Cyclist0108

My kid's bike has a Roxshock Reverb dropper post. I was helping him with some maintenance and had the seatpost (the extended part) clamped. He claims I damaged the post doing this, and that it no longer activates when at the slowest setting.

Is this really that fragile, and more importantly, is there anything I can do to fix it (assuming it is even broken)? It seems to work fine to my untrained eye. The only things I can think of is I mixed some air and hydraulic fluid in the remote activation hose, or I very slightly bent the seat post (which I have no evidence for).

Asi

Most probably you did no damage at all.

Check this video on the subject:

cpach

You're unlikely to have done significant damage to the post clamping the extended portion. The biggest deal is suspending the bike from the upper seatpost or seat when the post is not fully extended--it pulls on the hydraulic lockout and tries to pull air past the IFP. Otherwise, it is a sliding surface and wear to the upper post can effect the smoothness of the post so I generally do not clamp dropper posts by the upper post--it mostly involves an annoying amount of marking posts with tape and carefully feeding the hose through the frame as I raise the bike to put it in the stand. Also check the seatpost clamp torque--overtorquing compresses the lower post and degrades performance; the post should be installed with carbon assembly paste (regardless of frame material) with the minimum torque to consistently keep it from moving.

Also there may be air in the line, which is relatively easy to bleed. You basically need the bleed syringes and reverb fluid and you basically push fluid from one to the other until there's no more air, then close the lever port and push the lever firm and close it up. The syringes are the same as SRAM/Avid brakes, but you don't want to reuse them because DOT is corrosive and the reverb fluid is not.

Also like all moving things friction is the enemy. An easy quick fix it to run slick honey on the upper post and cycle the whole thing. Better yet is to partially disassemble the post to clean and lube the outer post and its bushings and guide pins. If the post actually starts feeling soft it needs a rebuild, which is like a $70 kit and usually $120-150 labor in Santa Cruz (it is a genuine pain in the ass, though I've gotten much faster at it).

Cyclist0108

@cpach Many thanks, as always, for your advice. I'm about to leave town for a few days but will have a crack at it when I get back. If I can't get it to work to his totally unrealistic and exacting standards, I might have to bring it to you...

The main symptom is if I set it to the slowest setting, the post won't move at all, and the fastest setting allows it to spring up about where it used to be in the middle of the range.

bikeme

Did you happen to tighten or loosen and retighten the seat tube collar? If you clamped it too hard, that can hinder the sliding of the moving shaft.

Cyclist0108

No, unfortunately. I even loosened it up for diagnostic purposes.