I’ve noticed that my Rockshox duel air 120-140 (I think)revelations are having a bit of trouble fully extending.

When they are fully extended they go out to the 130 mark on the stanchion, but I can pull out an extra 5mm without much effort. They used to go out to 135 without any problems. Is this them just bedding in, or the sign of something going wrong?

is that with you sat on the bike?? if so then i would call that “sag”

have you reset the pressures properly? do that first before worrying about anything else.
Just empty the neg, then the pos, then refill the pos and neg (in that order).

Also occasionalky service the air chamber, making sure there is a couple of ccs of fresh oil/float fluid in the air chamber to keep the o-rings sweet.

You’ve almost certainly got an imbalance of air pressures. Let th negative air out, then check and reset the positive air, and then the negative.

Dan – this is something that’s quite common with air forks, especially RockShox.

I think it’s clear that the problem is not related to sag as you’re saying you have to ‘pull’ them out, rather than they settle back to 140mm.

In the bottom of the fork is a nitrogen charged ‘negative spring’ chamber. This helps push the fork back to full travel after it’s been compressed. The negative spring can become flooded with damping oil at which point it will stop acting as a negative spring and the fork will sink into its travel by about 10mm.

You should be able to get this fixed under warranty, but it will need to go back to the distributor for the work to be done. If it’s not under warranty, then you can send it directly to TF Tuned.

In the bottom of the fork is a nitrogen charged ‘negative spring’ chamber. This helps push the fork back to full travel after it’s been compressed. The negative spring can become flooded with damping oil at which point it will stop acting as a negative spring and the fork will sink into its travel by about 10mm.

Erm, if they’re dual air then the negative spring is air filled using the valve at the bottom of the fork leg, I think you’re getting cofused with rear shocks which tend to have nitrogen charged chambers in them. What can happen is that the o-ring seal between positive and negative air leaks slightly and the fork sinks into its travel. As above, empty both chambers and re-set, if it happens again, try adding a couple of CC of thick fork oil or Red Rum etc to both chambers with a syringe after removing the valve core. If it’s still an issue, needs a new o-ring fitting.