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Tandem Tom
12-30-12, 03:51 PM
Though I posted this in the Tandem Forum I thought that the wisdom over here would be just as great!!
The timing chain rings on our tandem have a few small burrs on some of the teeth. I was wondering about taking a file to them?
If they're new, the chain will shave them off by itself, so if the chain runs now, feel free to ignore them. On used rings the burrs aren't really burrs, but peens. The rollers roll up the teeth and flow metal to the sides, much as a rolling pin makes dough wider as it passes. The process is self limiting since the insides of the inner plates will wear that material when it gets too wide.
You're more likely to see this type of flowed burr on tandems, single speed and IGH bikes because the chain runs straight so there's less side wear dressing the teeth. On derailleur bikes the chain coming from the sides wears the flanks of the teeth so it's rare to ever see this type of burr. (I only ever see it on the inner side of my inner road ring).
You can file them off it you prefer. It doesn't make any difference either way.
Also note that this burr formation is usually an indicator of a stretched chain, or one running too tight.