Join Date: Apr 2009
Location: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
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Originally Posted by robgod
Thanks for all your replies.
I'm now not sure if its the chainring that needs replacing or the chain (or both!). When comparing the chain to a new one, the old chain is visibly longer over just 5 or 6 links! (You can see from the photo where the chain is slack around the chainring) Do chains actually stretch?
Oh, and mechBgon - thanks for that. And apparently, Icon is a brand name for Trek. You get the bonus point
Yes, chains stretch, but not the way your old elastic wasteband does. In chain "stretch" there's no distortion or elongation of the metal, but rather that the individual links can move apart as the pins and holes that connect them wear. That elongation increases the pitch causing what you're seeing. Looking at the photo, I suspect that both are worn to or past the point of replacement.
In your shoes, I'd replace the chain first, and then the chainring and possibly the cassette if necessary. Necessary meaning that the new chain skips under load.
For future reference, measure your chain and when 24 links which should measure 12" "stretches" out to 12-1/16. Rerplacing the chain before it's worn too far, saves the cassettes and chainrings.
An ounce of diagnosis is worth a pound of cure.
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