I am in front of a big decision. Wich crankarm is better in weight/stiffness?
I heard that carbon arms (like FSA) are not too stiff.

FRM CU2-M TR ISIS / Race Face Next LP ISIS / FSA Carbon Pro Team ISIS

My bb decision is FRM's ISIS. Still not sure 113mm or 108 better for CrossCountry/Marathons. I know the official size for all of them is 113mm.

Please help me if you know any information!

If you've chosen the FRM bb Al-version you can take the crank of your choice without having a look at stiffness, cause the stiffest cranks don't make sense if you're loosing stiffness at the bb.

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to find out the BB lenght. upright the BB and take a ruler and measure from bottom end to top end. If u wanna find out which one is the best crank , try and for www.mtbr.com

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Crashman like crashing, feel the rythem and ride.

I disagree. Im using bontrager crank with xtr Un91 BB. I broke my left crank arm with a snap as i was struggling climbing up a steep slope.And the square BB work just fine.

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Crashman like crashing, feel the rythem and ride.

Ok, you broke it, but that doesn't have to do s.th. with stiffness. In most cases the stiffer the longer they last, but a flexy fork for example must not break. I was aiming for the "powerloss" caused by flexy crank arms, not for durability. So what I meant is:he won't feel a difference in stiffness between these crank arms because of the FRM bb with Al-axle, but I agree that some light crank arms don't last very long.

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