Join Date: Apr 2009
Location: Boulder County, CO
Bikes: '92 22" Cannondale M2000, '92 Cannondale R1000 Tandem, another modern Canndondale tandem, Two Holy Grail '86 Cannondale ST800s 27" (68.5cm) Touring bike w/Superbe Pro components and Phil Wood hubs. A bunch of other 27" ST frames & bikes.
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Want to use 10 speed triple mountain bike crank w/SRAM X.9 components which are 9sp
Okay, I've got a mountain bike which I can't comfortably ride because the cranks are too small. I want to replace them w/180mm cranks. I ride 205mm cranks on my road bike, so don't bother posting that there isn't a difference as I'm not an average size cyclist. The 175mm cranks make me miserable trying to climb any kind of hill even with low gears. You try riding 165mm cranks if you don't think it would matter.
The problem is that I just bought the bike. It came with SRAM X.9 9 speed components and an SRAM/Truvativ Stylo crank with 175mm crank arms.
I want to know if I can use a 3x10 crank or if a 3x9 crank would shift better. Of the cranks I want, Race Face Turbine the 3x9 is more expensive by about $75 than the 3x10 where I'll be buying it.
Now here is the punchline: I'm not going to be using the SRAM X.9 front shifter. I hate not having adjustable front trim, so I'll probably be using an old XT thumbshifter or something similar. Not worried about whether the SRAM X.9 shifter will align correctly, as I won't be using it. I am worried about whether using the XT friction shifter whether a 3x10 crank would shift poorly with a 9 speed chain. I don't want to use a 10 speed chain as I'm a pretty big cyclist and already I'm worried about breaking chains.
Which leads to another question: What is the difference between a 3x8 crank a 3x9 crank and a 3x10 crank, aside from the rings (and whether the BB is square taper or external)? Is the spacing from the center of the tooth to the center of the tooth on the higher and lower rings (on a triple) the same on 8sp, 9sp, and 10sp cranks? I'm wondering if the cranks are like cassettes where the spacing becomes narrower.
The reason I ask is I might completely convert to an 8sp drivetrain to get the stronge/thicker chain/rings/cogs. So if I could use an 8sp crank w/modern rings that would be a flexible option as well. So could I use a 10sp crank w/8sp rings?