The backside of my rear derailleur (first picture)has quite a lot of wear and it looks like the chain is also rubbing on the inside (second picture).
I recently installed a new shimano chain and followed their guide on chain length, b limit and indexing etc. I don't think any of the marks or damage were there before I installed the new chain so could it be linked to that?
by GrimwithShore
3 Comments
A wild guess- something hit the outside, bent the frame and now chain is rubbing on the inside. Try switching different gear combinations and check if there is no chance that at some point gears are hitting on the outside of frame
Upper pulley wheel location is looking dangerously close to the largest sprocket on your cassette. Probably need more photos to evaluate but the sharper scrape marks suggest that the cassette is making contact and pinging off the cage. I’d put it on a stand and test gear changes in the lower range.
My guess is a derailleur hanger bend allowed it to hit the spokes. Shift to the biggest cog and check for rubbing, as another commenter said this could also be the cog being too close to the pulley.