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I've just bought a used road bike. after I arrived home I noticed one of the chain ring teeth was snapped.

I have a spare flat bar bike which I believe to be much newer than the one I bought.

Because of that and the snapped tooth I've had the idea of replacing the parts with parts from my old bike, rather than investing in a new chain ring.

Can you give me your thoughts please?

More images at http://imgur.com/a/w5IZr

enter image description here

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    Now you other bike has a worn chain ring. Why not just buy a new chain ring? – paparazzo Aug 2 '17 at 16:14
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    Those "snapped" chainring teeth are normal -- they're there to aid chainring shifting. – Batman Aug 2 '17 at 16:17
  • Yes I could buy another if I had to. aiding shifting.. It's only one tooth?. All the rest are fairly even. – Martin Aug 2 '17 at 16:40
  • The tourney chainring doesn't look replaceable. You'd have to replace entire crank. – ojs Aug 2 '17 at 19:45
  • Yes you could be right. I had a quick look today and it looked like the crank rings are riveted together. – Martin Aug 2 '17 at 20:15
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That chainring doesn't look particularly worn from this angle. The wear would make the teeth look less symmetrical and more like shark fins. That shorter tooth allows the chain to leave that ring more easily when you change gear.

Ensure the chain is not worn out using a gauge (see http://www.bikeradar.com/road/gear/article/bicycle-chain-wear-explained-46015/ for what types of gauge are available and how to use them). If you grab the chain at the front of the chainring and pull it away from the crank spindle, you shouldn't be able to get more than about 1mm of gap between the chain and the dips between the teeth.

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