Am experiencing a loss of travel on my 2009 RS Revelation U-turns and can;t figure out why it is happening. Thought it might be air set up but no – I completely emptied + and -ve air chambers but still cannot get the fork to compress to full length of travel – it stops about 4cm from crown. Removed and cleaned lowers / seals and all looks fine and re-filled with 15ml of oil as required in each leg. Still happening. Any ideas?

When you removed the lowers did you try and compress each leg seperately?

that might reveal whether its a fault with the air spring or the damper side.

I didnt try compressing the fork with the lowers removed – was not sure this would be ok to do TBH. Not v. confident with fork servicing. Just cleaned all and replaced oil etc.

Hmm sounded like hydraulic lock in the right hand damper leg, it's common for oil in the damper cartridge to leak into the lowers. As it's not compressible you lose travel (and lock out as well). If you took the lowers off though this oil should have drained out (would still have left you with a lack of damping though). Need to do what horatio suggested, try putting pressure into the negative chmaber and not the positive. This should suck the forks down fully.

Cheers – just to be clear – its a loss of travel I'm getting at the top of the stroke, not the bottom. The fork seems to be "sucking" down to the full 140mm travel mark ok. The lockout is working fine also.

So do I need to remove the lowers again and then put air into the -ve chamber to suck the fork down ? , or do I do this without disaseembling the fork? Not too sure how to proceed.

Ok, you've got me confused now. When full extended you've got 100mm of stanchion showing? Try emtying the negative air chamber (schrader valve on the bottom of the left hand leg), this should return them to full height. Sounds like too much air in the negative spring, this will reduce available travel. If this works fill both poitive and negative chambers with the same air pressure. this should give you roughly full travel. I personally run my REBAs with slightly more in the negative chamber to make the forks more small bump sensitive but that's rider choice.

if on the other hand with no air in the positive spring (shrader valve on the top of the left leg) you still have 40mm of stanchion showing it's pointing to hydraulic lock or busted internals.

if all that fails I'd recommend a full service and change all the O rings, if you're not happy doing that yourslef send them to TFTuned. It' cost but at least you know they will be working properly when you get them back and their customer service is excellent.

Sounds like a hydraulic lock due to seal blowing in the bottom of the leg,
drop me a mail for parts or a service if you need anything.

Simon

na – the problem is when the fork is being compressed. cI run them with 5psi LESS in the -ve than +ve chambers and can wind out the U-turn to the full 140mm marker no bother. what happensd is that no matter how big a hit or forced compression you make on the forks , the lowers are stopping short of the fork crown by a good 4cm – i.e nowhere near bottoming out and so when you are riding the actual amount of travel available is 4cm shorter than you think you have. Maybe this is normal but i dont think so, andn it is not the same on my Fox forks. This still occurs even when both + and -ve chambers are fully emptied and the fork compressed hard, so its not looking like it can be anything to do with an imbalance between chamer pressures. Its not a big problem as this kind of bit hit on the forks rarely occurs but it doesnt seem right. Perhaps they are **** and need to go to see Tim about it?

That's kind of what I meant, if the oil in the damper leaks into the lower leg if the seal has gone, the extra oil in the lower leg of the fork will only it to compress so far due to the hydraulic lock.

There is too much oil in the damper side cartridge.

sorry Simon – I replied to Stumpyjon before I had received your reply. Will email you. Cheers
C

No problem, wasn't quite sure I'd explained it clearly enough. 😀

nicolaisam – Member

There is too much oil in the damper side cartridge.

+1
just done this on a mates revs his had 170ml instead of 140ml
would only get 100mm of travel at best all better now

My Gf has this issue on her non uturn revs. She rode round dalby yesterday on her 6" fs with only 100mm of travel on the front.

Should I send off to TFT or do it myself? Also where is best to get he parts from to service and rectify this issue?

Get the parts from your LBS or order direct from TFTuned. The two kits to do a full service though cost around £ 40 and come with quite a few parts you don't need. The service itself is relatively straight foward using the guides on SRAMs site.

These are the seal kits you need for the a full service:

11.4015.263.000 U Turn air service kit RRP £24.99
11.4015.250.000 Damper service kit RRP £16.99
and either
11.4308.850.000 Separate oil and dust seals and foam ring RRP £22.99
or
11.4310.290.000 Combined oil and dust seal and foam ring RRP £13.99

Hope this helps.