Originally Posted by
zacster
Well, here's the kicker. I broke out my Park Cyclone Chain Cleaner that's been in the plastic unused for 2 years now, and cleaned the chain. It was of course very worn out, made obvious by the cleaning. But what I also discovered was that the frame DOES have a crack in it, on the chain stay. I had not noticed it before, but it looks like it was there for a while.
I'm not concerned about the crack, the frame is aluminum it doesn't seem to effect the ride. If it fails, it fails, I'm not very attached to this bike.
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If the right chainstay is cracked it's entirely possible hat it's deflecting abnormally under load. Movement of the stay might be shortening it slightly, allowing a bit of extra chain slack and moving the RD outboard a hair, just enough to make a shift.
Depending or where the crack is, you might be able to improvise a splint using sheet steel and hose clamps. A decent job will last until a new unrelated crack elsewhere kills off the frame.
BTW- if you want a nice cable cutter, I have a bunch of New old stock,
old jagwire cable cutters (blue handles, same as the Shimano of that era). I'll sell you one for $19.00 including postage within the USA.