Lost small bump compliance on my forks.

jairaj

I've got a set of RS Revs, recently they have lost small bump compliance and my usual air pressure is giving me only 5-10% sag where as it used to give 25%. Large bump compliance seems OK.

I've owned them since 2010 years so they don't need bedding in and I got them serviced last year.

Is this just a simple case of the forks needing a lower leg service? Which from reading the various guides on the web looks simple enough to do.

Or could there be something else wrong? Are some simple tests I should perform to check?

I only ask as previously I had them for about 2 years and they felt fine without servicing until one day a seal let go and popped and I sent them off to get fixed. Its about a year since I got them serviced and I've done hardly any riding on them ~3 months of just riding weekends as I was injured the whole of summer and autumn.

thanks Jai

supersonic

Check the negative air chamber - might have lost pressure. Set sag again basically.

bennett_346

After a year i'd give them a service again anyway. But i agree with the above. On my RS Revs a loss of even a tiny bit of pressure in the neg chamber makes them rattly on small bumps and chattery things. It's such small volume that even a 1psi drops causes a difference in feel.

jairaj

@ Supersonic:
Yeah already tried setting the sag again (many times). removed all air from +ve then -ve. Pumped +ve to 100psi then pumped -ve to 110psi which is my normal setting. I weight ~95kg with riding kit on.

I'm having to put about half my normal air pressure to get any sensible sag (50 in +ve and 60 in -ve) Haven't tried the forks on trails like this. But as said big bump compliance was OK at 100psi.

The compression circuit should be fully open. Its a poplock motion control unit without the lever removed so the internal spring should keep it fully open.

@ bennett_346
Its been ~1 year since servicing but I;ve only ridden it for 3/4 months and only at weekends. Where as before I try and get in a few shorts ride mid week.



I guess I have I just been unlucky and dirt has worked its way into the forks quicker than normal? Or is there anything else I should check?

bennett_346

jairaj wrote:

I guess I have I just been unlucky and dirt has worked its way into the forks quicker than normal? Or is there anything else I should check?

Unlikely to be the case imo.

camerauk

This is very strange I am having that same problem on my Reba shock
I was wandering if it is the cold weather doing it

bennett_346

Very cold air can thicken the oil.

camerauk

I have been having this problem for about a month now, I have had to drop the pressures to around 75psi in both + and -
I normally run about 100 + and 110-
I was going to give TFTuned a call and see what they have to say

bennett_346

I'd keep 100 + but add more air to the negative rather than drop both. That looks like too much to have to drop for it to be caused by thickened oil.

camerauk

bennett_346 wrote:

I'd keep 100 + but add more air to the negative rather than drop both. That looks like too much to have to drop for it to be caused by thickened oil.

If I keep 100 in the + I hardly have any sag so the fork feels way to stiff
I have tried adding extra to the - but it made little difference to the way the fork felt it did make it smoother but with the small amount of sag I was only using half of the travel
I did remove all the air from both chambers and the forks compressed all the way down and felt nice and smooth

camerauk

Was nothing to do with the cold air in the end.
I took the plunge and stripped them down cleaned out lower legs and removed oil from the top of motion control leg
fitted new foam seals and wipers, new oil in lowers and refilled Motion control leg and they are feeling lovely and smooth again with the pressure back to what it used to be

jairaj

Good to hear that worked for you.

I did a lower leg service on Monday got to the very end only to realise I had damaged a washer so waiting for a new washer before I fit the forks to the bike and give them a try.

The old oil and foam wipers in the forks were very dirty. Hoping new clean parts and fresh oil will fix my issues too.

camerauk

Yep sure it will my oil was not to bad but the foam rings were dirty and dryish