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Author Topic: CB-1 oem rear shock  (Read 1871 times)
ModerateFkr
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« Reply #45 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.
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spacetiger
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« Reply #46 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.



But I still looking...

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

Jerry
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VintageHunter
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« Reply #47 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.
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spacetiger
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« Reply #48 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".



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.


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VintageHunter
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« Reply #49 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.
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spacetiger
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« Reply #50 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
« Last Edit: June 20, 2017, 11:04:32 PM by spacetiger » Logged
VintageHunter
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« Reply #51 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.
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VintageHunter
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« Reply #52 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
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a_morti
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« Reply #53 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.
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ModerateFkr
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« Reply #54 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.



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. 

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spacetiger
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« Reply #55 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.



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.



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. 



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.





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





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.



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
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VintageHunter
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« Reply #56 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.
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ModerateFkr
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« Reply #57 on: June 22, 2017, 02:47:06 PM »

I like they solution too Jerry. Very nice fit. Now we have two options.
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« Reply #58 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. Wink


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« Reply #59 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



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.



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.  



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
« Last Edit: June 29, 2017, 09:21:26 PM by spacetiger » Logged
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