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Author Topic: CB1 900rr shock - my write up  (Read 639 times)
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« on: June 25, 2017, 01:03:09 PM »'s my peeuny contribution to this wonderful 900rr shock research you experts and gurus have been creating.
Here are some photos as best I could take without taking off the tank of the how the shock sits on the bike included with the reservoir incase you all were wondering where to stuff that thing.

1. it's a stock CBR900rr shock.
2. it contains a CB1 spring swapped out.
3. reservoir hose is stock therefore had to be mounted where it's shown on the photo. unless you take the battery out and set the reservoir in there but then you may not be able to have access to the dialability of the damping.
4. you can use "zip ties" or any other means to secure the remote reservoir - such as a cnc milled specific aluminum clamp but that'll cost you pesos.
5. I believe this location is spot on because a) it lets you keep the stock hose length and b) its accessible.
6. my weight is 200lb without gear.
7. height is 5'-9"
8. I believe it raised the rear end up by about 1/2 to 3/4" or so. Just bout right. I've also added a while back the longer sidestand. I think that too was from a 900rr I believe but I'll have to check my notes. that sidestand being longer helps with the added rear seat height.
9. the cbr900rr shock length eyelet to eyelet is about 1/4" to 3/8" or so longer than the CB1 rear shock.

I hope this has helped someone when doing their swap out.

« Last Edit: June 26, 2017, 09:38:15 AM by VintageHunter » Logged

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« Reply #1 on: June 26, 2017, 01:17:21 AM »

Nice pics and descriptive explanation VintageHunter. Thank you. How heavy are you? I've forgitten what you told me. How well does it work? Is it taller thsn the standard shock? Ive forgitten that too! :-)

It is possible to fabricate parts without a CNC machine. A double clamp that wraps around the frame, and another part that wraps around the reservoir could easily be fabricated by bending 1" wide stock stainless steel strips to shape using pieces of round bar, a vice, hand drill and a light hammer. A few layers of insulation tape would protect the paint on both items.

Your bike is very nice and clean bro. Mine has a million years of accumulated road dirt under the seat. I don't think it's been cleaned properly for a while. I'm wiping what I can see, but it seems as though you can only do it properly by removing components. And I'm not into jetwashing my bike. So the real cleaning will have to be done when I strip down and restore over winter.

Oh, has anyone else got a complete toolkit? Mine has, including the Alan keys and screwdriver. None show any wear. The blue plastic pouch is rather dirty and has a hole in it.
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« Reply #2 on: June 30, 2017, 05:56:19 PM »


I'm going to try and correct and error, but I have to explain a few things first.

I posted in another thread showing the the spring test data from the CB-1, CBR 900 and VTR1000.  The test data showed the CB-1 to have the stiffer spring (lower and upper rate) but due to the shorter compression stroke of each shock, you can see the CBR and VTR might get close to CB-1 top end capacity.

"Putting the each spring back into its respective shock" (mathmatically), you can see the differences the installation preloads make for each shock on the top end capacity. Over the max stroke of each shock, you can see the CB-1 is just eclipsed by the VTR spring.  Note:  each spring's curve is based on being on the 1st indent (installation preload only) on the spring.

Here was my error.  When I did the initial comparison to the CB-1 shock/spring to the CB-1 spring in the CBR shock, I noted the 1st indent to 1st indent was a 35% improvement (3,100 lbs vs 2,297 lbs)  This is a true fact, but its an incomplete observation.

Here is a more compete perspective - especially if you are a heavier rider.  As a heavier rider, you would have dialed in all of the preload (now on the 7th preload indent) of the CB-1 shock.  In this case, the spring capacity the oem spring can be set up to have a top end of 2,743 lbs.  When you compare this to the CB-1 spring in the CBR shock, the net increase is not as much, only 13%.  All this means is you have to adjust the modified shock like you would do for any other shock.  If you leave the hybrid shock on only the 1st indent, it will only have a 13% increase over the oem shock on 7th preload setting.  Add to this, the hybrid shock lower damping potential with the stiffer spring + the longer length, it can feel odd.

If you don't set up the hybrid shock right, this is the situation you might find yourself in.  First:  the hybrid shock is longer + it has a longer stroke.  This means it will push the swing arm down further than stock set up) for the start position (see green dot) and swing through to a spot past where the oem shock swings through.  The longer stroke (1.9") is depicted via the green line.  The oem stroke (1.53" is depicted by the blue line) is shorter.  The longer shock stroke means the rear suspension moves over a greater distance, 5.4" vs 4.3".  So, if you are a heavier rider (and bottomed out on the oem setup with the preload on the 7th indent) and you didn't set your preload on the hybrid shock correctly, you might still bottom out.  But instead of just bottoming out, it will feel weird because the rear suspension will be moving over a longer rear suspension distance combined with "different" feel since your rear is underdamped (to say nothing of how it is matched to the front suspension).

All is not lost, you just have to do the same kinds of things with the hybrid shock as you would do for any other shock.

1.  Set your sag amounts (adjust preload accordingly).  Because the installation preload is so great on this combination, you will not be able to measure the bike sag (try if you want), just set the rider sag.
2.  You need to make some damping adjustments.  I still stand by the rebound damping adjustment; just dial it all back in.  The CBR shock rebound damping was set up for a ~787 lb/in spring.  You now need to handle a 1,239 lb/in spring.  That means on the rebound stroke, the spring will be pushing with a lot more gusto than the oem CBR spring.  The rebound damping set up to slow that push for the oem CBR spring will not be enough for the CB-1 spring.  So, you have to increase the rebound damping and hope it is enough.  The compression damping, my initial thought was to dial it all in.  I think you should try something above the mid way point (it will be underdamped on compression), but with the stiffer spring, you should see how it feels and adjust from there.  If the damping is so weak, you may notice the rear going up and down 2 cycles to settle out.  

To help out, I will try this hybrid combination since I have the CB-1 spring + CBR shock.  I'll use the washer to track how things are going.  After riding on this for a while, I'll swap in a straight rate spring.  I have a 1,300 1,400, and 1,500 lb/in spring so making this change shouldn't be too big a deal.


Note:  I know some of the numbers in these graphs are a bit different from my other posting.  I did these at work and had to "remember" some numbers.  They are close enough to show the point I'm trying to make.  I'll clean them all up when I get on the main home computer.

UPDATE:  Adding a pic of my VH special.  I'll add a nylon washer tomorrow morning.  Note, I rotated the spring so I can get a good view of the washer.

« Last Edit: June 30, 2017, 11:59:41 PM by spacetiger » Logged
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