Road/cross double cranks and their q-factors

[rice rocket]

I'm having an issue on a CX frame with the crank arms hitting the chainstays. They were SRAM/Truvativ Elita cranks, the GXP version, and it wouldn't rub when you pedal it on a stand, but put any weight on it and the frame would flex and the crankarms would rub.

I threw on a spare Shimano Sora triple for the time being, but I'd like to go back to a double. Any ideas? I measure ~117mm wide from chainstay to chainstay at the end of the crankarms, but Q-factor is measured at the pedal-side of the cranks, not on the inside.

[oliver1850]

I've got lots of different setups I can measure. What's your preference as to brand? Do you want to stick with external cup designs?

[rice rocket]

Oliver, that would be great. I don't really have a brand preference at this point. I have the tools for external BB and some for the square tapers, but external would probably be the lightest (gf's bike, any weight off to make it more maneuverable is a plus). The Sora I have on there now is square taper and probably 3+ lbs.

Even if you just get the crank arm thickness, I can subtract from the published Q-factor numbers and find what I need. Thanks!

[oliver1850]

I measured the R700 on my Ritchey at 118.6. That was 46 (to the seat tube) on drive side, 44 on non drive, + 28.6 for the seat tube. That's a 175 crank, not sure how straight the inside surface compares for different lengths. Rival OCT measures the same on a bike with a 32 seat tube, so 122 for it. Also a 175.

There are other things I can check: Octalink Tiagra, 5500, 6500, 7700, Shimano square taper, and all sorts of Campy. No sense in checking stuff that you wouldn't be interested in though.

[EricEstlund]

FSA publishes their Q #'s on their web site- seems like working back would help.

The new gen of double mtb cranks would probably fly, and may give you some nice gearing depending on her cross needs.

The White cranks may also be a nice option with the adjustability of sq taper and loads of gearing choices.

[oliver1850]

Centaur UT cranks are labeled 145.5 right on the arms. Subtract 2x the 14mm arm thickness and you get 117.5. I'm guessing you might want to avoid them for your application.