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Need some crankset advice!

578 views 3 replies 4 participants last post by  turbodog 
#1 ·
Greetings, all!

I'm primarily a roadie and I'm currently building a bike to do a combination of road riding and unimproved roads/trails with (we've got plenty of 'em here in Virginia!). Should also mention that even the paved roads here in the foothills of the Blue Ridge can be pretty challenging-there isn't any flat riding anywhere in my 'hood!

I'm using a cyclocross frame to give me a longer wheelbase and room for fatter tires, and now I'm trying to suss out the best gearing for my intended use. The bike will have SRAM Rival double-tap road shifters, so I can't even consider a triple. I guess you could say I'm trying to find the sweet spot where I can get up the hills while maintaining a decent cadence without resorting to a granny gear.

The road biking world hasn't gotten hip to setting up a compact crank with anything but a 50-34 on a 110 bcd pattern, and you can't go any smaller than 34 on a 110 bcd, so I'm coming to you guys to help me out here. I think using a 104 bcd mtb crank (w/170mm arms) with appropriate chainrings--say, 46-30 or 48-32--and a SRAM 11-28 cassette will function better than going with a 50-34 road compact and an 11-34 cassette (which necessitates the use of a long cage derailleur). I welcome your input!

I don't mind sacrificing a bit of speed on the high end to achieve better climbing gears on the low end. Can I convert a 104 bcd triple by just deleting one chainring (inner or outer) and doing a bit of mixing and matching of chainrings? Are there certain models of mtb crank that might lend themselves to this better than others? What are the technical issues I need to consider?

I'm into function, not form (no bling necessary)-I just want a crank that'll do the job, but I'm really unfamiliar with mountain bike cranks. It would be nice if it was relatively light, but I've counted grams everywhere else on this project, so I'll take what I can get crank-wise. I should mention that my frame has an Italian threaded BB shell, so I need a crank that's compatible with a 70mm wide x 109.5mm spindle length Italian threaded BB. I know I can find a square taper or ISIS that will fill the bill-not so sure about the Octalink V2 (V1 is available in this configuration).

What are your suggestions on a crank and chainrings for this puppy? Anybody have any of these components in their surplus parts bins/boxes/drawers/piles they'd be willing to part with? Any and all assistance will be gratefully accepted!

Thanks a million and
Live Out Loud!

Aden
 
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#2 ·
Another possibility to consider is using a triple crank, and using the granny and middle positions. That will give you the freedom to go below 30t for the low, combined with something like a 42 or 44t chainring. With an 11-26 cassette starting you'd get a reasonable high gear, and a good selection in the mid range. Or with a 11-32 cassette for a wide range. You'd ride it like a 1x9 plus granny.
 
#3 ·
Specialties TA Carmina from peterwhitecycles.com with the 94 mm Double spider will give you the chainring choices you want. Square Taper, get a Phil Wood BB.

You mentioned "I should mention that my frame has an Italian threaded BB shell, so I need a crank that's compatible with a 70mm wide x 109.5mm spindle length Italian threaded BB.", you would want to research the spindle length for these cranks, there's a bit of info on them on the peterwhitecycles.com site.
 
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