Touring - Crankset / chain compatibility

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bullwinkle
09-26-08, 02:19 PM
I have a question, guys. I tried posting this over in the mechanics forum, but no responses yet. Maybe y'all can help me here ...

I currently have a Campy compact crank and 10-speed drivetrain on my touring bike. But, I'm planning a hillier tour next summer and want to get some lower gearing by replacing the crankset with a triple. Campy makes a 10-speed triple crankset for the road, but it's granny has 30 teeth (only 4 fewer than my current compact). If I were to go with a mtn bike triple, I could easily get down to about 22 teeth on the granny. But mtn cranksets are all 9-speed from what I can see. Would my 10-speed Campy chain work with a 9-speed crankset?

northboundtrain
09-26-08, 03:12 PM
According to Sheldon Brown's site http://sheldonbrown.com/harris/chainrings.html you can go down to a 24 tooth granny ring on a standard road triple. Though he doesn't address 10 speed chains on 9 speed chainrings directly, his paragraph at the end of this page suggests you could use a 9 speed crank if you want.
bwgride
09-26-08, 09:35 PM
Campy makes a 10-speed triple crankset for the road, but it's granny has 30 teeth (only 4 fewer than my current compact). If I were to go with a mtn bike triple, I could easily get down to about 22 teeth on the granny. But mtn cranksets are all 9-speed from what I can see. Would my 10-speed Campy chain work with a 9-speed crankset?

Chain size should be similar between 9 and 10 (as long as Campy chains are similar to others such as SRAM and Shimano). However, a few possible issues to note:

1. The current bottom bracket will probably not be compatible with the MTB crankset. If it is square taper, Campy's are different from JIS standard.

2. The front derailleur may not be able to handle the smaller crankset -- mount the crank and give it a try.

3. The rear derailleur may not be able to handle the extra chain wrap that may result from the smaller crank -- mount the crank and see what happens under different gearing combinations while the bike is mounted in a work stand.