BASTOK

Hi all !

I want to change the original rear shock of my '99 XX. Here in my country putting a Olhins it's almost impossible, we are talking about U$S 2000 o maybe more.

I will buy something used but in good shape in the US, but I need to know if someone knows which models of rear shock could easily fit the XX (the 99 or upper).

Here I know someone adapt a cbr 600rr 04 and it works fine. But was on the XX '98, carbs, so there are differences in the space available to put the new one, especially the gas bottle.

Did someone have some experience on this ??


Thanks in advance!

Bastok

Nutter67

Another alternative is to fit the rear shock from a pre '95 CBR900RR. Just needs a heavier spring (and a rebuild/overhaul). It will bolt straight in - just need to find somewhere to mount the remote reservoir. I upgraded to a longer braided line and fitted the res under the seat.

__________________
Paul

Never let a motorcycle take you somewhere your brain didn't get to three seconds earlier

CanadianBird

You could ship your shock to Jaws during the "off season" for a rebuild. You could try Penske, maybe it's more affordable than Ohilins. The above advice is probly better.

smurf211

Here are some notes:

Penske Shock Installation problems....

CanadianBird

I remember that tread and I bought my Penske from Tripledigets. Is he still on the board? I had my tech do the install it's mounted near the left side grab rail. Bike can still go on the centre stand and now the rear wheel is closer to the ground. I confess I do throw a lot of dosh at my bike parts and labour, and I'm able to. I recognize others are very skillfull and prefer and are able to do their own work. My hat's always off to them. I also am aware not everyone has "unlimited cash" to throw at their Bird. Which is why this forum is so excellent. Advice, alternatives, pictures(except me) abound. The skill level is very high on our forum. Good luck on you search for a new rear shock. Of course then you'll have to re-build the front. lol

BASTOK

Thanks you all for the quick answers.

I will look if I find some 900rr on ebay in good shape, because I think the 900rr '95 we could find maybe there are quite old and no in 90-100% working condition!

Living in a country where you have to pay 100% of duty taxes to import things from other countries is dissgusting. If you tell me a Penske for U$S 600 or an Olhins for U$S 1000, well maybe I'll think of it, but U$S 2000- 2200...........

I think something used and in good shape for the rear ando maybe some Hyperpro for the front (new) I'll be wasting near U$S 700-800 and improving the front and the rear ...

I will continue in touch!

Banshee

I got a cheap 900rr, then had it rebuilt, revalved with Gold Valves and a new spring to suit my weight & riding style. Made a fantastic difference.

On my last BB, I just had the OEM rebuilt with Gold Valves and that alone was a fantastic change.

As long as you don't need to be adjusting the rear a rebuilt OEM BB rear is fine. If you need to make adjustments for 2 up/single or road/track days, then an overhauled 900rr or aftermarket would be preferable.

lois

Questions.

Was that a pre 95 like Nutter stated?


What make of shock is it?

Lois > aka, man of many questions.

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Call me "Captain Mudbucket".

Banshee

Yes, it is a '94 900RR. That's one of the main reasons I went with full rebuild.

Brand is Showa, same as the stock BB rear.

Mykl > aka, man of as many answers as I have. And a few extra questions, as well...

lois

Thanks guys.....I will try and locate one.


Lois

__________________
Call me "Captain Mudbucket".

shewie

There is something brewing on this topic. Stay tuned for another of smurf211's excellent write-ups. BTW, you may want to hold off on that, Lou, unless your Gixxer is boring you and you want to take your bird to the track.

__________________
If you don't like the way I ride then stay off the sidewalk.

smurf211

So far from all the research I have been doing this recommendation is dead on. I talked to John at Jaws and the economical way to go is the BB stock rebuild with a heavier spring and look into the possibility of having it converted to oil over oil instead of gas over oil, which is optional. But if you want the adjust ability as stated above, the 900rr is the way to go. The heaviest spring for the stock 900 is 15kg/mm. Race tech calculator for me is 17kg/mm. which isn't far off. Motion-Pro has a spring for about a $130 that is a lighter mm rate but progressive (PDS). I also found some ballpark numbers to get an idea of cost: $150 rebuild, $50 re-valve, ~$100 re-spring, total about $300. I just won a bid on eBay for a '93 for $40. So for approx 350 +- plus the extension for the reservoir, we are at about half of what a Penske would be and about a 3rd of an Ohlins. Again this is all personal pref. I think with reasonable effort and cost you can upgrade and then adapt to your components and learn their limitations. The best bang for the buck for the front, according to John, is the kit they have with the longer springs, shorter spacers and 10w oil. Apparently they have put a lot of time into evaluating this and they feel the gold valves and the golden (price) shocks are marketing hype and ridiculously expensive. To some extent I have to agree. Again, this is up to the individual and is subject to personal preference, and what your requirements are. You can always upgrade in stages. I did a part number comparison if anyone wants to see it from Ron Ayers and the 900rr shock list the same number all the way through 93 - 97, but when you start spec-ing out the 900 shock on Race techs page they list from 92-94 in a group. I won't post all that but I think it is safe to stay with a 93 or 94 year shock.


Here's a link. There are plenty of others. I tried to look at Eibach and all I could manage was dirt bikes. I must be missing a link on the page.

Moto-Pro Suspension


I am going forward with my RT Gold valves for compression, rebound, and the springs. I am getting a clunking sound when I go over the railroad tracks by the house. My confidence factor is limited right now. When I had the Triumph and the Pilot Powers I would not hesitate to lean over, but I'm just not there yet with this machine. I feel my tires are adequate, and the shock will do for know, but my front end is suspect so I haven't gotten to frisky with it in the corners. Hopefully we're going to change that next week. I am also putting a 47t on the rear, total error correction for that is -11.75% on the SH. ... // smurf

Banshee

Damn, the post I wrote earlier didn't stick. Have to type it again.

Ok, I have an Eibach spring from this page Eibach Springs - Performance Suspension, Lowering Springs, Shocks, Sway Bars, Coil-Overs and Wheel Spacers!

I selected motorsports, then used the application selector link. Then North Am, Coil Over, Main, Imperial, 2.25, 6.0. The one used for my rear was the 0600.225.0950. Whish is 6" length, 2.25" ID, and 950 not sure of the units, lbs/ft? Don't remember. That is for a rider ~85kg (~187lb) on the bike with bag for street, not track, riding. They also put in a spacer ~ 5-10mm thick as the spring is shorter than the OEM Showa one.

smurf211

Ok, not having the specs from you I would have NEVER found this. Is it safe to "assume" that the 950 designation is kg/mm?


And haven't some of the heavier riders been going with the 1100 kg spring rate?

I'll add this to my info collection. I should probably summarize and place this over in my suspension tracking thread. Thanks, Banshee. Also 1 kg Racetech fork springs are not to be found so I ordered the .95 kg for the front. I believe X1 has these and if it's good enough for him it will certainly do for me. // sm

Eibach Springs - Performance Suspension, Lowering Springs, Shocks, Sway Bars, Coil-Overs and Wheel Spacers!

Attached Images

Eibach Spring rate.jpg (25.7 KB, 19 views)

Banshee

I think you may be correct with that, smurf. Although 950 kg/mm would sound more like a bar than a spring! kg/cm perhaps?

I used the calculator on the Racetech site to work out what spring weight would suit me and then picked the closest from Eibach. RACE TECH PRODUCT SEARCH

For 75kg rider (no gear), I get ~16.6kg/mm = 923lb/in. So it is lb/in after all and the heavier guys are using an 1100lb/in spring.

smurf211

This is what I've come up with. My question next is adapting the heavier spring to the 900rr shock. When I get the 900 shock in I'll supply some photographs for comparison. It's kg/mm but a beer sounds great right about now.

Attached Images

racetech 250 # on a blackbird.JPG (71.6 KB, 19 views)

shewie

I'm so glad that you are doing all this, smurf. After our conversation I think I will do some fiddling with what I have, but I need to pick your brain some more and find out what else you learned about rebuilding the Showa unit.

__________________
If you don't like the way I ride then stay off the sidewalk.

Banshee

When I had mine done, I took it to a bike suspension specialist. The drilled the unit to release the pressure, (there wasn't any, surprise, surprise), then stripped it down and cleaned it. When it was reassembled they put in a valve to repressurise it. (At least, that was what they needed to do for the OEM BB shock, I don't remember if they needed to do that for the 900RR, but I think so.)

Once stripped & cleaned, they replaced the OEM valve with a Gold Valve & shimmed to suit my weight. The made up a spacer to go on the end of the spring as the Eibach spring is shorter than the OEM 900RR spring (~1/4"-1/2") and is not tapered like the OEM. The also made a spacer which was fitted on the shaft of the shock internally that effectively lengthened the shaft so it doesn't need the 6mm shim on top. Refilled with fresh oil, assembled with a longer hose between shock & reservoir, (from memory they used a leftover Galfer SS braided brake line they had from when they sold them as well), & repressurised. A bit of fine tuning of the settings with a ride test or 2 & it was all good.

edit: Added a pic of the stock valve from the 900RR shock.

Attached Images

shockvalve1b.jpg (129.4 KB, 27 views)

shewie

Banshee, would you mind laying out exactly what you had done to the stock unit? I think I will keep using mine and just try to make it as good as it can be, so any info I can gather will be helpfull come winter.

__________________
If you don't like the way I ride then stay off the sidewalk.

Banshee

On my '98 I had the OEM BB unit overhauled by a bike suspension specialist.

They drilled top of shock to let out pressure & disassembled shock. It was cleaned out & the valve removed. Gold valve was installed & shimmed for my weight & road bias (as against track bias shimming). As I very rarely ride 2up or track, a set & forget system was fine by me then.

They then reassembled it with fresh oil & original spring, as it was in the right range for my weight at that time. The put a schraeder valve in where they drilled the top of the shock & repressurised it with nitrogen. Put it on the bike with a 6mm shim.

I then took it out for a ride & they tweaked the preload & rebound based on what I told them. Practical upshot is that the ride is much smoother. If you look at the pic of the valve I put in the last post, it is similar to the BB valve, although that had fewer larger holes, they still aren't all that large. The Gold valve, however, ony has 3 holes each for compression & rebound, but the take up most of the face of the valve. Probably more hole than valve! As a result, when you hit a small sharp bump, the size of the holes in the OEM valve restrict the oil flow, so more of the inital impulse is transmitted to the frame. With the much larger holes in the Gold valve, more of the oil is allowedto flow through the holes with the shims doing the control of the response to that same inital shock. So the force transmitted to the frame is smaller, but over a longer time, smothing it out better.

In the pic, you can also see the OEM rebound valves. I had these done with the front on both my '98 & '07. It seems that for most road riding the OEM compression valves are fine with lighter oil (5wt). They replaced the rebound valves & shimmed as appropriate for me & used slightly heavier Racetech springs which, like Jaws spriings, are ~100mm longer with a shorter spacer. The Gold rebound valves also had much larger holes than the OEMs. Again, this lets the shim stack do the work of controlling the oil flow rather than the valve holes. Having said that, I suspect that the main improvement is from the springs & lighter oil. The lighter oil having the same effect as larger holes, by flowing through the compression valve easier, and it is the reduction of the inital impulse when you hit the small bumps that takes much of the harshness out of the ride. The springs then give you the better ride & cornering feel. It is usually said that the front, in particular, is overdamped & undersprung, which is why the basic conversion of Jaws springs & lighter oil works so well & is such good value for money. Once you go far beyond that, it becomes a matter of diminishing returns. Although some want that extra adjustability & use it, for most of us it is more likely that a single set & forget is the best value option.

Are you confused yet? I think I am!

shewie

Okay, thanks Banshee. I wonder if the stock valve could be drilled to mimic the Gold valve. I think I need to do a lot more research on this. First thing should be to find a local suspension expert who can explain the shimming to me.

__________________
If you don't like the way I ride then stay off the sidewalk.

Banshee

What happens, is that there is a hole through the valve that is sealed off by the shim stack. This is a sort of conical stack of thin shims. When you hit a bump, the oil tries to flow through the hole, but the shims are closing it off. So the oil has to bend the shims out of the way to get past. The exact number, thickness and diameter of the shims used in the stack set how much it can be flexed initially and how far it will flex with continuous pressure, ie fast & slow damping response.

I would guess that a 'flatter' cone of shims would let it have softer damping & a steeper one would give harder damping as it would take more pressure to produce the same deflection in the shims.

I can see what I am trying to say in my head, putting it into words is not easy, however.

While you could drill the stock valve, I don't think it would be practical, as you would need to find the right shim stack by trial & error. Very costly in time & dis/assembly, I would think.

shewie

Hmm. I think I understand what you're saying. I would have to have it in front of me to really get it. You say the stack is conical? So the shims are of progressivley smaller diameter as they get nearer the rod? I'm off to try to find some shock diagrams and see if I can get on the same page as you.

__________________
If you don't like the way I ride then stay off the sidewalk.

Banshee

That's right. Widest at the valve, getting progressively smaller in diameter as they are stacked. There may be several the same size, depending on the response you want from them. In the pic of the valve, the shims are those discs held on by the zip tie through the middle of the valve. Not a good picture of them, though, I was aiming to show the holes in the valve there.

If you look carefully, you can see some of the smaller ones from the bottom stack half hidden by the valve & top shims. The ones on the top are rebound shims for the 4 small rebound holes.

smurf211

Banshee, John was saying something about converting the stock shock to oil over oil vs gas over oil. We were long distance and he was involved with something so we didn't have time to pursue. I guess I can call him back and discuss that issue solely. Have any idea where he was going with this?

Great write up, the further we progress here the better. When I get the 900 shock in I'll take some shots of it next to another BB shock I have.My original plan was to send the second shock t0 John and have him rework / re-spring it. This was last winter. He told me not to worry about it until I hit the 15- 20k mark. He did advise that the setting should be 1/4 inch of thread showing and a half turn back from max on the rebound.

Banshee

Not sure exactly what he means by oil over oil, but I do know about the gas over oil.

Working from memory, so some details may be a little off.

Basically, inside the shock, you have the oil that acts as the damping medium. In the OEM BB there is no reservoir, so you have a fixed volume. Until you compress the shock, that is. Once you compress it, the shaft is also inside so you have less volume for the oil. So you need to have gas in there for compressibility. Then you have the issue, that you need to keep the gas & oil separate to prevent bubbles messing with your viscosity.

So at the top of the shock is a sealed chamber, (in the 900rr shock, this is in the remote res), that contains the pressurised gas. The end of this can move. During assembly, the movable cap is pushed in, oil filled in the main chamber then the valve goes in on the shaft. Oil topped up & the sealing caps go on so there is no air or gas in the chamber with the valve. Then the shock is turned over & the top chamber filled with pressurised nitrogen.

This is a fairly high pressure as the gas will act as an additional spring in effect. If for example the shock caused a 10psi increase in pressure & the chamber was at 10psi to start with, that would be a 100% increase in pressure giving a substantial change in the 'spring rate' of the gas. BUT, if the same chamber had 100psi to start with, it would stil only have a 10psi increase to 110psi, so now it is only a 10% increase in 'spring rate'.

In the 900rr shock, the oil fills the body of the shock & the line to the res. There is a one way valve on the res to adjust a secondary oil path for more or less compression damping. This valve is bypassed on the rebound route. There is another valve to adjust flow on the rebound route. On the OEM BB shock, there is only the rebound adjuster. It is effectively an extra hole through the valve which alows oil flow on the rebound stroke. The adjustment screw allows you to vary the aperture of the 'hole' by screwing a pin in/out.

So says the guy who knows enough to understand what the experts are talking about, and what NOT to touch!

smurf211

So the difference between the front and the rear is pressurization due to increased weight and workload? Nitrogen for heat and gas stability. Not adjustable in terms of gas but adjustable in terms of fluid flow, although some are. Another thing, how do the techs know how to stack the shims and in what order? I understand the conical concept, I guess there is a basic design and the shims are added , subtracted, stacked according to weight and desired damping. Just looking to gain a better understanding, this level of detail is new to me.

I took a look at Traxxion dynamics. Although expensive, I realized one of their key selling points in the ability to remove their cartridges and re-install the old components if you sell your bike. This will allow you to move the cartridges to a new compatible system, probably with a little fine tuning (read as repeat business). Essentially they are providing a cartridge insert that has the springs, comp and reb setup up per your spec with pre load adjusters as an add on. Last time I checked they were about $1100. (with out the preload option). fwiw, -sm

Banshee

I believe the use of nitrogen is simply that it is cheap & dry. After all air is 70% nitrogen.

As to how the tech knows, Racetech supply a list of stack specs for each bike & rider weights. If you need a change after that (for fine tuning on track etc), then the tech need to know how to adjust it.

smurf211

I posted this in the wrong thread. Here's the link, sorry for the rant.....

Suspension for dummies:

BackStreet

I just put a progressive spring on mine and the stock shock is fine IMO.

If some other available shock is too short why not just make a longer bracket for the top mount?