On my stumpy FSR with a X0 rear mech a problem has occurred and I’m in head scratching mode.

Basically all the gears work and indexed OK. Big ring and all sprockets at the back run fine and so does middle ring and all sprockets.

When I run the granny ring I can use all the sprockets at the back cool. However, when I start going up any incline the rear mech kind of jump/kicks forward and sounds like a bucket of nails.

Any suggestions ???

PS New chain and cassette and middle ring installed yesterday. But did this problem before anyway.

chain too long so not enough tension in the mech?

could be the freehub slipping under high torque too?

Chain suck. Either replace granny or attack it with a file to remove burrs and tops of hooked teeth.

@wwaswas
Thanks.
I will check the chain. But I’ve always replaced the chain like for like over the years with no problems. But will still check it again though.

@bigjohn
Thanks.
I will check the granny for sure.

When you put the chain under load it moves round slightly on the chainring so the “release” behaves slightly differently from when there is no load.

Middle ring changed.

Chainrings by SGMTB, on Flickr

I will get filing on the inner. Or order this:
http://www.chainreactioncycles.com/Models.aspx?ModelID=9235