What size (170 vs 175 etc) cranks do I want for my new Rocky Mountain ETSX? I am 5'10" and pretty normal proportionally as far as torso and leg length. I'm pretty much an XC rider. Also, I'm not much of a mechanic, so how do I even know what cranks will work with the bottom bracket that my bike comes with? I'm getting the ETSX 50, but upgrading a bunch of the parts, and have heard marginal reviews of the Race Face Evolve XC cranks that come on it.