Lbs changed the piston air shaft to 120 from 100 , nice and plush but omg bang at the top of stroke , what’s gone wrong? Sounds to me like metal on metal.

Possibly forgotten to put in the top out bumper

Yep sounds like that. Definitely not right. Putting the air spring back in its easy to get the parts in the wrong order as they are all loose on the shaft.

GB

If they’re dual air check the negative air spring pressure.

Negative needs to be within 10psi of positive pressure, if it’s too low in relation to the positive they will top out.

I had same problem when I changed air shaft in my Reba. Mine was due to the damper shaft topping out before the airshaft which has the rubber stops on.
Not all rebas can go 120mm as I found on Web some have a shorter damper.

I got the guys at work to chop a bit off the air shaft so it topped out before the damper.

If you drop the lowers off and pull down both shafts the air should be shorter than the damper

Nightmare typing on phone hope you can understand what I’m saying

This is a very good point ^ Did your fork come on as part of a full build? iirc it’s OEM versions of the fork that are affected

OEM of Merlin Cycles , no box , pump or instructions.

If its a solo air fork you might need a new damper shaft they have to match the length of the air shaft..bring back dual air which was a lot simpler(cheaper) the synic in me thinks Sram changed to Solo air just because of the fact that a lot of people were changing the travel on forks easily so didn’t need to buy new forks so they made it more difficult & expensive. I upped the travel on my girlfriends Sid’s from 100 to 120 and it ended up costing nearly £150 in the end..

My forks were a from merlin too, Ive ended up with about 115mm travel rather than the full 120mm with chopping the air shaft

On the dual air Rebas, I find if you put a little bit more (5-10 psi) in the negative air chamber, it makes them feel a lot plusher. Not too much as this could reduce the available travel.