Chainring wear

I gave my bike a good cleaning the other day. While I was scrubbing the chainrings, I noticed something odd on the larger one. There is one tooth that is shorter than all the other teeth by maybe about 2 mm. All the other teeth look uniform and they all show similar not-too-bad wear. But I don't get why the one tooth is shorter. I'm not sure if it was always that way and I just hadn't noticed it, or if this is a recent development. Is this an abnormal wear pattern and is it something I should be concerned with?

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Originally Posted by malaholic

There is one tooth that is shorter than all the other teeth by maybe about 2 mm.

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Just one?

Quote:

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Originally Posted by malaholic

But I don't get why the one tooth is shorter. I'm not sure if it was always that way and I just hadn't noticed it, or if this is a recent development.

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It is normal (common?) to have a few shorter teeth - they're meant to help with gear shifting.

In today's mail I received several new 6 year old "big" Shimano MTB chainrings. Looking at them, they have two sets of shifting "pins". Just after each set of pins (that'd be counter clockwise) are two shorter teeth. Plus, in the two intervals between the shifting pin groups, seperated by three normal teeth, there are a pair of pointier teeth.


Last summer I went through this same worry with my old MTB. I've essentially never used the original big ring. It's purpose in life seemingly was to be a 42 toothed bashguard. Yet, it too has the shorter teeth. I originally thought that they had been broken off from all the times I banged the chainring on a rail while walking the bike across railroad tracks.

Hmmm....good to know, thank you! On the other hand, I guess I now do not have a sound excuse for why I'd need to upgrade...um, I mean replace it. :)