Hello all

I have a question for anyone who has any experience with a 140mm rockshox revelation fork or more accurately a stumpjumper 29er with the above.
After i purchased the bike I went through setting up the suspension in the same way I set up my previous bike (specialized camber) rear shock is simple due to the idiot proof autosag, then the forks.
Until a couple of days ago I thought this was also straight forward, as a start point read the rider weight/air pressure chart on fork and pumped in the air. I sat on the bike and there was no sag in the forks at all I then took my bike onto the road, the fork worked like they were filled with way too much air. I checked and air pressure was OK, so I reduced air pressure until the forks settled to around 25% sag when I was seated, but as soon as I got out of the seat and put any weight over the bars the forks dived through the travel. Anyway I decided to take the bike out and do a local ride, somewhere I’m familiar with. I did this and played around with the pressures until I was using around 85-90% of the travel. On the trail the forks feel absolutely fine but when travelling along in a normal pedaling position there is little or no small bump sensitivity, they feel really harsh and if I hit the brakes the forks dive quite badly. Is this normal or do the forks need a service? The bike is 2015 model so I wouldn’t expect the forks to need a service.
Any thoughts???

Sounds like they don’t have enough slippery slidy bath oil.

I would open them up and see what is in them.

I have the same problem with my pikes at the moment, and suspect that is the problem.

I often feel that Rockshox forks need a service before they get ridden sadly, but after that are pretty fit and forget.

Are they solo air?

Sounds like the negative spring might not be filling up, but would need a feel of them to know for sure. What you’ve described is quite a classic symptom of that as no negative air means they sit at full travel even with the right air pressure inside.

Basically there’s a little cutout inside the fork that allows air past the master piston to fill the negative side. It can be blocked with grease or bits of oring or sometimes the piston doesn’t sit in the right place.

Well I’ve had a few bikes and never a set of forks that feel so bad. So you guys agree that they are definitely not as they should be?
Going from a 110mm xc style bike to a 140mm trail bike I didn’t expect the trail bike to be a harsher ride of the two.
Maybe a full service is on the cards but it’s really annoying to say the least.
Thanks lads

Sounds like exactly the problem i’ve been having.

i will investigate tomorrow. Also come off 100m forks which felt better.

I’d appreciate if you could share any useful info from your investigation Joe. Who do you guys recommend for a fork service? I’m thinking of maybe using tftuned.
Cheers

Sounds like the negative spring might not be filling up, but would need a feel of them to know for sure. What you’ve described is quite a classic symptom of that as no negative air means they sit at full travel even with the right air pressure inside.

This. Going through the same problem with my solo air Reba forks. Been back under warranty once already but they keep doing it.

What has temporarily worked for me is to bleed/burp the lowers by releasing all the air, compressing the fork and gently sliding a zip tie between the stanchions and seals.

The forks feel great again for a good few rides but then they’re back to sticking again. Similar symptoms, no small bump sensitivity, works better on bigger hits etc.

I’ve read that the negative air chamber problem can be caused by too much grease which blocks the port between the positive and negative chambers.

Much preferred the old dual air forks.

I got a guy at sram to look at my forks today and he confirmed that they weren’t working as they should, he dropped air pressure to zero and the forks still wanted to spring back up. He said it’s probably caused by blockage of a port which should open and close to stabilise the positive and negative air Chambers. Any way with as little as 50psi the forks were still really harsh. Looks like a service

I’m going to service mine tomorrow and will let you guys know the result.

Not having much luck with this forum this evening…but anyway…

Took my pikes to pieces, this evening. Very easy job for any half competent home mechanic. Slid lowers off in about 2 minutes.

The circlip on the air chamber is a little bit of a bitch, but it popped off eventually.

The valve or notch which people mention is on the inside of the air chambers stanchions. I took this photo looking down from the crown and have circled it in red for anyone who is interested. There was way too much assembly grease on the air seals. There was nothing obviously in the notch, but i ran a dry clean rag up the stanchion anyway.

[url=https://flic.kr/p/rdjp7N]IMG_3360 copy[/url] by joesheffer, on Flickr

Reassembled with lots of oil on the foam dampers (they were very dry and these forks aren’t that old!) and then added the correct amount of lube into the lowers. (I suspect that this had been on the mean side from factory).

Anyway…once i did this the forks still felt like there was trapped air somewhere in the negative chamber (i hadn’t repumped the positive chamber yet)…so I ran a ziptie down both sides of the seals and out came little farts…and for the first time the forks sat at nearly no travel while empty of air.

To be honest I think this whole negative air thing is a pile of shit. Give me back my Fox Floats from the mid 2000’s…best forks I ever had…serviced them in 10 minutes every couple of weeks and no hassles.

Don’t touch the compression damping.

Forks now are buttery smooth and plush. Bit of a pain in the arse…but anyway.

Nice info Joe, thanks. I’m going to have a go at taking my Rebas to bits when I get a spare weekend because I’m still having similar problems with them.