[Closed] 150mm Revelations - being sucked down

I get this on mine and am a slightly heavier rider. Run them at about 115psi. Mine are the uturn versions and often often find after big hits they wind themselves down which is really annoying.

Did an uplift day at Cwm Carn a few few weeks ago and by time I reach the bottom of a run i found they had wound themselves right down to minimum travel which was annoying and made the bottom section very sketchy!

I reset the pressures every month or so and never really find they have lost most pressure. When I called TF Tuned a couple of weeks back they suggested the helix might be damaged in the left leg but this would be about £200 to fix and as my LBS replaced all the seals are serviced them two months ago I am reluctant to do this.

Already had one warrenty repair on these, so not keen to send them off again for a few weeks. I've had 2 sets of Pikes previously, one did this a little, the other not at all.

My u turn revs also suck down to about 135mm if I have equal -ve and +ve pressures but as with you the sag seems to be about right. I've not used them in anger since renewing all the seals, fluids and u turn/air tube assembly but am hoping that if they sag to the right height when in use it won't be an issue. I ended up having to do all the work after the left wiper seal popped out on their first outing after buying them from the classifieds on here. My air tube had some scuffing where the air piston sits and I assumed that was the cause of the lower leg being pressurised thus blowing the wiper seal. Jamie's problen does sound more like a u turn issue. The u turn helix assembly and air tube now come as a complete assembly and is about £75. I got mine from Simon at Loco.

Mmm, interesting. the question is whether or not there is a fault with my forks, if there is I ought to get them warrented. They feel OK riding, but it's easy to convince myself they are lacking a bit of travel at times.

The forks can get sucked down by just repeatedly topping up the chambers, although I would be surprised it being that much.

Try starting from scratch. Completely empty the -ve chamber, then set the +ve, then set the -ve

Now that's curious. Emptied the air from both chambers, cycled the forks, made sure both were empty, repeated several times. Then put 90psi in the + chamber and turned the bike upside down to inflate the - chamber. Shock pump read (-)30 psi.

Can air leak from one chamber to another? Seems like this could be my problem.

Have to say these forks have been pretty unreliable so far, not sure moving on from 454 Pikes was such a good idea....

agentdagnamit - Member
Now that's curious. Emptied the air from both chambers, cycled the forks, made sure both were empty, repeated several times. Then put 90psi in the + chamber and turned the bike upside down to inflate the - chamber. Shock pump read (-)30 psi.

Can air leak from one chamber to another? Seems like this could be my problem.

It can if there is a busted seal(s). Worst comes to worst, just replace the o-rings. Sure LoCo can sell you the right ones.

My 2011 revs came with very little oil in the air chambers, reckon they'd wear quickly like that (think they should have 1-2 cc in there, mine had just a tiny drop).

Won't the lower chamber be pressurised a bit simply from pressurising the upper chamber...

My 2010 air u-turns did that all the time, then they finally went bang! Both seals popped out and the fork collapsed down to zero travel. It could have been really nasty if I had been ploughing through a big load of spiky rocks but as it was I just about got away with it. Wasnt super impressed when it happened again 1.5 hours after they had been returned from Rockshox! To be fair they have now replaced them with new 2011 dual position airs which seem to be a lot better.

My 2010 rev rti ti 150 do exactly the same, empty both chambers + & - then fill the + to the desired pressure and fork is at the full 150mm then pump the negative to the same pressure and the forks creep down to approx 135 - 140mm. Had a lower leg service by Loco and Simmon said this is normal as the negative side is basically pulling down and the positive is pulling the forks up, but this seems odd to me as surly you are not getting the full 150mm of travel that these forks are meant to be.

My 2010 dual air's do the same. They also spit out fork oil when I release air from the neg chamber. I guess it comes from the few cc of oil in the +ve. Have tried changing the seal between +ve & -ve chamber, but still does it. Slightly annoying but have lived with it.

Could it be tolerance thing on the inside surface to the stanchion?

Oil spurting out of the negative valve is normal, but irritating (it'll contaminate your rotors, get in your shock pump and eventally reduce the amount of lube in the lowers, though that's easy to top up).

I dont buy the explanation from Loco in Sepdon's post above, as there is no "suck down" until I've ridden the bike for a couple of miles. This makes me think it's air migrating between the +ve and -ve chamber. Either because of a faulty seal (or in my case because the inners may have been damaged in a faulty circlip incident that Fishers sorted out).

Looks like mine are heading back again. I like the idea of the 2-step replacement option!

Just seen this thread while having lunch.

I think it may have been a different question that Shepdon's answer was for so not really applicable to your issue agentdagnamit.

If the forks are looseing travel over the course of a ride after the sag has been set it would be best to return for a warranty repair.

Any oil lost out of the negative chamber is from the air assembly in the upper leg and isn't reducing the volume of the damping fluid in the lower leg. When filling the negative chamber it's best to turn the bike upside down and let it sit for a minute or two which should reduce the amount of fluid lost.

Thanks Loco - I didnt realise that, but it does make sense when I think about it. Sorry for my bad advice!

So, what's the consequences of squirting out a little of the oil from the air assembly each time the -ve chambre is filled up (even if I turn the bike upside down, my Revs and Pikes have always fired out a little oil)?

Sorry to jump on the anti 2010 revelation bandwagon, but I just wondered if loco had any idea why my rev team dual air would have crap small bump sensitivity? Lovely and plush on big hits, but almost feel locked out on the smaller stuff. I've messed around with air pressures, but even running so much neg they start to pull down doesn't seem to make them any better. I miss my 2009 revs with motion control, I thought blackbox dampers where supposed to be the best!
The 2-step damper option sounds interesting? Is it a retrofit that's available?

Without wishing to cause panic, I've got a very similar issue with my Revelation U turns.

The first time I used them (on a fire road) they punched straight through the travel, breaking various seals and components internally. They were duly sent to Rockshox got refurbed and I've had them on my Zesty for about 6 weeks now.

For the past 2 weeks or so they've been sucking the travel down, no matter what I try pressure wise in the +ve and -ve chambers. Not sure if it's a problem or not but as the OP says it's difficult to tell yourself you're not losing travel.

Anyway I've just had to cut a ride short as the u-turn mechanism is now FUBAR. Within a couple of minutes of riding downhill the travel is reducing and I need to turn the uturn knob to restore the full travel and repeat until I get back.

Incredibly frustrating to get a set of forks which had a known issue but no recall, have them warrantied only for them them break less than 2 months later. To cap it all I bought the forks in Dorset and I'm in France so I've got the whole warrenty issue of only being able to deal with Rockshox via the dealer. If I have a problem with a snowboard the manufacturer deals with it no matter where I bought it from. Gah.

I had this prob with my reba's but the forks were due a service so i replaced all the seals with a set of ebay and this cured the prob but it came back after 2-3 months and seems to me that its due to not enough oil covering the air seal in +ve so i've started putting 10 ml of oil instead of the recomended 5-6ml and this seems to have done the trick for me,no probs for 3 months now...

Meribelmtb - that sounds familiar. Fisher's blamed it on a dodgy circlip. I was hoping for a new set of forks under warranty, but they assured me they had successfully repair the fault. I was worried that other parts had been damaged, or the inners scored, turns out that might well be what actually happened.

Pretty shoddy. Not sure whether to cut my losses and buy some Dual Position new Revs, or persevere with these?

Have just got an email back from the LBS that I bought forks from. Fishers reckon that there might be a problem with the bearings that spin the uturn dial. Going to have a look at them tomorrow and will report back.

Quick update. Turns out that the bearing had slipped off the springs and dropped into the holes below the dial. This meant there was no pressure against the dial and nothing to stop the travel dialing down. Looks like it's fixed for now....

Thanks.

My problem may be fixed for now, simply by thoroughly removing all the air from both chambers and starting again. Feels a bit harsh on small stuff though, so reckon I need more -ve pressure (which will probably result in a loss of travel again).

Anyone want to buy some iffy 2010 Rev's so I can get some Dual Position 2011s?!

I found that my 2010 Revelations U Turns are very sensitive to pressure adjustment. I believe that the volume in the - chamber is significantly smaller than the + chamber and when you disconnect the pressure gauge you loose much more pressure from the - than the +. Just check your readings + and - once you have taken the pump off and put it back again. You will see that - has lost lots more pressure than +.
I always wind them all the way out to 150mm, wind off all the rebound damping and set the sag with the + chamber. I then start pumping the - chamber up until it starts to suck the travel down. At that point I release tiny amounts of air from the - until they start to rise again. I'm not saying this is the solution for all but it works for me and they don't suck down on a ride.
I also find that the pressures shown on the legs and in the manual are too high for my weight and run them about 20% less.

I believe that the volume in the - chamber is significantly smaller than the + chamber

and when you disconnect the pressure gauge you loose much more pressure from the - than the +.

You don't lose pressure when you disconnect the pump, only when you re-connect it and air travels from the chamber into the pump.

😀 2 nights ago when disconnecting the pump on mine the valve in the fork stuck open & let loads out. Shouldn't happen of course.