I have just purchased a bike with a Shimano 34T sm-cr82 chain ring and crank set. Is there a 30teeth chainring that you can put onto it to make it easier to ride uphill?

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    I've seen grannie gears down to 26 teeth and probably lower. However most derailleurs don't cope with differences of more than 13-14 teeth. If you have a single chainring, the normal is to add larger rear gears - I think sram do a 50 tooth largest cog now.
    – Criggie
    Jun 10, 2017 at 5:52

1 Answer 1


The smallest SM-CR82 is 34t, but FC-M820 and FC-M825 (one of which is your crank model) can take other 104 BCD rings, down to 30t. 30t 104 rings are a somewhat recent hack/innovation and have to play some tricks to be able to physically work without interfering with the crank (most or all of them have integrated spacers and threads). Most of the narrow/wide chainring makers have a version.

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