I got a used rt3 yesterday to replace an ario shock. I fitted it yesterday , pumped it up to 250psi (14.5 stone) sag around 10-15%. Once sat on bike again i cycled the suspension up and down for a bit, rechecked the sag again and it changed to 25-30%??. So i put my pump on and the pressure read 225psi. Do i have a likely problem here?

Not necessarily. Shocks have such a small volume of air that when you attach the pump a significant percentage is used to fill the hose. Did you cycle the suspension before you set the sag? Part of it could simply have been sticky seals which you have since freed up when you bounced the bike. Reset and try again, basing your test on sag rather than pressure.

That was your positive and negative chambers equalising, nothing to worry about.

As above, but Monarch air can seals seem to need changing quite often. If it is this, they are only £15 for the kit and simple to do with the SRAM manual and videos.

Thanks for the info. After adding air it is stiff when i pop the saddle up and down but after cycling the shock a bit it goes what feels as soft . Certainly softer than the ario it replaces. The tune if relevant is M/H1.

On 265psi now and after working the shock up n down i still get a 25-30% sag on all lever positions. Surely that high it should at least be less sag than that?.

Air cans on those need regular servcing, so maybe air seals need replacing, if the damping i inconsistent as well it’s probably time for a full service.

By damping do you mean the min med max lever?. If so thats fine and the differences between each setting are noticable.

Just to add ….i went to cannock yesterday had 260psi i shock still the same 30% sag !!??. Rode three loops switching the lever around from max to mid etc that seems ok. Checked the shock after riding pressure was 240 psi. The shock only used about 60% travel whole ride and the shaft had a small amount of oil built up on it. So i wonder why sag is too much or not very adjustable but the shock doesnt use all its travel????