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Old 01-06-08, 08:24 PM   #1
Rumblejohn
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Chain ring question

I have a Raleigh hybrid with a Suntour crankset, and the chainrings are starting to show some wear. As they are riveted on, can they be replaced, or is it time to up-grade the crankset?

Thanks, John
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Old 01-06-08, 08:26 PM   #2
Sheldon Brown
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Originally Posted by Rumblejohn View Post
I have a Raleigh hybrid with a Suntour crankset, and the chainrings are starting to show some wear. As they are riveted on, can they be replaced, or is it time to up-grade the crankset?
Depends on the model. Cheapos are riveted, better ones are held by Allen bolts.

Here's some boilerplate that may be relevant:
Back in the old days, every tooth on a chainring was the same as every other tooth on that ring.

Beginning in the 1980s, however, Shimano started experimenting with different shaped teeth in different parts of the chainrings, with the aim of improving shifting.

Newer chainrings typically have some teeth much shorter than others, usually the teeth that are picking up the chain when the cranks are vertical (this is when chain tension is lowest, and is the best time to make the shift.

These special stubby teeth, often coupled with "shift assist" pins and ramps on the side of the chainrings, make a great improvement in shifting.

However, one drawback of this is that folks who aren't aware of this design will sometimes discover the short teeth and will assume that their chainrings are damaged or worn out! They aren't!

It is very rare to actually wear chainrings out, takes many, many thousands of miles with a worn-out chain. When a chainring is worn out, _all_ of the teeth show the wear, usually acquiring a hooked appearance on the sides of the teeth that drive the chain.

For further information on this, see: http://sheldonbrown.com/chains

Don't be embarrassed about this...this is a _very_ common question, so common that I have prepared this generic boilerplate response to save re-typing.

All the best,

Sheldon
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Old 01-06-08, 08:53 PM   #3
Rumblejohn
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Thank you very much! That helps explain why the front shifts much better when not under load.

John
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Old 01-06-08, 09:13 PM   #4
Sheldon Brown
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Thank you very much! That helps explain why the front shifts much better when not under load.
Fronts always shift better when not under load, because the front uses the top run of chain to shift, and that's the part that is delivering power.

The rear derailer shifts with the bottom run of chain, which doesn't get any tighter no matter how hard you pedal.

Sheldon
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