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Does bladder have to much pressure ?


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I just replenished the fluid in my shock and pressurized the bladder to ~ 150lbs. 

 

I was unable to move the shock shaft through its compression stroke, so I let a bit of pressure out and it was much easier to move. 

 

It now rebounds on it's own, i.e,. if I push the shock shaft through it's stroke it rebounds automatically. 

 

It does not have a whole lot of rebound pressure, but it rebounds back to its original extended position, is this OK, or should it not rebound at all ???

 

Thx !!!

 

Michael 

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I have the rebound at it's lightest point, or setting 1. 

 

It is off an old 87 XR200R, which only has 4 rebound and 4 compression adjustments. 

 

I just rebuilt one back in the summer and it did not have the same problem, but I took a different approach of putting in thicker ATF Fluid. 

 

I put Pro Circuit PCII fluid in this one to see how it would perform vs. Mobil 1 synthetic ATF. 

 

My goal was to try to dial in the rebound and the compression so I would have equal resistance.

 

I can do this via the pressure put on the bladder (compression side), however it is at the expense of having it automatically rebound. 

 

I thought I did a very good job of bleeding it of air as I spent 20 minutes getting out the air bubbles. 

 

I was curious if this was normal, it is very hard to get really good information on the Net for shocks. 

 

There is plenty of data on forks, but not so much on the shocks, at least what I could find.

 

Michael  

Edited by KTM520EXC
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It does not have a whole lot of rebound pressure, but it rebounds back to its original extended position, is this OK, or should it not rebound at all ???

 

when the piston rod is in the shock, the pressure forces it to extend, of course thats normal.

you must run at least 145psi, some XR Shocks use even higher pressures...

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My goal was to try to dial in the rebound and the compression so I would have equal resistance.

 

I can do this via the pressure put on the bladder (compression side), however it is at the expense of having it automatically rebound.

 

There is no reason that equal resistance in comp and rebound would be good or desirable, especially when you are moving the shock slowly by hand.  Resistance when moving the shock slowly by hard is not an indicator of how it will perform on the bike.

 

The pressure that you are varying does not exists to create resistance to compression.  It is there to reduce/eliminate cavitation.  Many old XRs (don't know about that model specifically) had crazy linkage ratios, and therefore need stiff valving and high nitrogen pressure.  You should set the pressure to whatever Honda recommends in the documentation for that bike, and you should NOT vary the pressure in order to change the way that the shock "feels" in your hand.

 

ATF is probably not a good choice for shocks, but that is a different discussion entirely.

Edited by Kyle Tarry
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"ATF is probably not a good choice for shocks."

 

Per "Honda factory manual specifications - ATF" and I believe that is what MX Tech uses in a lot of their applications. 

 

I have (2) XR200R play bikes, so I thought I would test both of them to see how each performs and at the same time teach myself how to service the shocks. 

 

Kawamaha and KyleTerry thanks for your input and yes the XR line does have some extraordinary ratio's. They generally come with 9.5Kg to 11.5Kg rear springs to compensate. 

 

Michael

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ATF will probably "work" in a shock. However, it is not as good as most shock fluids, for a variety of reasons. It is a higher viscosity, and a lower viscosity index, meaning it will create more damping than traditional shock fluids, and that the damping will have more variance with temperature than a proper shock fluid. It may also behave differently under conditions of high shear (such as smaller shim openings). Whether or not these things are of consequence to you, I cannot say.

I would be surprised if a high-performance company like MX-Tech advocated ATF in shocks for anything but the most basic of utilitarian rebuilds.

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