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Gearing question on cyclocross frame

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Gearing question on cyclocross frame

Old 07-31-09, 12:08 PM
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aboyd
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Gearing question on cyclocross frame

I bought a Motobecane Fantom cross last year to use as my commuter and occaisional after work ride. I normally ride my Giant OCR for weekend and evening road rides, but wanted something that would take a beating and accept wider tires for sloppy winter commutes. Anyway, the Motobecane has a 48/39 crank set and 12-26 cassette. I have recently started riding this bike a little more on hilly rides, and I suck at hills. the 39/26 combonation just ain't cutting it on hills for me. I would like to consider a MTB cassette, like an 11-32, but I believe I will have to change my read deraileur to a MTB with a long cage??? Any thoghts or experience with this? It has a short cage 105 rear deraileur now. Thanks
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Old 07-31-09, 12:45 PM
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get a compact crankset.

swap chainrings as needed.

for cross: 34/46, 36/46
for road: 34/50, 36/50
or there abouts.

the chain length will be the same between the two and will be sized for the 50T
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Old 07-31-09, 01:38 PM
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Replace the 39T chainring with a 34T.
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Old 07-31-09, 02:15 PM
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Well, now I guess that would be an easier solution. I have never swapped a chainring, is it very difficult? I have swapped cranks, but a chainring would be cheaper.
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Old 07-31-09, 02:19 PM
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I hate how narrow CX chainring combos are. I have a 36/46, and it just isn't that much help on hills. At least my legs are starting to grow into it, but it does limit some of which hills I will tackle in the area for now. I just can't wait until it's worn enough to justify dumping the whole thing for Rival.
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Old 07-31-09, 02:40 PM
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Not that big a deal putting on a long cage RD, but a bit of a pain if you want to swap back and forth.
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Old 07-31-09, 02:43 PM
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Originally Posted by Bah Humbug View Post
I hate how narrow CX chainring combos are. I have a 36/46, and it just isn't that much help on hills. At least my legs are starting to grow into it, but it does limit some of which hills I will tackle in the area for now. I just can't wait until it's worn enough to justify dumping the whole thing for Rival.
There's a reason for that... if you race cross. If you are just riding on the road, a compact double (34/50 or 36/50) is probably best.

FWIW, my racing 'cross bike this year will have 39/45 chainrings. How's that for narrow?
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Old 07-31-09, 02:45 PM
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Originally Posted by MONGO! View Post
Replace the 39T chainring with a 34T.
Probably not possible without replacing the entire crankset for a compact with a 110mm BCD.
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Old 07-31-09, 02:51 PM
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I am leaning towards replacing the entire crankset. I am running a Truvativ Elita crank now with a GXP BB. I know (or at least I believe I know) that a Shimano crank will require a BB swap also, correct? Would it require anything else? I am going to look for a compact Truvativ in 50/34, but so far I only saw 50/36. I would prefer 50/34, but also want to factor in the cost. Thanks so much for the input....
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Old 07-31-09, 03:57 PM
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Originally Posted by Brian Ratliff View Post
Probably not possible without replacing the entire crankset for a compact with a 110mm BCD.
True, didn't notice it wasn't 110.

Why would BD make a cross bike without putting a compact on it?
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Old 07-31-09, 04:04 PM
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Originally Posted by MONGO! View Post
True, didn't notice it wasn't 110.

Why would BD make a cross bike without putting a compact on it?
It was cheap, probably. But most cross bikes for competition have a 46/39 on them. If you need anything lower than that, it's probably faster to dismount and run. Also, dropped chains are a huge thing in cross. Much more of a problem then on the road. Having closely matched chainrings decreases the risk of the dreaded chain drop.
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