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
Mentioned: 2 Post(s)
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There's n o way a chainring can become ovalized. It's either a designed oval or Biopace (or whatever) ring to start with or it's not.
OTOH- if the rise and fall are very slight, say about 1/16" or less, then it's very possible that the chainring isn't mounted concentric on the spider. This has always been a non-issue on derailleur bikes, but can make setting chain tension (slack) difficult on a single speed ot IGH bike.
If this is an tour issue, the ring can usually be centered by loosening the mounting bolts until it's held firm but not tight. Rotate the crank using your finger or a something as a reference to find the high spot, then tap the ring toward center with a wooden block or mallet. Do this a number of times, working on dialing it in by degrees until it's as good as you can get it. Don't forget to tighten so it stays put, then readjust the chain tension (no tension/minimal slack) based on the tightest place.
EDIT, you posted the photo as I was writing.
This crank combined a round outer ring with non-round inner and middle rings. The assumption was hat you'd get the most benefit form oval rings when climbing where the cadence is lower.
An ounce of diagnosis is worth a pound of cure.
“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin
“One accurate measurement is worth a thousand expert opinions”
- Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance
Last edited by FBinNY; 09-08-14 at 10:38 PM.