My bike (stumpy evo) has done this from new . When the trail gets rough and I try to pedal the chain is jumping up the rear cassette meaning I can’t get any power down.

I’ve changed it from 2x to 1x , fitted a chain device

It looks like this although now with sram chain and xt block.

It also does it when going over potholes, any idea’s anyone.

bent hanger and/or rear mech cage

Oh sorry i forgot to say that I’ve just had a new hanger fitted . Like I said the its done it from new so I was ruling out the mech.

Don’t know much about those mechs but is there enough outer there ?

(and what happens to cabling when the suspension is fully compressed?)

Chain growth. Let the air out of the shock, cycle it through its travel and see what happens. My guess is the chain is too short.

Yeah I’ll give that ago but what am I lookin for. My LBS (who are pretty good) have set up and checked everything including the cable lengths (actually they replaced that as well).

Would the internal cable routing in the chainstay be the problem?

Correct spacers on the bottom bracket?

If you’re anywhere near Farnborough, Hampshire, or Isleworth, West London, give me a shout (email in profile) and I’ll have a look at it for you. I love sticky little problems like this, but it’ll be virtually impossible to diagnose without seeing the bike. 🙂

That’s very kind of you to offer Peter but I’m in Cheshire.

There is a little play in the rear mech (side to side) but the shop assures me that its fine.

So does nobody else suffer from this problem ?