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Author Topic: CB-1 oem rear shock  (Read 1837 times)
Sugs
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« Reply #30 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.
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« Reply #31 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.
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« Reply #32 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.
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« Reply #33 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.
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« Reply #34 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.



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.



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.  



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





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.



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…



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.



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.



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)



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.



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.



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…



How are you guys coming on the nylon washers?

Jerry
« Last Edit: June 16, 2017, 11:41:51 AM by spacetiger » Logged
VintageHunter
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« Reply #35 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!
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« Reply #36 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.
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« Reply #37 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.
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« Reply #38 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.
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« Reply #39 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 Wink) 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.
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« Reply #40 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 Wink) 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:



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

 
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« Reply #41 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...!;)
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« Reply #42 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.
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« Reply #43 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 ?
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« Reply #44 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:


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.  
« Last Edit: June 17, 2017, 03:51:09 PM by spacetiger » Logged
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