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Old 09-08-14, 10:13 PM   #1
spinachface
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Chain going up and down. Ovalling chain ring?

Just got a bike on craigslist and as I'm going through and making it my own, I go to clean and lube up the chain. As I'm back pedaling though, I notice the chain going up and down. It'll start here _ and about half way through the rotation go here - (very crude example, sorry).

Hoping I didn't get a dud, but any suggestions? Potentially a chain issue? The bike is an older Fuji Touring bike (Saratoga).

Thanks!
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Old 09-08-14, 10:20 PM   #2
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As I look at a non existent photo or video I don't see any problem But seriously it's pretty obvious if the rings are not round and one would hope that you could figure out how to spin the crank while watching the ring's top edge and see if it varies in relation to the frt der cage bottom. If the rings prove to be round then suspect a well worn out chain that won't settle fully into the teeth any more. Really a visual aid would have helped. Andy.
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Old 09-08-14, 10:30 PM   #3
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Really a visual aid would have helped. Andy.
Good point! haha. I took a picture of the crankset. Seems a little … off for some reason. Any thoughts?

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Old 09-08-14, 10:35 PM   #4
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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.
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Old 09-08-14, 10:36 PM   #5
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I believe you have what is called an "Ovaltech" ring. They are not round if so. The ring's teeth look to be in decent condition and the chain seat well on the granny. I suspect you are only seeing the non round ring shape when you spin the crank. Andy.
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Old 09-08-14, 10:44 PM   #6
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Awesome! Sound like the whole oval chainring thing is a little gimmicky, but if it gets me where I need to be, I'm content!
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Old 09-08-14, 10:56 PM   #7
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Awesome! Sound like the whole oval chainring thing is a little gimmicky, but if it gets me where I need to be, I'm content!
It doesn't. You do that by turning the pedals.
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