The Revelation air fork on my 2011 Stumpjumper has developed a fault. The lower air chamber can no longer hold any pressure. (The valve is NOT leaking.)
When pumped up to 80 lbs pressure it drops quickly to zero on pumping the legs up and down. The upper air chamber is unaffected and holds its pressure, and the oil damping on rebound works fine.
For all the difference there seems to be in riding with zero pressure in the lower chamber, what is the lower air chamber supposed to control? Is it the upper air chamber which 'holds the forks up' and prevents them from just collapsing, or are ther springs inside the legs?
At anyrate, is there any logical reason not to go on riding them, since I can't discern much difference, if indeed there IS any? Is there a safety issue, and if so WHAT?
Probably just a worn o-ring inside, maybe there wasn't enough oil in there to lubricate it.
The negative spring basically balances the fork at the top of its travel. Without it, you might get top-out clunking and a harsh ride (or if you let air out of the positive to make it soft enough at the start, it can be too soft at the end). It's a bit like running a coil shock with loads of preload.
I don't think it'd be a safety issue really, but email LoCo i'm sure he'll know exactly which o-ring you'll need to replace.
Mine started doing the same thing. Then the pressure started to seep into the upper chamber after i put quite a bit of air in. That made the fork feel rigid. Anyway, Loco has them now for a service.
Mine did feel bad, the fork dived through the travel when the lower chamber didn't have much pressure.
Thank you for the replies. It now seems to be improving, and holding more pressure. starting from 80, it now drops to 40 ater a good session, and may (hopefully) re seal itself.
Thankfully, the air has never leaked into the upper chamber, so a glitch in the O ring sealing may have been the problem. Thanks again.