not have to change the valving.  I should also mention, the move to a straight rate spring will challenge you a bit when you are trying to measure bike and rider sag as they will be much smaller numbers than you are used to seeing.  I consider that to be okay as the upper end of the spring capacity is what you are looking to gain.

So, all you riders looking for a cheaper shock option, just change your spring to either a 7" x 1,200 or 1,300 lb/in spring.  Once I can get some other measurements done, I can tell you what rider weights should be using what rate spring.

Cheers from the math department,
Jerry



Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 11, 2017, 11:55:00 AM
very well calculated analysis "Spacetiger".
So...change "which" spring out? the spring out of the stock CB1 OEM rear shock to a 1200lb or 1300lb spring?

Is that what your findings are indicating? That all a heavier (and much older) rider needs to do is swap the stock OEM CB1 spring to a simple 1300lb spring? wow....that's and awesome cheap fix.

Watching this thread closely.

a_mori,

The spring isn't a progressive spring.  It is a 2 rate spring.  I tried a 1st order polynomial curve fit through the data.  It is close, but doesn't fit well at the upper range.  If it was a progressive rate spring, the polynomial fit would have yielded the best curve fit (R2).  Linear curve fitting the data at the bottom (red rings around the black dots) and the upper (blue rings around the black dots) yielded the best curve fits as indicated by the R2 numbers on the graph.

When you look at the spring (pic 1), you can see the 2 separate coil rate windings.  The top close spaced windings, compress together until they bind up.  If you measured the distance between these coils and added them up, you'd get 1.063".  That's when you transition to the higher rate spring that has the coils spaced much wider apart.  Its impressive that they could make this kind of spring in so short of length.  

I have seen these 2 rate springs on other Honda bikes.  The lower rate is for solo riding, and the higher rate when 2 up.  The problem is that the rates are for people who don't weigh very much.  For a heavier solo rider, you end up putting so much preload in to set the sag, you are almost out of the initial rate of the spring, so you are essentially riding on the upper rate of the spring.  If you had a straight rate 1,200 lb/in spring preloaded at the same ~0.6", you would have a capacity of (0.6 x 1,200) + (0.866 x 1,200) = 720 + 1,039 = 1,759 lbs (vs. 1,479 lbs).  That is 280 lb more capacity (~19% more capacity) than stock.  That spring spring swap (~$85) might be the only thing most riders need to do to make the shock workable for them; you would not have to revalve the shock as the new rate of the spring is close to the upper rate of the spring, so it should still work.  I even think you could use a 1,300 lb/in spring (for much heavier riders) to give you (780 + 1126)-(1479) 427 lbs more capacity (~29%) more capacity and still not have to change the valving.  I should also mention, the move to a straight rate spring will challenge you a bit when you are trying to measure bike and rider sag as they will be much smaller numbers than you are used to seeing.  I consider that to be okay as the upper end of the spring capacity is what you are looking to gain.

So, all you riders looking for a cheaper shock option, just change your spring to either a 7" x 1,200 or 1,300 lb/in spring.  Once I can get some other measurements done, I can tell you what rider weights should be using what rate spring.

Cheers from the math department,
Jerry




Title: Re: CB-1 oem rear shock
Post by: a_morti on June 11, 2017, 12:19:12 PM
a_mori,

Knowledge bomb


I am very impressed by this. Is this your job or how do you have access to this knowledge?


Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 11, 2017, 12:25:05 PM
Spacetiger:
which spring or where can you recommend purchasing a 7"x1300lb spring from?
Got any dealers? And how much would something like that cost?
thanks for your expertise.


Title: Re: CB-1 oem rear shock
Post by: a_morti on June 11, 2017, 01:40:04 PM
Penske certainly used to do that.


Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 11, 2017, 02:00:44 PM
awesome!...calling Penske first thing Monday.


Title: Re: CB-1 oem rear shock
Post by: spacetiger on June 11, 2017, 04:09:12 PM
Don't go buying stuff just yet.  Even though my time is limited, you guys can do some of the work. 

If you just want to stay with the stock shock and you are on a very limited budget, I can guide you on how to pick a new spring that will match your weight.  If 5+ riders will do the following and report back your numbers, I will be able to more precisely guide you in getting your spring rate correct.  But keep in mind, this does not include sorting out the damping.  You have to determine if the damping is still acceptable.

Here is what 5+ riders need to do.
1. You have to insert a nylon washer onto the shock shaft so you can collect shock displacement measurements.  To get the nylon washer on, you cut the washer and use a needle nose pliers to feed the washer through the spring and onto the shock shaft.  You might have to turn the washer sideways to slip it on the shaft.  You can get a washer for $1 at Lowes or Home Depot.  Make sure the ID of the nylon washer is snug enough to hug the shock shaft.  If you have to add some electrical tape around the washer to reduce the ID, that is okay. 
2. Put the bike on the centerstand
3. Dial out all the preload on the rear shock
4. Push the washer up to the shock body
5. Gently, let the bike off the centerstand, then put the bike on the centerstand again - do not get on the bike.  The weight of the bike will compress the shock and move the nylon washer.  Measure the distance the washer moved - try to be as accurate as possible, say within 1/16".  It is tight in there, but if you use a popsicle stick and pencil, you can mark the distance and measure the marks after you are out of the shock spring.  Then push the washer back up against the shock.  This distance I will call the bike sag.
6. Now you mount the bike and gently take the bike off the centerstand.  Balance yourself and lift your legs off the ground so your weight + the bikes is on the suspension.  Then, dismount and put the bike back on the centerstand.  Be careful not to bounce the bike.  With the bike on the centerstand, remeasure how far the washer moved.  This is what I will call rider sag.
7.  Go measure yourself as you were dressed so I have the exact rider weight for the rider sag test.

Thats it for now.  If 5 of you will do this and post the results it will give me enough spread in the reported data to develop an initial sag/spring strategy if that is all you plan to do.

Just so you know my plans; my long term plans is to build a showa Frankenstein shock.  That is, I will be using parts from 2-3 shocks + a racetech piston so I can build the shimstack for my street bike.  I figured it might run me about $350 to do this.  It will not be a lightweight shock, but it should have very good damping characteristics and will be well matched to the spring.  This project will have to come after the Can Am rear suspension project.  So, 3-4 months from now... :-(


Title: Re: CB-1 oem rear shock
Post by: spacetiger on June 11, 2017, 04:19:47 PM
a_mori,

Knowledge bomb


I am very impressed by this. Is this your job or how do you have access to this knowledge?

I'm just a rider like you.  I am an engineer my education and profession, so it shapes how you go about things.  Because some of my more recent bikes have much more stout springs, I have found the need to get better equipment to measure and verify things.  I justified it in my head as giving up one motorcycle so I can get all of my other motorcycle suspensions sorted out properly now and into the future.  I found precision information on the internet is lacking because most riders don't buy this kind of equipment because of the expense.  They tune by rules of thumb.  The guys that have access to good equipment, don't post because that is their livelihood, so why give it away free.  The technical aspects are not too difficult to sort out - if you have the right equipment.   I have a very good spring tester, accurate to 2%, so I can characterize spring rates.  I also recently acquired a shock dyno capable of driving shocks up to 5.5"/sec.  That is plenty good enough to verify/valid shim stack setups in shocks and forks.  Since I don't make my livelihood this way, I will freely share with my fellow riders.

Lets see how this goes.

Jerry


Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 11, 2017, 10:01:41 PM
Maybe that's why they call you the "SpaceCowboy"....err...."Spacetiger" that is. Isn't there a song about a spacecowboy?


Title: Re: CB-1 oem rear shock
Post by: spacetiger on June 11, 2017, 10:12:49 PM
You are thinking of rinestone cowboy


Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 11, 2017, 10:20:56 PM
No....I know rhinestone cowboy...

I'm thinkin' of song that goes something like..."Spacecowboy...gansta of love".
"...some people call me the Space Cowboy..yeah"...

https://www.youtube.com/watch?v=YZo88P1Ie94



Title: Re: CB-1 oem rear shock
Post by: ModerateFkr on June 12, 2017, 10:36:24 PM
No....I know rhinestone cowboy...

I'm thinkin' of song that goes something like..."Spacecowboy...gansta of love".
"...some people call me the Space Cowboy..yeah"...

https://www.youtube.com/watch?v=YZo88P1Ie94



I know the Steve Miller Band song very well from the late '70s VintageHunter. A local band used to cover it every Sunday night at the Blessington Carriage pub. Steve Morgan, Mike Jackson and Micky ? who used to play bass - with his head in the bass bin!!! Damn! I always could remember Micky's last name. Anyway, they were great.

And I'm beyond impressed by your work spacetiger. I'm an aircraft engineer by early training, but you took this thing to a new level. I love your approach to data gathering. I will endeavour to get some figures for you. Somewhere I have a good pair of inside callipers and a micrometer and dial gauge. I just need to find the right nylon washer. I'm busy building storage solutions a few miles from my bike for the next week or so, but as soon as that's complete, I'll be on the case.

Not sure who sells just springs in the UK though. Still also considering playing with a Blackbird shock if one turns up cheap.

I'm copy/pasting your work into a Pages document for further study. Great work bro.


Title: Re: CB-1 oem rear shock
Post by: spacetiger on June 12, 2017, 11:32:19 PM
most excellent ModerateFkr on the possibility of gathering some data.

The buy of the blackbird shock will not be a total loss as I have already bought one as they are pretty cheap.  I'll do a quick check of that spring tomorrow. The reason I bought mine is to possibly contribute to the Frankenstein Showa shock build.  I have not pulled mine apart, but I was betting on the lower (and long like the CB-1) spring perch can replace the CB-1's lower perch.  That swap allows me to get lowspeed rebound adjustability in a shock body that didn't have one.  I don't think the blackbird shock body is the best as it is not as wide as the CB-1's.  The CB-1 is right at 2" so it can accommodate a bigger RT piston.  That will give you more tuning options.  I'm searching other Showa body shocks for lowspeed compression adjustability options via a remote reservoir.

Back to length. I need a shock with a length 8mm longer than stock.  I have to do a little math on another computer as I'm limited during the work week on this computer.  You can lengthen the stock shock about 5mm (max).  If you are on a budget and staying with the stock shock, I'll post tomorrow how to do this.  If you do this, you will have to add a spacer to keep the 7" spring length under the correct amount of preload.

Jerry



Title: Re: CB-1 oem rear shock
Post by: a_morti on June 13, 2017, 05:28:27 AM
Cbr900 shocks have all the adjustability you can want and are a little longer than cb-1 shocks. The springs are way too soft ofc, but looks like you have the tech to work it out.

http://www.customfighters.com/forums/showthread.php?t=12827


Title: Re: CB-1 oem rear shock
Post by: ModerateFkr on June 13, 2017, 09:38:42 AM
Cheers Jerry,

I'm hoping Nicknitrous had some luck with his Blackbird swap. Looks like we're heading towards amassing some serious data on the rear suspension of the CB-1. Although I'm not planning to make a race machine, and to be fair, in my youth I managed several pretty fast laps of Donington on my beautiful, though weave prone old CB250G5, I'm now a fair bit heavier, and out of practice on two wheels. So I need a safe ride as much as anything. But if I can really tune it to my weight and riding style, especially with a frankenshock I've built myself, I'll be delighted. Plus ill have something else to yak about when I visit Matlock Bath, Brighton and the Ace Cafe ;))

I've got spring compressors that I bough recently to do the rear suspension on my Mondeo. What other special tools will I need to strip shocks?



Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 13, 2017, 10:51:00 AM
I keep reading this option as being a "no-brainer" but...I also read that this option doesn't allow the shock to be rebuilt?
Cbr900 shocks have all the adjustability you can want and are a little longer than cb-1 shocks. The springs are way too soft ofc, but looks like you have the tech to work it out.

http://www.customfighters.com/forums/showthread.php?t=12827


Title: Re: CB-1 oem rear shock
Post by: Sugs on June 13, 2017, 09:35:18 PM
I keep reading this option as being a "no-brainer" but...I also read that this option doesn't allow the shock to be rebuilt?

Pretty certain they can be rebuilt.  If you go to racetech.com and look for CBR900RR, it shows options for the rear shock, all years.  If it wasn't rebuildable there would be no options for the rear, like the Honda 919 for instance.


Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 13, 2017, 09:54:48 PM
Really? the Honda CBR900RR OEM rear shock "can" indeed be rebuilt?
huh. I wonder how much that'll set me back from RaceTech. I'll call them tomorrow and find out.


Title: Re: CB-1 oem rear shock
Post by: Sugs on June 14, 2017, 12:57:28 AM
1. You have to insert a nylon washer onto the shock shaft so you can collect shock displacement measurements.  To get the nylon washer on, you cut the washer and use a needle nose pliers to feed the washer through the spring and onto the shock shaft.  You might have to turn the washer sideways to slip it on the shaft.  You can get a washer for $1 at Lowes or Home Depot.  Make sure the ID of the nylon washer is snug enough to hug the shock shaft.  If you have to add some electrical tape around the washer to reduce the ID, that is okay. 
2. Put the bike on the centerstand
3. Dial out all the preload on the rear shock
4. Push the washer up to the shock body
5. Gently, let the bike off the centerstand, then put the bike on the centerstand again - do not get on the bike.  The weight of the bike will compress the shock and move the nylon washer.  Measure the distance the washer moved - try to be as accurate as possible, say within 1/16".  It is tight in there, but if you use a popsicle stick and pencil, you can mark the distance and measure the marks after you are out of the shock spring.  Then push the washer back up against the shock.  This distance I will call the bike sag.
6. Now you mount the bike and gently take the bike off the centerstand.  Balance yourself and lift your legs off the ground so your weight + the bikes is on the suspension.  Then, dismount and put the bike back on the centerstand.  Be careful not to bounce the bike.  With the bike on the centerstand, remeasure how far the washer moved.  This is what I will call rider sag.
7.  Go measure yourself as you were dressed so I have the exact rider weight for the rider sag test.

I can try to do this, but do you have a process to do it without a center stand as I don't have one on my bike?


Title: Re: CB-1 oem rear shock
Post by: spacetiger on June 14, 2017, 06:46:58 AM
sugs,

If you do not have a centerstand, you can use your sidestand.  Skip the part where you do the bike sag.  You'll have to rely on the data from others for the bike sag measurement.  Try to get the rider sag measurement.

I will try to post my results this weekend.  I did some work yesterday and realize how tight the shock is buried in the bike.  You will have to remove the shock from the bike to get the nylon washer on.

ModerateFkr:  we're of the same mindset on the end result.

Jerry


Title: Re: CB-1 oem rear shock
Post by: ModerateFkr on June 14, 2017, 08:14:36 AM
sugs,

If you do not have a centerstand, you can use your sidestand.  Skip the part where you do the bike sag.  You'll have to rely on the data from others for the bike sag measurement.  Try to get the rider sag measurement.

I will try to post my results this weekend.  I did some work yesterday and realize how tight the shock is buried in the bike.  You will have to remove the shock from the bike to get the nylon washer on.

ModerateFkr:  we're of the same mindset on the end result.i

Jerry


Hi Jerry,

Rolling the back wheel of the bike off the edge of a step or lump of wood or a concrete block the height of a pavement/sidewalk edge could have the same effect as rolling off the centre stand I suppose.  But access to the unit is a bugger! Long nosed pliars? Not had chance to review the job yet.

It's a logical mindset, and a sensible place for all bikers to start. If you happen to end up with a safer part time racing snake too, well that's a bonus IMHO.

Good luck in the lab. I'm moving and replumbing electrical appliances and building storage spaces for the next few days.



Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 14, 2017, 10:45:43 AM
my CB1 doesn't have the center stand as well.
Let me see what I can do this weekend. if you got photos of the whole "nylon washer" process that would surely help.
1. You have to insert a nylon washer onto the shock shaft so you can collect shock displacement measurements.  To get the nylon washer on, you cut the washer and use a needle nose pliers to feed the washer through the spring and onto the shock shaft.  You might have to turn the washer sideways to slip it on the shaft.  You can get a washer for $1 at Lowes or Home Depot.  Make sure the ID of the nylon washer is snug enough to hug the shock shaft.  If you have to add some electrical tape around the washer to reduce the ID, that is okay. 
2. Put the bike on the centerstand
3. Dial out all the preload on the rear shock
4. Push the washer up to the shock body
5. Gently, let the bike off the centerstand, then put the bike on the centerstand again - do not get on the bike.  The weight of the bike will compress the shock and move the nylon washer.  Measure the distance the washer moved - try to be as accurate as possible, say within 1/16".  It is tight in there, but if you use a popsicle stick and pencil, you can mark the distance and measure the marks after you are out of the shock spring.  Then push the washer back up against the shock.  This distance I will call the bike sag.
6. Now you mount the bike and gently take the bike off the centerstand.  Balance yourself and lift your legs off the ground so your weight + the bikes is on the suspension.  Then, dismount and put the bike back on the centerstand.  Be careful not to bounce the bike.  With the bike on the centerstand, remeasure how far the washer moved.  This is what I will call rider sag.
7.  Go measure yourself as you were dressed so I have the exact rider weight for the rider sag test.

I can try to do this, but do you have a process to do it without a center stand as I don't have one on my bike?


Title: Re: CB-1 oem rear shock
Post by: spacetiger on June 14, 2017, 06:59:57 PM
I probably should have posted a few more details of the journey this is going to be.  Right now, it is a bit early to jump to shock options.  I know that is the natural thing we ask, but we have to lay some ground work.  Hopefully this post will help some.

We have to make sure we understand the oem suspension geometry before we go making changes, so we can make informed changes no matter what kind of end state we want to achieve.  That way its not guesswork on the end result.  You should be able to get the end state 1st time out of the gate.  So, we need to understand the rear suspension geometry.  It will take 2 posts to do this.  I can post half of it tonight and with any luck, can get the 2nd half done tonight for a posting this weekend.  Then with some sag and riding data, we can complete the rear data set to allow some changes.

So, first step is to understand the oem shock to swing arm geometry.  In pic 1 you can see a theoretical suspension where the shock compresses a distance and the suspension moves the same amount.  that relationship is depicted by the red diagonal line.   The doted line shows an example of the shock compressing 2" and the swing arm compressing 2".  This nice linear relationship isn't likely to be found in the real world because the lower shock mount has to be at the rear axle and be almost oriented vertically (90 degrees).  The closest bike I have ever seen to this is the Honda PC800.  That bike has ~vertical rear shocks.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%205_zpsfpgyy967.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%205_zpsfpgyy967.jpg.html)

So now I have to collect this information.  Because the access is so tight, i have to add a "crude" ruler to the shock so I can eyeball how much the shock has compressed - see pic 2.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%206_zpskua1yfve.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%206_zpskua1yfve.jpg.html)

Then, I install the shock and set up the bike with a jack under the swing arm.  Here, I can eyeball the shock compression distance, then measure the change in axle height.  Here is the test configuration.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%207_zpshdeopwvy.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%207_zpshdeopwvy.jpg.html)

Once you collect 5 data points, it is enough to curve fit the shock to swing arm relationship.  In this pic it is a nice curve fit.  I extrapolate the curve out to where the spec rear suspension is stated (110 mm) and the measured max shock compression potential.  That dot is the brighter blue dot at about 1.5" shock compression/4.3" swing arm compression.  You can see the curve fit at that point is very close to the stated oem rear suspension travel/shock measurements confirming I have a good curve.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%208_zpszmurg0ri.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%208_zpszmurg0ri.jpg.html)

Just to show another shock/swing arm relationship, in this curve I had done on my HD XL1200T (green curve).  Every bike is different, so you have to do this everytime you are going to make suspension changes so you know what the possible outcome is likely to be.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%209_zpsqfh9b6ly.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%209_zpsqfh9b6ly.jpg.html)

Now I can understand the oem set up integrating the spring info with the shock/swing arm relationship.  In this curve, it would show what standard suspension guidelines would yield.  The red/blue line shows what spring rate you are using based on the shock compression distance.  The standard guidelines is to set rider sag at about 25% of suspension travel.  You do this by adjusting the preload for rider weight.  Once you set this, you can see you have a max of 1.24" of shock compression to go which translates to about 3.25" more of suspension travel to go.  That is for solo or 2 up riding.  The problem with this is that the capacity of the shock (spring/damping) isn't up to more beefier riders or the more aggressive rider.  You can also see the where the rubber stopper begins; the total reported suspension travel means you smash the stopper to pieces if your suspension strategy is to use most or the entire shock stroke.  This leads to the question, how and what to change to best set up the suspension for you instead of using a setup for a wide range of riders armed only with general rules of thumb(?).

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2010_zps9zr5srqp.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2010_zps9zr5srqp.jpg.html)

Math can help you figure out some options before you actually change things and is free.  To verify what is doable, safe and will make sure the center stand still works, we measure and check for options.  On the center stand, I see the oem setup leaves a distance of about 1.75" from tire bottom to ground.  If I am willing to live with 75% of that distance, then I want to look for an option of shock length that gives me (0.75 x 1.75") a 1.313" length.  I do a quick check of what is possible with the oem shock.  In this pic, I unwind the lower shock clevis until it is barely hanging on the shock shaft.  That max [unsafe] distance extension is ~11 mm.  It takes 5.5 full turns to screw on the clevis (5.5 x 360 degrees) = 1,980 degrees.  If I back off 20% so I stay in a safe extension, I find I can unwind ~400 degrees and yield a ~3 mm extension. edit:  the 2nd pic was the result of unwiding 2 full turns (720 degrees); that yielded over 5 mm of extension.  A nice gain, but perhaps not margin on the clevis to shock shaft overlap.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2013_zps8u7zhcdv.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2013_zps8u7zhcdv.jpg.html)

More math.  The equation of the curve fit can be used to show what happens if I lengthen the shock 3mm and 1.3".  I have integrated the max 4.3"/1.5" shock with the 5 data points to update the equation of the curve then project backwards.  Because of the oem geometry, i do not have to lengthen the shock very much to move the swing arm a much greater distance.  The small 3 mm (1.18") change moves the swing arm almost 0.5" (~0.47").  You only have to lengthen the shock by 0.32" to lower swing arm ~1.3".  So now, you know what length to make the Frankenstein shock (0.32" longer than stock).  Anything longer will put the rear tire on the ground.  BTW, the VTR1000 shock is 1.2" longer than the oem CB-1 shock - so it is too long.  If you use this shock, the rear wheel will not only be on the ground with the center stand, the spring will be compressed and make it easy to bump the bike off the center stand!  BTW, The CBR900 shock isn't long enough... I measured it already.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2011_zpsau6kplgm.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2011_zpsau6kplgm.jpg.html)

Assuming you can make the Frankenstein shock this long, you can start to plan the suspension strategy.  In this pic, it depicts a single rate spring on a longer shock with the same 1.5" max stroke.  You set the rider sag point at 20% and make it based on the shock stroke - not the suspension stroke.  The reason for this, the initial starting point has the best geometry for rake angle.  So you don't want to give away the best steering geometry just sitting on the bike.  You can also select the height of the rubber stopper so the nylon washer will always be able to tell you how much of the suspension you are using when you ride solo.  So knowing the range you want to stay in for good steering geometry, you can pick the spring rate and damper strategy for your solo riding weight.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2012_zps5439ytik.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2012_zps5439ytik.jpg.html)

So, you know more about the go forward plan.  I will measure suspension geometry (rake and trail) for different rear axle heights tonight (hopefully).  I'll try to finish that and post it this weekend.  After that, we need some empirical data on bike and rider sag + some riding data (to characterize the damping of the rear shock).  Once I get the shock dyno set up, we'll have better data - but, until then, we will only have what the riders can contribute via the nylon washer data.  I'll post this weekend how to do this.

Cheers,
Jerry  

Note:  a special thanks to all my teachers that helped me learn many things...


Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 14, 2017, 07:46:12 PM
one word........................."numb"


Title: Re: CB-1 oem rear shock
Post by: spacetiger on June 14, 2017, 09:10:38 PM
VH, numb nuts?  We're are not going to do this half ass you know.

Anyways, some pics to break up the math/graphs.

Pic 1.  comparing the CB-1 shock to VTR1000; 31mm which is too long

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2015_zpszp4nau94.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2015_zpszp4nau94.jpg.html)

Pic 2.  CBR900 compared to the other 2.  About same length as CB-1, good, but we are after something longer, so the search continues.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2016_zpsz7u0nltg.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2016_zpsz7u0nltg.jpg.html)

Pic 3. The washer size to get, got this one from Home Depot.  You can see how I cut it.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2017_zpsqwo1sm6a.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2017_zpsqwo1sm6a.jpg.html)

Pic 4.  Using a needle nose pliers to slip the washer on the shaft; the washer on the shaft.  It is like using a zip tie on the fork.  It is snug enough to sty where it is pushed, so it tells you (using the calibrated curve) what the max load is through the spring when setting sag + it tells you the max Net load (spring force minus compression damping force) when you ride,  Note: it captures only the max reading for that ride.  That is why you have to reset it every time you want to collect data.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2018_zpsfe4wzmof.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2018_zpsfe4wzmof.jpg.html)

Pic 5.  I didn't get all the time I wanted, so I only got the bike in position to collect the rake and trail data (tomorrow).  I have some homemade tools to do this.  Will post the results sometime this weekend.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2019_zps1hshpykw.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2019_zps1hshpykw.jpg.html)

I'm throwing a lot at you guys.  Let me know if something isn't clear and I'll see if I can answer any questions.

Jerry


Title: Re: CB-1 oem rear shock
Post by: ModerateFkr on June 15, 2017, 12:36:33 AM
I'm an empiric learner by nature Jerry, so my teachers don't get any apples. But you explain well, and I'm getting most of your process, and the theory all makes sense. Establishing our starting point is very valuable indeed. Plotting what actually happens on this specific model is crucial. Your contribution to the cause will be equal to that of the tuning guys in Canada, and actually of a great deal more practical use to more owners. I need to print out and read over a few times. First read is via my iPhone. If I lived near you I'd happily pop over to help. Hope the rest of your week goes well buddy.



Title: Re: CB-1 oem rear shock
Post by: a_morti on June 15, 2017, 02:56:03 AM
You're blowing my mind woth the detail,  and I'll re read this a few times before it sinks in. Very interested to see your findings in the end.

Worth noting 92-95 cbr900 shocks are longer than earlier years but have the same top and bottom fitment - they changed the design of the main frame. Do you know what model year you have there?


Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 15, 2017, 10:33:13 AM
Spacetiger:
what is the distance on the stock CB-1 shock eyelet to eyelet?
I've ordered a CBR900rr shock (93-95) and I'd like to know if that one is longer than the CB-1 length.

thanks,


Title: Re: CB-1 oem rear shock
Post by: Sugs on June 16, 2017, 12:10:35 AM
I have both shocks and just measured them.  CB-1 is 12 1/2 inches, maybe a shade under.  The CBR900RR is 12 5/8 inches, so an 1/8 or so longer or a little over 3mm.


Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 16, 2017, 12:13:34 AM
Thanks sir, that's what had recalled that they were indeed pretty close in length. I wonder if there is a different year 900rr shock other than 93-95 that is indeed much longer?
I have both shocks and just measured them.  CB-1 is 12 1/2 inches, maybe a shade under.  The CBR900RR is 12 5/8 inches, so an 1/8 or so longer or a little over 3mm.


Title: Re: CB-1 oem rear shock
Post by: ModerateFkr on June 16, 2017, 08:13:54 AM
Thanks sir, that's what had recalled that they were indeed pretty close in length. I wonder if there is a different year 900rr shock other than 93-95 that is indeed much longer?
I have both shocks and just measured them.  CB-1 is 12 1/2 inches, maybe a shade under.  The CBR900RR is 12 5/8 inches, so an 1/8 or so longer or a little over 3mm.

Is there a CBR900RR forum anywhere? I'm only able to get on the net via my phone, and it's very slow and frustrating right now, otherwise I'd check.


Title: Re: CB-1 oem rear shock
Post by: a_morti on June 16, 2017, 08:57:14 AM
I posted link just above with shock lengths listed. Off a street fighter forum, those guys are always looking for shock to fit a gap.


Title: Re: CB-1 oem rear shock
Post by: spacetiger on June 16, 2017, 11:39:03 AM
This maybe the last big post for a few weeks, the son is getting married in 2 weeks and there is much to do.

So, I’m getting ready to take some geometry measurements, so it’s time to dig out the home made stuff.

Pic1.  Here are the simple tools to check rake angle and trail measurements. The tool on the left is a simple laser pointer from office depot.  With 41mm fork tubes, the pvc piping is just the right diameter to clamp on to the leg.  Get the right spacer and a way to hold the laser pointer.  The app for the phone is 99 cents.  Make sure you zero it out on a level surface, then measure.  Simple.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2020_zpsvpifrvqe.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2020_zpsvpifrvqe.jpg.html)

Pic 2.  The laser is mounted on the left fork leg.  I had to disassemble it and add some spacers to get the right offset for the laser from the fork.  Rather than wait for the glue to dry, I used a hose clamp to hold the laser pointer.  On the right, you lay a board up against the fork with a perpendicular line down to the floor.  You line up a ruler to that line (I set the 10” mark even with the line).  Then, I hit the laser on when taking a measurement and the dot projects on the ruler; you can see it a bit after the 14” mark.  The measurements I will be taking are relative measurements and will be subtracted from the spec numbers.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2021_zps81ijrfzx.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2021_zps81ijrfzx.jpg.html)

Pic 3.  I’m only taking about 5 measurement sets.  Here is a pic half way through.  I jack up the rear and slide a board under the wheel (knowing the board thickness) then recheck the bike to make sure all is still square, then take the laser (trail) measurement and with the app, take the rake measurement.  

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2022_zps5jm1kdfv.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2022_zps5jm1kdfv.jpg.html)

Pic 4.  Here is the test data showing the affect of raising the rear on rake and trail; they both decrease.  I raised the rear 3.2” so I bound on both sides the target 1.3” change I am planning.  You can see the probable change in pic 4b

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2023_zpsdg6i9rc3.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2023_zpsdg6i9rc3.jpg.html)

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2024_zps2b8zbete.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2024_zps2b8zbete.jpg.html)

Pic 5.  I had done a CB700SC Nighthawk project a few years ago and changed the geometry of that bike (a lot).  To come out safely, I had to understand where the bike manufactures design their bike geometry, so I collected a lot of data from the magazines and tracked this on that project.  I recently added some small bikes and was considering getting an R3 but at the last minute I got the CB-1.  You can see where the oem geometry of the CB-1 is and where it is likely to move after putting in the [longer 0.32”] Frankenstein shock.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2025_zpsj9wsxist.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2025_zpsj9wsxist.jpg.html)

Pic 6.  How long is the CB-1 shock?  It looks like 12.4” or 315mm ETE.  Several years ago when people were more open, I happen upon an excel sheet kept on the YSS shock site.  I copied it and use it from time to time when looking for another oem shock.  Based on a length of 315mm, knowing I want to be 0.32” longer (or ~ 8mm), there are 60 possible options in the YSS database - sorry for the formatting on the possible shock options below.

Brand   Model   Year   Type   Length
 BMW    R 1100 S (rear)   '98>   MS   320
 BMW    F 650 GS / Dakar   '00-06   MS   330
 BMW    R 1200 C (rear) fork-type   '97-03   MS   330
 BMW    F 650 (Funduro)   '94-99   MS   315-325
 BMW    F 650 ST   '95-00   MS   315-325
 BMW    S 1000 RR   '11>   MS   315-325
 BMW    R 1100 S (rear)   '98>   MS   320-330
 DUCATI    748 SP   '94>   MS   310-320
 DUCATI    916 Strada   '94>   MS   310-320
 HONDA    VFR 800 F   '02>   MS   320
 HONDA    VFR 800 X   '2012   MS   320
 HONDA    CB 1000 R   '08-09   MS   310-320
 HONDA    CB 500 X   '13>   MS   310-320
 HONDA    CB 500 X   '13>   MS   310-320
 HONDA    CB400 F / CB 1   '89-90   MS   310-320
 HONDA    CBR 500 R/F   '13>   MS   310-320
 HONDA    CBR 500 R/F   '13>   MS   310-320
 HONDA    CBR 600 F   '99-00   MS   310-320
 HONDA    CBR 900 RR Fire Blade   '96-97   MS   310-320
 HONDA    NT 600 Hawk   '88-91   MS   310-320
 HONDA    VFR 1200 F   '10   MS   320-330
 HONDA    VFR 750 F   '94-99   MS   320-330
 HONDA    CBR 1100 XX Super-Blackbird   '97-07   MS   325-335
 HONDA    CBR 900 RR Fire Blade   '92-95   MS   325-335
 HONDA    VFR 800 FI   '98-01   MS   325-335
 HONDA    VTR 1000 SP I / II   '00-06   MS   325-335
 HYOSUNG    GT 650 S / R   '05-09   MS   315-325
 KAWASAKI    ZR 7 / S   '98-02   MS   320
 KAWASAKI    ZZR 1100   '90-92   MS   320
 KAWASAKI    ZZR 1100   '90-92   MS   320
 KAWASAKI    GPZ 900   '87>   MS   325
 KAWASAKI    GPZ 900   '87>   MS   325
 KAWASAKI    ZX 6 R Ninja   '95-97   MS   325
 KAWASAKI    GPZ 500 S   '87-03   MS   315-325
 KAWASAKI    GPZ 900 RZ Ninja   '84-86   MS   315-325
 KAWASAKI    GPZ 900 RZ Ninja   '84-86   MS   315-325
 KAWASAKI    ZX 10 R FOR RACING   '11>   MS   315-325
 KAWASAKI    ZX 250 R Ninja L5   < 08   MS   315-325
 KAWASAKI    ZX 250 R Ninja L5   < 08   MS   315-325
 SUZUKI    GSXR 1100 K / L / W H.5   '89-98   MS   320
 SUZUKI    GSF 1200 Bandit   '01-05   MS   325
 SUZUKI    GSXR 1000   '05-06   MS   325
 SUZUKI    VAN-VAN 125   '03>   MS   320-330
 SUZUKI    GSXR 1000   '07-08   MS   325-335
 TRIUMPH    Daytona 1200   '91-93   MS   315-325
 TRIUMPH    Daytona 900   '91>   MS   315-325
 TRIUMPH    Daytona Super III   '94>   MS   315-325
 TRIUMPH    Speed Triple / Trident 900   '94>   MS   315-325
 TRIUMPH    Sprint 900   '92-94   MS   315-325
 TRIUMPH    Trident 750   '92>   MS   315-325
 TRIUMPH    Trident 900   '92>   MS   315-325
 TRIUMPH    Trophy 1200   '92>   MS   315-325
 TRIUMPH    Trophy 900   '92>   MS   315-325
 YAMAHA    FZ 1 / Fazer   '06>   MS   320
 YAMAHA    TDM 900 (also ABS)   '02>   MS   330
 YAMAHA    YZF 600 R 6   '98-02   MS   310-320
 YAMAHA    TT 600   '00>   MS   315-325
 YAMAHA    FZ 1 / Fazer   '06>   MS   320-330
 YAMAHA    FZ 8   '10   MS   320-330
 YAMAHA    XZ 550 / S   '82-84   MS   320-330
 YAMAHA    XTZ 660   '91-94   MS   325-335

But, since I am making a Frankenstein shock, I can use any number of shocks…

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2026_zpsbiwxlc6c.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2026_zpsbiwxlc6c.jpg.html)

Pic 7.  I am done with the geometry testing, time to move to taking sag measurements.  Shock is installed with the washer.  Its hard to see, but the washer is there against the shock body.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2027_zpsrl3dvacc.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2027_zpsrl3dvacc.jpg.html)

Pic 8.  I roll the bike off the center stand and put down the side stand, then walk over to push the washer against the shock body as the bike comes off the center stand with a jolt.  Then, I roll the bike back on the center stand and remove the shock.  I want to make sure I get a good clean bike sag reading.  I actually do this twice to make sure.  In this pic, you can see the weight of the bike pushed the washer a fair amount given the total stroke of the shock is only 1.5”.  This is the bike sag measurement.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2028_zpskle84n14.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2028_zpskle84n14.jpg.html)

Pic 9.  This is the Rider sag measurement.  I do the same thing for pic 8 except I sit on the bike before rolling it back on the center stand.  Again I remove the shock to measure and yes, I did it twice; showing the same results.  The washer moved a lot!  I purposely stayed on the 1st preload indent so the spring only had the installed preload on the spring.  This made the spring the weakest, so the washer would move the most (for the most accurate measurement)

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2029_zpsjbjngh3u.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2029_zpsjbjngh3u.jpg.html)

Pic 10.  What does the sag testing mean?  In this pic, it is clear the shock as installed on 1st preload indent isn’t up to the task for me to ride on.  The rider sag is too much.  I also can see the ride sag load in 1,241 lbs.  My experience has been your expected top end capacity will need to be 2X or as much as 2.75X times the 1,241 lbs depending on the compression damping you have in the shock.  The more compression damping you have, the less spring rate (2X); the less compression damping, the more spring capacity you need (2.75X).  To keep from bottoming out, you will need to dial in all the preload on the oem shock.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2030_zps4rdmhay5.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2030_zps4rdmhay5.jpg.html)

Pic 11.  How the oem spring curve changes when you are on the last preload indent (you have compressed the spring an additional 0.363”).  You have more capacity,  but still look to be on the shy side still.  Until I ride the bike, I will not yet have a feel for how they set up the damping.  If I get the dyno ready to go, I will not have to rely on the riding data to help characterize the damping.  The easiest way to check the top end is to go out on the freeway and ride through a shallow “V” in the highway at about 70-80.  As you go through the “V”, roll on the throttle just before the V to make the rear squat a bit more, then at a safe spot, pull over and check where the nylon washer moved to.  That ride through the V will induce a slow speed piston movement in the shock, so the compression damping cannot help much, the work of the spring will be what holds you up.  I would be very interestd in getting this info from you guys.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2031_zpsosjf7wki.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2031_zpsosjf7wki.jpg.html)

Pic 12.  Know that I know what bike and rider sag loads look like, I can start playing with possible spring options.  ON first pass for my weight, it looks like a 1,600 lb/in spring rate might be close to working.  I am setting the rider sag point a bit lower than targeting (18% of shock travel vs. 20% planned)  but it gives me the top end I think I will need (depending on what damping scheme I end up going with).  Before finalizing the spring, I need to start looking at shock options.  If I can get more shock stroke (than 1.5”), I can use a lower rate spring.  So, time to get busy on that front…

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2032_zpst3mbdvie.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2032_zpst3mbdvie.jpg.html)

How are you guys coming on the nylon washers?

Jerry


Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 16, 2017, 11:42:53 AM
it's Friday here in the USofA sir.
I have to create my invoices and your information is blowin' me mind.
I'm going to have to digest all this tonight at midnight.....when my family members are dreaming of sugerplums dancing in their heads....

till then, you are B-AWESOME!


Title: Re: CB-1 oem rear shock
Post by: spacetiger on June 16, 2017, 12:00:20 PM
Thanks VH.

Note to all, I went through all of my previous post on this thread to clean up the pics.  I am on my home computer now and have better access to apps to make then cleaner.  I noted there was a small difference in a 1 curve fit (initially used my Apple to  do the curve fit), but seems its a bit different.  That has been modified to be consistent with all the other work done today.

Cheers.


Title: Re: CB-1 oem rear shock
Post by: ModerateFkr on June 16, 2017, 06:44:57 PM
Jerry, you've outdone yourself yet again bro, and there's far too much for me to respond adequately to now. And I haven't even found a nylon washer yet!!!

But you hit on an interesting point regarding the difference raising the back end has on the front fork geometry: essentially making it potentially 'quicker' like a race bike.

Given the expressed concerns about the potentially detrimental effect of 'raking out' the front forks by dropping them through the top yoke to create a street fighter style bike with straight bars, it seems you've pretty much answered the question that kept me awake last night. One will in effect counteract the other. You just get a taller CB-1 with very similar geometry, assuming the front forks behave in a similar way to the rear shock under load.

Does all that make sense? I'm thinking aloud here.


Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 16, 2017, 06:58:54 PM
I know all these threads regarding the rear suspension are all starting to bleed into one another.
I have a question:
It appears a 900rr rear shock spring only has a roughly 700# capacity because that spring and shock are meant to work with a "linkage" system.
Well, why can't you simple take the linkage system and bolt that (linkage included) to the CB1? I mean, sure you'll have to adjust the length but...wouldn't that work?
Is there some "magical" formula for a linkage setup on the rear shock I'm unaware of?
I mean...my 900rr shock, could that have been inserted on the CB1 rear suspension, linkage end inclusive?

I'm curious cause we are going thru mathematical and milling gymnastics to find an alternate suspension for the CB1 that wont break the bank.
Maybe I'm speakin' out my arse.......I don't know.


Title: Re: CB-1 oem rear shock
Post by: ModerateFkr on June 16, 2017, 07:55:16 PM
I know all these threads regarding the rear suspension are all starting to bleed into one another.
I have a question:
It appears a 900rr rear shock spring only has a roughly 700# capacity because that spring and shock are meant to work with a "linkage" system.
Well, why can't you simple take the linkage system and bolt that (linkage included) to the CB1? I mean, sure you'll have to adjust the length but...wouldn't that work?
Is there some "magical" formula for a linkage setup on the rear shock I'm unaware of?
I mean...my 900rr shock, could that have been inserted on the CB1 rear suspension, linkage end inclusive?

I'm curious cause we are going thru mathematical and milling gymnastics to find an alternate suspension for the CB1 that wont break the bank.
Maybe I'm speakin' out my arse.......I don't know.


I'm pretty sure that would entail more complicated work VintageHunter, probably modifying the mounting point. The objective is to find a shock or build a shock that does a better job than the stock shock (at full extension etc.) - with a heavier rider than the bike was intended for.

The way I understand it, this involves using a shock that is longer overall to raise the resting state of the rear end by a small amount (to allow for the extra weight take-up) adding plunger shaft free play (to account for the rider's extra weight in the shock), and a slightly stronger spring (again to account for the extra rider weight). All factors are required to create a fully satisfactory modification.

At least, that's my simplistic interpretation of what Spacetiger is saying. Indeed, it's the concludion I'd come to during my insomnia fuelled mental gymnastics. A longer, stiffer and longer travelling version of the one that satisfied the Japanese market ;)) Precisely how much longer, how much more travel, and how much stiffer for each rider's weight, is the objective of Spacetiger's work - for which he needs our input - for that personalisation bit.

Any linkage systems would involve radical modifications, and an even more complicated set of calculations that were never considered for this bike.

Hope this helps. Please put me right Jim if I've missed the point.


Title: Re: CB-1 oem rear shock
Post by: spacetiger on June 16, 2017, 11:21:35 PM
I know all these threads regarding the rear suspension are all starting to bleed into one another.
I have a question:
It appears a 900rr rear shock spring only has a roughly 700# capacity because that spring and shock are meant to work with a "linkage" system.
Well, why can't you simple take the linkage system and bolt that (linkage included) to the CB1? I mean, sure you'll have to adjust the length but...wouldn't that work?
Is there some "magical" formula for a linkage setup on the rear shock I'm unaware of?
I mean...my 900rr shock, could that have been inserted on the CB1 rear suspension, linkage end inclusive?

I'm curious cause we are going thru mathematical and milling gymnastics to find an alternate suspension for the CB1 that wont break the bank.
Maybe I'm speakin' out my arse.......I don't know.


I'm pretty sure that would entail more complicated work VintageHunter, probably modifying the mounting point. The objective is to find a shock or build a shock that does a better job than the stock shock (at full extension etc.) - with a heavier rider than the bike was intended for.

The way I understand it, this involves using a shock that is longer overall to raise the resting state of the rear end by a small amount (to allow for the extra weight take-up) adding plunger shaft free play (to account for the rider's extra weight in the shock), and a slightly stronger spring (again to account for the extra rider weight). All factors are required to create a fully satisfactory modification.

At least, that's my simplistic interpretation of what Spacetiger is saying. Indeed, it's the concludion I'd come to during my insomnia fuelled mental gymnastics. A longer, stiffer and longer travelling version of the one that satisfied the Japanese market ;)) Precisely how much longer, how much more travel, and how much stiffer for each rider's weight, is the objective of Spacetiger's work - for which he needs our input - for that personalisation bit.

Any linkage systems would involve radical modifications, and an even more complicated set of calculations that were never considered for this bike.

Hope this helps. Please put me right Jim if I've missed the point.


MF,

Great summary of the effort.  Its not just to scratch my itch, but do it in a way all rider of this bike can benefit.  The CB-1 is only a $2-4K bike.  It seems insane you have to spend 1/4- 1/3 the value of the bike just to put a decent rear suspension on it.  We have advanced so far, the yet the suspension aspect still seems to be more black art than straight forward engineering.  I think it is time to move this in that direction. 

By the way, I have been thinking about the end solution today for the CB-1.  When you fix one aspect, like the max shock stroke of 1.5", you box yourself in a bit.  When I was taking a hack at what would work, I quickly found I might need a pretty stiff spring for my weight.  If I continue down that path, riders over 200 lbs would really need some stiff springs.  The use of such stout springs drives the damping range of options because the damping has to handle the stiff spring too.  So, in this pic, I am exploring the lesser rate spring option because I allow for a longer shock stroke:

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2033_zpsfols9bpz.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2033_zpsfols9bpz.jpg.html)

I spoke of a Frankenstein shock because there is quite a bit of standardization out there within OEM makes, but also for aftermarket parts.  I do think it is possible to mix a few components to get what you want out of the final shock.  But, we shall see what is possible once I head down that path.  To date, the effort has been to just find another OEM shock that is affordable; perhaps adding a different spring and trying it out.  I think a different path might be possible….  Until my wallet crys uncle.

Jerry

 


Title: Re: CB-1 oem rear shock
Post by: ModerateFkr on June 17, 2017, 12:49:19 AM
This a noble cause Jerry. I for one appreciate it greatly. As soon as I sat on my bike before I bought it, but knew I was going to, I realised the back end was too soft for my fat ass. And at 220/225 in my gear I'm not actually that heavy, so I'm sure others are going to notice an even bigger difference.

I just had another thought about the taking out of the front end too. It's likely to slightly affect the weight on the front suspension - moving the forks form more vertical (due to lifting the back) to a less steep angle if the forks are dropped.

I'm aware that will alter the centre of gravity too. But I think we will be taking about 1" max when on the road. Now, if I can just find an aestheticly acceptable way to move my sitting position back 3", and possibly drop the footrests 1", I may have the perfect bike...!;)


Title: Re: CB-1 oem rear shock
Post by: a_morti on June 17, 2017, 03:36:26 AM
The idea of a longer travel shock certainly appeals, if it can be arranged for the ride height to be increased by the extra travel.


Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 17, 2017, 10:50:01 AM
I'm curious if the shock length increases from12-1/2" to 12-5/8"....what does that increase equate to with regards to increase ride height?
I know there's some formula that states if shock length increase by "X" amount then the ride height = "X" x ?


Title: Re: CB-1 oem rear shock
Post by: spacetiger on June 17, 2017, 03:43:22 PM
VH,

The equation is in one of the graphics; Y = -0.727424x2 + 3.940181x + 0.005984 where “x” is a negative term (-1/8 in your example) and Y is the amount the rear compress (axle moves up).  So, here are a few X and Y numbers:
shock  axle
 1/8     0.49”
 1/4     0.95”
 1/2     1.79”
 1        3.22”
So your question on a 1/8 shock change = .49” longer


Can one of you guys verify the air gap from ground to bottom of the rear tire?  I show 1.5” on my square rear tire.  I misread the measurement and thought it was 1.75” earlier, so I have less space to stretch the shock than I thought previously.  My pic of the tire:
(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2034_zpshszkqblx.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2034_zpshszkqblx.jpg.html)

MF,
I didn’t catch your earlier post on the front.  You are right, if you move the forks down (making them “longer”) then it does offset the lifting in the rear – depending on how much you raise them.  With the app, you could measure the net change and know where you are.  

It is a different story if you slip the forks up effectively shortening them.  I would be cautious about doing this unless you are measuring the change and know where you are.  The rear change alone puts the bike near the leading edge for the current bikes coming out.  The one thing about the newer bikes in that rake/trail neighborhood is that they only compress the front suspension about 4” or less.  The stock CB-1 front suspension has 5.1” of travel – that is inclusive of the top out spring, so it is less than 5 , perhaps  4.5” or so.  To stay out of trouble, I would limit the travel to 4”.  You get this if you are moving to a cartridge setup, otherwise, you will have to add a small spacer between the damper rod and top out spring.  The spacer should be equal to the length you are trying to reduce the fork compression distance.  And for sure, you need to make sure the front springs are set up for your weight. The point is that you do not want the nose of the bike to compress over too far with the rear sticking up.  You could get into an unstable front wheel wobble that ends up with you eating asphalt.  


Title: Re: CB-1 oem rear shock
Post by: ModerateFkr on June 17, 2017, 09:13:41 PM
Quote
MF,
I didn’t catch your earlier post on the front.  You are right, if you move the forks down (making them “longer”) then it does offset the lifting in the rear – depending on how much you raise them.  With the app, you could measure the net change and know where you are.  

It is a different story if you slip the forks up effectively shortening them.  I would be cautious about doing this unless you are measuring the change and know where you are.  The rear change alone puts the bike near the leading edge for the current bikes coming out.  The one thing about the newer bikes in that rake/trail neighborhood is that they only compress the front suspension about 4” or less.  The stock CB-1 front suspension has 5.1” of travel – that is inclusive of the top out spring, so it is less than 5 , perhaps  4.5” or so.  To stay out of trouble, I would limit the travel to 4”.  You get this if you are moving to a cartridge setup, otherwise, you will have to add a small spacer between the damper rod and top out spring.  The spacer should be equal to the length you are trying to reduce the fork compression distance.  And for sure, you need to make sure the front springs are set up for your weight. The point is that you do not want the nose of the bike to compress over too far with the rear sticking up.  You could get into an unstable front wheel wobble that ends up with you eating asphalt.  


Thank you for the confirmation and extra info Jerry.

I definitely am only looking at lengthening the forks. The problem us I don't have a decent flat surface where the bike is stored. I may need to do proper measurements later.

I'm sure your squared off tyre will be making a difference. It will most likely be equal to the difference between the centre tyre depth and new centre tyre depth. So, unless yours is illegal, maybe not so much. 1/8-3/16" perhaps?

Feels strange to be thinking in imperial fractions again. I began training in aircraft engineering in the UK just at the point when all drawings were in both imperial and metric, with the latter expressed with a comma for the decimals! That was 1974. I find seem to be able to find another living soul who remembers that system.

But at a tool sale a few years back I bought a 1 meter metric steel rule in great condition that has the UK war department mark and the date 1940! But that's another story.


Title: Re: CB-1 oem rear shock
Post by: spacetiger on June 20, 2017, 08:50:42 PM
still waiting for data from the group...

Currently looking at options with existing stock. 

Option 1.  CBR900
  +'s: wide body shock that takes the 40mm piston; has LS compression damping via remote reservoir
   -'s:  need to lengthen the lower clevis (doable with the VTR lower clevis I believe); 900 stroke is just 2" with no stopper.

Option 2.  2006 BMW K1200R ($34 shipped) shock made by WP (this is a quality piece, much better craftsmanship than the 10 year older Showa)
  +'s: wide body shock that takes the 40mm piston, already 0.65" longer (a bit too long, but this can be reduced with internal spacers), easily has the 2" stroke (!); remote preload adjuster (I'm cheating here as I have a remote preload adjuster from another project).
  -'s:  no compression damping (but can be added via CBR600 shock for peanuts); have to drill and tap a fitting for remote reservoir

Option 3.  Modify the CB-1 shock
  +'s: wide body shock that takes the 40mm piston
  -'s:  no compression damping (but can be added via CBR600 shock for peanuts); have to drill and tap a fitting for remote reservoir; no rebound damping, so you need the VTR clevis

All options require you to acquire 2 other donor shocks; the good news is they can both be had for ~$75.  That would put the rear shock at about $75 + $120 (RT piston/shims) + $90 (new spring) + $50 misc bits) = $335, maybe $400 if I need a few more bits.  For that $ I get a shock the right length with remote preload adjuster, with a dialed in damping (RT piston) with further adjustability via remote LS compression and rebounding damping.    You can buy a YSS shock close to this and it will come with the longer ETE length and rebound damping (only).  You don't get remote preload adjuster (unless you pay more) and no compression damping + you get the piston shim stack they pit in.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/IMG_4905_zpsybwbfowl.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/IMG_4905_zpsybwbfowl.jpg.html)

But I still looking...

How are you guys coming along with the washer?  I need some data.

Jerry


Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 20, 2017, 09:04:26 PM
My washer data is a no go. I made the decision to go w the CB1 spring Inserted into a 900rr shock.
I'm pleased so far w new "feel" of the CB1.


Title: Re: CB-1 oem rear shock
Post by: spacetiger on June 20, 2017, 09:42:18 PM
VH,

That's abut the best $30 upgrade you can make as you get some aspects of 2 of the 3 the things I am aiming for but you did it for 1/10 I'm going to spend:
- it is about 0.2" longer ETE shock - that should raise your rear by about 0.765" (about half what the gap between the tire and ground)
- the oem spring mounted in the CBR body has about .85" of preload (more than oem preload on oem spring).  For your weight VH, I suggest you dial in all the indents of preload.  That will compress all of the lower rate coils of the spring and have you completely riding on the higher rate spring - That way you are riding on a 1,239 lb/in spring.  That is a better match to your weight.
- You picked up a bit more on the shock stroke (its more than 1.5" but probaby a tad shy of 2.0".

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/IMG_4907_zpsyju6dj1v.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/IMG_4907_zpsyju6dj1v.jpg.html)

I'd still advise you to slip a washer in there to see if you are bottoming out.

On a different note, if you can feel a difference in the before and after than I would say the shock spring you had mounted in the NT650 was NOT stout enough as you should have noticed a bigger difference that you are saying you got on the CB-1 change.  Of course, the mind has a way of telling you it is better...  But I would tell you is better.




Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 20, 2017, 10:53:17 PM
spacetiger:
thanks. total cost to me was $100.
that was about $20 for the spring and about $80 for swapping out the CB1 spring into the 900rr shock and having the suspension specialist mount it up and dial it in.
He (the suspension guy) told me that if I wanted that newly created 'Franken-shocK" (CB1 spring in a 900rr shock assembly) that he could rebuild it for another $100 and it would basically be brand new.
He said "all" the parts are available to rebuild it.

When I have the next $100 to use up....I may just take it back to him to get that done.
In the interum......the CB1 does indeed "feel", not quite sure how to describe it......more.....solid? if that's any description at all? More.....firm(er) of a ride? Not as "marshmellowy" of a feel? it's hard to put into words really what I'm sensing now on the CB1 ride.


Title: Re: CB-1 oem rear shock
Post by: spacetiger on June 20, 2017, 10:59:25 PM
Do you have any pics?  Seems like you should write this up so there are different price point options available to the CB-1 community.  I think you meant $20 for the shock (vs spring)?  And you paid $80 for the guy to swap springs then he "set" it up (set initial preload and damping adjustments) for you?

If you write it up, I'll add a piece to show you how to swap out springs using 4 ratchet straps (safer than 2).  That might cost you $50 bucks for the straps, but you have them to use again.

Jerry


Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 20, 2017, 11:02:38 PM
Pictures? of the 900rr shock? I have the pictures of the shock and model year.
I can take some pictures this weekend of the shock mounted to the CB1 with reservoir location as well.
I was a bit worried that there was no place for that remote reservoir with the stock (short) hose but it fits fine where it is.
I'll take some pictures and put together a little write up of what was told to me by the tech so you all can have that info as well.
I know when I was looking for a possible rear shock replacement I had to hunt and peck thru many threads and many forums to find the info I was looking for.
Perhaps if its all in this one thread that'll serve as a great starting point with your mathematical and analytical information too, for anyone else looking for shock options.


Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 20, 2017, 11:04:01 PM
yes....$20 for the entire 900rr shock in its OEM form.
then $80 or the tech to do his spring swap (CB1 spring into the 900rr shock - obviously removing the 900rr OEM spring during this process).
Do you have any pics?  Seems like you should write this up so there are different price point options available to the CB-1 community.  I think you meant $20 for the shock (vs spring)?  And you paid $80 for the guy to swap springs then he "set" it up (set initial preload and damping adjustments) for you?

Jerry


Title: Re: CB-1 oem rear shock
Post by: a_morti on June 21, 2017, 04:55:30 PM
Unfortunately I can't help, mine has a Cbr arm and Hagon shock. The shock is tired though, the top bush is worn and I'm not sure there's a simple way to fix it. So very interested in your research here.


Title: Re: CB-1 oem rear shock
Post by: ModerateFkr on June 21, 2017, 10:42:15 PM
still waiting for data from the group...

Currently looking at options with existing stock. 

Option 1.  CBR900
  +'s: wide body shock that takes the 40mm piston; has LS compression damping via remote reservoir
   -'s:  need to lengthen the lower clevis (doable with the VTR lower clevis I believe); 900 stroke is just 2" with no stopper.

Option 2.  2006 BMW K1200R ($34 shipped) shock made by WP (this is a quality piece, much better craftsmanship than the 10 year older Showa)
  +'s: wide body shock that takes the 40mm piston, already 0.65" longer (a bit too long, but this can be reduced with internal spacers), easily has the 2" stroke (!); remote preload adjuster (I'm cheating here as I have a remote preload adjuster from another project).
  -'s:  no compression damping (but can be added via CBR600 shock for peanuts); have to drill and tap a fitting for remote reservoir

Option 3.  Modify the CB-1 shock
  +'s: wide body shock that takes the 40mm piston
  -'s:  no compression damping (but can be added via CBR600 shock for peanuts); have to drill and tap a fitting for remote reservoir; no rebound damping, so you need the VTR clevis

All options require you to acquire 2 other donor shocks; the good news is they can both be had for ~$75.  That would put the rear shock at about $75 + $120 (RT piston/shims) + $90 (new spring) + $50 misc bits) = $335, maybe $400 if I need a few more bits.  For that $ I get a shock the right length with remote preload adjuster, with a dialed in damping (RT piston) with further adjustability via remote LS compression and rebounding damping.    You can buy a YSS shock close to this and it will come with the longer ETE length and rebound damping (only).  You don't get remote preload adjuster (unless you pay more) and no compression damping + you get the piston shim stack they pit in.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/IMG_4905_zpsybwbfowl.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/IMG_4905_zpsybwbfowl.jpg.html)

But I still looking...

How are you guys coming along with the washer?  I need some data.

Jerry


I'm playing catchup here Jerry. Very impressed by your findings.

Just one question at this point, have you totally discounted the Blackbird shock? If so, is it because it's too long? too soft? or something else.

I'm still hoping Nicknitrous will report in with his experience of the Bb solution. Whilst they're possibly not perfect, they do seem to fit without needing any mods - if what we believe to be is true. 



Title: Re: CB-1 oem rear shock
Post by: spacetiger on June 22, 2017, 12:03:30 AM
Thanks MF.

A little more today after work; trying to see how well the BMW shock fits into the bike even though it’s a bit too long.

1st adjustment is to sand down the upper shock mount width so the top mount will fit into the bike.  That takes a few minutes on the belt sander.  Then I slip the nylon washer onto the shock and put the shock into the bike.  Because the shock is a tad long, I slip a 0.32” thick piece of wood under the rear tire, then lower the rear wheel down to fully rest on the wood.  I then remove the shock and I can see how much the shock compressed to fit into that space with the wheel almost down; About 0.43” too long.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2035_zps14jtgphi.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2035_zps14jtgphi.jpg.html)

I trim a little of the rubber stopper off and can see there will be plenty of room to leave a bit over 2” of shock stroke even after removing the 0.43 additional length.  I will either use internal spacers or machine the shaft /rebound adjuster rod.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2036_zpsflqufqz4.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2036_zpsflqufqz4.jpg.html)

It is still looking promising, so I get the box of suspension bits and start putting the 1st version of Frankenshock together.  Since I had a 1,300 lb/in spring from a Nitron shock (6” long), I had to cobble together a spacer to fit between the top of the spring and the bottom of the preload adjuster.  As shown, there is no preload on the spring as I have to compress the shock a bit to get it into the bike. 

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2037_zpsi4slkmh3.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2037_zpsi4slkmh3.jpg.html)

After getting the shock into the bike I tighten down the upper spring perch (ring) as snug as I can get it, then dial in all the preload from the adjuster.  Now,  look for clearance issues; the top and sides look good.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2038_zps7ufbz2xr.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2038_zps7ufbz2xr.jpg.html)

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2039_zpsyljix0wp.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2039_zpsyljix0wp.jpg.html)

So I put on the seat as I think it will not be an issue.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2040_zpscsuy6xvv.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2040_zpscsuy6xvv.jpg.html)

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2041_zpspbhxe10n.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2041_zpspbhxe10n.jpg.html)

The last thing to check is the gas tank with seat…. And it still fits.  This means I do not have to use the remote adjuster (I was saving it for another bike I am working on).  This isn’t the most handy adjuster as you have to take the seat off to really get a hold of the knob – but you only have to do it when you want to set up the bike for some spirited runs.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/rear%20shock%2042_zpsz97wlybn.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/rear%20shock%2042_zpsz97wlybn.jpg.html)

I rolled the bike off the centerstand and sit on  the bike, it feels so much better than before.

The next step will be to call RaceTech to see what the right piston kit to order.  I also need to source a T-fitting so I can drill and tap a hole into the disassembled shock body for a oil/N2 fill port via a schrader valve and on the other end a mounting point for the remote reservoir.  If I can get a gold valve kit (40mm I think), then I will stay with this shock until I run into a showstopper.

For all of you looking at the VTR1000 shock, you can continue to do so, but I don’t think it is a very good option for several reasons.  The biggest reasons:
1. It is way too long.  You can see from the pics I posted of it next to the oem shock that is much longer.  The BMW shock is only a bit longer than oem and it is too long.
2. It uses a narrower shock body, so it will have use a smaller piston inside (I am guessing 35mm).  This means it’s oil flow potential will not be as good as the BMW, CBR900, or OEM shock that [probably] use a 40mm piston.  The higher flow potential of the larger ports in the piston means you have a greater range of options to tune the shim stacks.  I would like to have a 2 stack on the compression side for low speed and highspeed.  Even though I will only have LS adjustability, I can still set the HS compression stack to give me a way to blow off the HS impacts.
3. The upper spring perch is narrow, so this shock uses a tapered spring on one end.  Aftermarket springs will require an adapter (and you will need a new spring as the VTR spring isn’t nearly stout enough.
4. Stroke might be a little shy of 2”
5. Limited spacing up top to drill and tap a hole for a remote reservoir
6. Did I say it too long??, well, its too long. 
7. Did I mention it is too long?

If you are not going to open the shock up and will live with the damping a bit off (although you can make some adjustments on the compression and rebound side) and swap the oem spring in (or put the right spring in for your weight), it is going to be hard to overlook the CBR900 as the viable swap option.  It is even a bit longer than oem, a good thing as it raises the rear up about 0.75".  For me, I need a longer shock, stroke, and want easier preload adjustability so I'm likely to stay with the BMW (WP shock).

Jerry


Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 22, 2017, 09:24:20 AM
Great job Jerry.
you've done an awesome job of methodically going thru the motions of figuring this thing out.
Nice Nice work.
Your attention to details show.

That large black knob adjuster looks like it was made to fit just right.

You'll have to tell us how the CB1 now feels on the road once you get it all dialed in.

Again, superb analysis.


Title: Re: CB-1 oem rear shock
Post by: ModerateFkr on June 22, 2017, 02:47:06 PM
I like they solution too Jerry. Very nice fit. Now we have two options.


Title: Re: CB-1 oem rear shock
Post by: VintageHunter on June 22, 2017, 10:55:23 PM
Spacetiger:
you should seriously consider "making" a few of these "Frankenshocks" for the CB1.
I may just consider purchasing one from you sir. ;)




Title: Re: CB-1 oem rear shock
Post by: spacetiger on June 29, 2017, 09:03:21 PM
I have been trading some PM's with MF, but think this should be out in the open so all can benefit.

The discussion has been on shocks, springs, and what can be swapped (Springs) [to what gain].  I went down to check and test the CBR900 and VTR1000 shock/springs.  I do not have a BB shock, but believe the spring spec may be the same as the VTR shock.  In any case, here are the numbers:

             IL          FL     Preload         ID          WR
CB-1    6.449"   7.044"   0.595"     2.00/2.25    1.53"
cbr900 6.099"   6.515"   0.416"     2.00/2.25    1.90"
VTR     7.887"   8.375"   0.488      1.82/2.25    2.03"

IL = Spring installed length
FL = Spring free length
Preload = initial spring preload distance (FL - IL)
ID = spring inside diameter (the 2 numbers are the distance on 1 end, and the other number is the other end)
WR = max stroke of the shock

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/IMG_5148_zps7bkjllyi.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/IMG_5148_zps7bkjllyi.jpg.html)

Then I tested the CBR spring and VTR springs.  The spring only test is shown with the CB-1 spring.  The green line (CBR 900) is the weakest of the 3; a close linear approximate rate is 787 lbs/in.  The brown line is the VTR spring; a close approximate linear rate is 884 lbs/in.  Although I cite a linear rate, both springs are progressive rate springs.  Tested as springs with no preload, the springs with the most capacity are the VTR and CBR springs because they will compress over a longer stroke (2.03" and 1.9" respectively).  The CB-1 spring has more stout linear rates (923 and 1,239 lbs/in) but it is set up to work over a 1.53" stroke, so it has less top end performance.

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/IMG_5153_zps50tliw66.png) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/IMG_5153_zps50tliw66.png.html)

Now, look at the performance of the spring once you compress the spring onto the shock.  The solid green line (CBR) only compress the spring the least amount at 0.416" so with the weaker spring, it tops out at 1,924 lbs after a 1.9" stroke.  The CB-1 red/blue line is the oem spring.  it tops out at a max of 2,302 lbs.  So, unless you weigh very little, you cannot just swap out the CB-1 shock for the CBR shock.  If the BB shock is like the VTR, it may have a tad more top end capacity than the CB-1 shock (2,348 lbs vs. 2,302 lbs).  In this case, the longer 0.5" VTR stroke (2.03" vs 1.53") allows it to be similar in capacity to the CB-1 shock.  So, if you can get by with the OEM shock, then the BB shock might be a direct swap.  Then there is an option to the CBR shock.  If you remove the oem spring and pop in the CB-1 spring, you gain a lot of top end capacity as depicted by the dashed green line.  This hybrid combination compress the CB-1 spring 0.945", almost fully compressing the lower rate portion of the spring.  Then you operate on the higher rate (1,239 lbs/in) out to the max stroke distance of 1.9".  Your new top end capacity is 3,189 lbs.  That is a 38.5% increase, probably enough to cover most riders.  I cannot be sure because that shock combination will be under damped, so compression damping will not help you much on initial compression.  If you are a heavy rider using this combination, you should be adjusting the low speed compression damping to give you more resistance - but it may not be enough as the CB-1 top rate is 57% stiffer than the CBR spring ( the compression damping has to make up a lot for that big a difference.  This is where the nylon washer can help guide you on what setting to use; so start with max and dial back if it is too harsh.  That said, it is possible to get a proper 7" x 1,200 or 1,300 lb/in linear rate spring in the CBR shock and get better long term performance as the CB-1 spring will weaken over time.  If you run a linear rate spring, the ID will both be 2.25" - so you will need a spacer for one end.  The CB-1 spring swaps in because it has the same diameters at each end as the CBR shock.  Since noone will be collecting nylon washer data, I run this combination as I work on the Frankenstein shock and report back what I'm seeing.  

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/IMG_5154_zpsmpnpftjg.png) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/IMG_5154_zpsmpnpftjg.png.html)

You guys have to tell me if this is only as clear as mud buy telling me what you do not understand.  I'll try to clarify the parts you don't track.

Jerry


Title: Re: CB-1 oem rear shock
Post by: a_morti on June 30, 2017, 03:27:54 AM
It's making sense to me so far.

I think the vtr shock can more or less be laid to the side. It's too long and there's not much to gain.

The one which is missing is the blackbird shock. I appreciate it's not about money for you, but how would you feel if a forum member were to score a cheap BB shock and ship it to you?


Title: Re: CB-1 oem rear shock
Post by: spacetiger on June 30, 2017, 06:20:48 AM
If someone does that that, I'll test it too.  That includes damping once my adapter pieces come in a month or so.  Just PM me whoever wants to do this.


Title: Re: CB-1 oem rear shock
Post by: Sugs on July 02, 2017, 07:12:46 PM
still waiting for data from the group...

OK, finally managed some sag measurements on the stock CB-1 shock, no preload.  My bike is a '90 with zero mods.

7.5mm bike only, 17.5mm with me.  I weigh 198.6lbs.

Hope this helps you out.


Title: Re: CB-1 oem rear shock
Post by: ModerateFkr on July 02, 2017, 08:22:47 PM
Some of the valve and shimming references are a bit of a mystery to me Jerry, but that's because I haven't looked at one of these shocks in detail yet, plus I'm still reading your posts on my phone.


Title: Re: CB-1 oem rear shock
Post by: spacetiger on July 02, 2017, 10:20:37 PM
still waiting for data from the group...

OK, finally managed some sag measurements on the stock CB-1 shock, no preload.  My bike is a '90 with zero mods.

7.5mm bike only, 17.5mm with me.  I weigh 198.6lbs.

Hope this helps you out.

Awesome Sugs, can you confirm for me what preload setting you are on?  I noted your bike sag measurement didn't move quite as far as mine, so I'm guessing you are not on the 1st shock preload indent, perhaps the 2nd one?

I am also guessing you have a stock bike?


Title: Re: CB-1 oem rear shock
Post by: Sugs on July 03, 2017, 12:20:34 AM
Awesome Sugs, can you confirm for me what preload setting you are on?  I noted your bike sag measurement didn't move quite as far as mine, so I'm guessing you are not on the 1st shock preload indent, perhaps the 2nd one?

I am also guessing you have a stock bike?

I made sure I was on number one preload and was unable to turn it any further.  Might be my spring is a little fresher, or its the 1.8lbs lithium battery that made the difference.  Seat isn't stock but unless the stock one has a metal seat pan that shouldn't be much difference.  Tank is about 2/3-3/4 full of gas.


Title: Re: CB-1 oem rear shock
Post by: spacetiger on July 03, 2017, 11:38:34 PM
Sugs,

Here is what your data means (so far)

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/7ac2a241-b3e4-495b-8507-4e03dbe9a049_zpsibhxnvto.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/7ac2a241-b3e4-495b-8507-4e03dbe9a049_zpsibhxnvto.jpg.html)

My data is in row 90 (#1) and your data is in row 91 (#2).  In column R, i used the spec weight of the bile with full tank (414 lbs).  Having taken a scale and measured the weight under the rear tire, then front tire, I could see what the weight distribution was on the rear.  That value is in column s (0.508), so for my case, 0.508 x 414 lbs = 210 lbs.  For Sugs, I took 4lbs off for battery + 1 gal of gas; so 11 lbs off my 414 lbs for 204 lbs at rear.

My bike sag nylon washer reading was 0.327", Sugs was 0.298" (7.5mm).  Using the calibrated curve, that translates out to 854 ls for me and 825 lbs for Sugs.  I'm looking for the measured ratio of measured weight through spring vs. rear weight.  In my case it is 854/210 = 4.072.  For Sugs it is 825/204 = 4.041.  The average of the data is the yellow cell at 4.056.  This is the important ratio we need to start characterizing loads we are seeing.

On bike sag, my weight is 180 x 0.508 = 91 lbs at rear.  For Sugs it is 199 x 0.508 = 101 lbs.  Using the yellow cell average, that translates out to 91 x 4.056 = 271 lbs and for Sugs it is 101 x 4.056 = 411.  Adding those calculated values to the calculated bike weight through the springs values in column W, you get the calculated rider sag load of 1,222 lbs for me and 1,239 lbs for Sugs (these values are found in column AF).  So far the model is reasonably accurate, within 2% on only 2 data sets.  I think 2 more should lock in the accuracy.

So how do you use it?  In row 95 is a theoretical 160 lb rider and in row 96 is a 220 lb rider.  Both riders have a stock bike.  So if the gas tank is full, you can calculate the rider load and compare it to a measured nylon washer reading.  For the 160 lb rider, his rear load is 160 x 0.508 = 81 lbs.  Multiply that number by 4.056 and get 330 lbs; add that to bike load of 851 lbs and get 1,180 lbs.  Using the spring curve on 1st indent, that rider should get a nylon washer reading of .625".    The 220 lb rider would see 0.725".

Now we need some riding data (Sugs).  Just ride the bike.  If you can take a washer reading after riding sedately on the freeway and one from easy ride on surface streets (but hit a few pot holes), you should have the bare minimum data to start compiling how to set up the rear suspension using stock spring.  I'll post my riding data once I get the carbs cleaned enough to run the bike.

The model could also benefit from data from a 160 lb or 220 lb rider, but I'll take any data.  We just need 2 more guys to play.

Jerry


Title: Re: CB-1 oem rear shock
Post by: ModerateFkr on July 03, 2017, 11:58:09 PM
Jerry, I'm in awe and actually feeling guilty for not having my bike on the road.

But it now seems that by experiencing these various delays, I may have avoided a potential catastrophic disaster. If indeed I do have a broken ring, I could be sitting in a casualty ward right now. That's a sobering thought. It's becoming increasingly clear the PO knew all about the problem with the engine and took extensive steps to disguise it. Not impressed.

There may be a long delay before I can give you road data I'm afraid.


Title: Re: CB-1 oem rear shock
Post by: Sugs on July 04, 2017, 01:07:25 AM
Now we need some riding data (Sugs).  Just ride the bike.  If you can take a washer reading after riding sedately on the freeway and one from easy ride on surface streets (but hit a few pot holes), you should have the bare minimum data to start compiling how to set up the rear suspension using stock spring.

I'm guessing you would want the ride data on the lowest preload too?


Title: Re: CB-1 oem rear shock
Post by: spacetiger on July 04, 2017, 01:40:37 AM
No. You need to be up on preload or you will bottom out. I'm guessing 6th or 7th indent. Just let me know which one you rode on. I know how to adjust curve.  I plan on riding on 7th indent.

Jerry

Pic Test

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/IMG_5166_zpspnszltum.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/IMG_5166_zpspnszltum.jpg.html)

Seems I can post a pic, lets see how long it lasts...  seems it lasts 1 day

test 2:  which one lasts...start at 10 pm est:  
(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/Honda_zps4zs30tbo.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/Honda_zps4zs30tbo.jpg.html)

http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/Honda_zps4zs30tbo.jpg

Update:  By 07:45 next day, 3rd party hosting was lost, but link back to PB still works.
Update to update:  as soon as I tested the link and posted the update comment, the 3rd party hosting link now shows the pic again?


Title: Re: CB-1 oem rear shock
Post by: ModerateFkr on July 15, 2017, 12:20:31 PM
No. You need to be up on preload or you will bottom out. I'm guessing 6th or 7th indent. Just let me know which one you rode on. I know how to adjust curve.  I plan on riding on 7th indent.

Jerry

Pic Test

(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/IMG_5166_zpspnszltum.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/IMG_5166_zpspnszltum.jpg.html)

Seems I can post a pic, lets see how long it lasts...  seems it lasts 1 day

test 2:  which one lasts...start at 10 pm est:  
(http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/Honda_zps4zs30tbo.jpg) (http://s93.photobucket.com/user/spacetiger81/media/CB-1/Honda_zps4zs30tbo.jpg.html)

http://i93.photobucket.com/albums/l80/spacetiger81/CB-1/Honda_zps4zs30tbo.jpg

Update:  By 07:45 next day, 3rd party hosting was lost, but link back to PB still works.
Update to update:  as soon as I tested the link and posted the update comment, the 3rd party hosting link now shows the pic again?

Photobucket has turned into a gigantic spam turd! I followed your link just now and I got a page offering me those stupid clickbate 'stories' of the world's ugliest people and what the world's most irrelevant people look like after losing weight.

They then flashed up an ad for going ad free, and a link to a policy statement that had no comments. Why? There didn't appear to be a comments option!!

Companies like that deserve to destroy themselves with their horrible business models and greed. I'm not saying Google/YT is any better, but at least the vid hosting thing works - as they surveil our every activity on behalf of the CIA/NSA/GCHQ globsl banking/war complex.

Could the owners and moderators of this site please pass my consudered thoughts to the fools at Photobucket? Remind them that business is about relationships. Thank you.



Title: Re: CB-1 oem rear shock
Post by: a_morti on November 20, 2017, 05:15:11 PM
Was just looking back over this thread as I got my CBR1100XX shock installed. As expected, it has a lighter spring than stock, but so far it seems usable. I can't find a C spanner to add preload, but that's definitely the first thing it needs as it drops a lot coming off the stand.

I haven't yet noticed it bottom out but I've only ridden round town, this may be because it also has a longer stroke than stock. I haven't measured that scientifically, but for sure the bike starts at higher ride height (wheel nearer ground on centre stand) and still goes down to around about stock level at full compression. Seems legit that if you have more wheel travel, you can use a softer spring?

If you use Chrome browser, this extension will fix the Photobucket issues. If you don't use Chrome, start using it and get this extension!
https://chrome.google.com/webstore/detail/photobucket-hotlink-fix/kegnjbncdcliihbemealioapbifiaedg`

I wondered idly if you could easily extract the hydraulic preload adjuster off a VFR750 shock.
(http://timoto.com/Photos/shock-absorber-showa-:37.5cm-Honda-VFR-750-(RC36-1)-(90/93)-35348.JPG)

According to the Penske site (https://www.penskeshocks.com/wp-content/uploads/2017/03/PENSKE-SPRING-APPLICATION-CHART.pdf), that shock has a similar spring rate requirement to the CB-1, so if I could get the adjuster and the spring off a cheap one and fit it to my Blackbird shock, I could have my own cheap version of your Frankenshock.


Title: Re: CB-1 oem rear shock
Post by: a_morti on December 09, 2017, 03:37:36 PM
I found a C spanner, and added preload to 17 turns of thread showing above the locknut. It now sags about 15mm off the bike's own weight, but I wasn't able to get a measurement with me sat on the bike yet (no assistant).

The spring is perhaps softer, but considering the shock has longer travel, I think those factors cancel out? In any case, the bike rides nicely and has compliant damping. It doesn't seem to be anywhere close to bottoming out, but unfortunately the plastic sheath over the chrome rod means I can't get a washer in there to check.

It's only a basic shock but it rides well enough, has at least some (enough) damping control, was cheap, and is a lot newer than any used original CB-1 shock. Overall, I'm happy :)