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10 speed crank on a 135mm road bike too close to the stays?

by Fish_n_Chips
Tue, May 10, 2016 16:46
6

Hi,

I'm transferring my old road 10 speed setup to a new road frame but finding the double chainset pretty close to the stays with a 135mm axel.

Does the 135mm make a difference?

I'm thinking the chain line is off by 2.5mm on the 68mm BB. Could buying a mtb or CX chainset would be better?

It's a SRAM GXP compact chainset 10spd made for 68mm so you can't adjust with spacers.

The Shimano CX 50/70 looked like an option but cannot find any info if it fits a 68mm for 135mm rear triangle.

Any help? 1

If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.

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6 comments

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Fish_n_Chips | 7 years ago
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I found it does work well on the larger sprockets and larger chain ring.

One thing I just tried is using a 34 and 50T chainring and I can use 34T and 13 (from 11-28) and to be honest need shifting to the larger chain ring.

Might try a 48T if I can find one.

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joemmo | 7 years ago
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If the cranks are not striking the stays then theres's really no problem there. As for the chainline, 2.5mm will, at worst, mean you need to change down at the front one sprocket earlier. On the plus side, you get a better chain line across the lower end of block on the small ring. 

 

If nothing is rubbing, grinding or exploding then it will be fine. FWIW I have a 1x10 with a GXP chainset on a 135mm rear end, the chainring is in the outer position and yes, its not ideal on the big sprocket but its perfectly ok around the middle of the block where you spend most of the time.

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Fish_n_Chips | 7 years ago
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Not on SRAM GXP crank.

The spindles are shorter than mtbs. A spacer will cause the crank to grind on the bearing. However a mtb GXP 73mm crank could be used as the spindle is longer.

If a Shimano road/CX crank could be spaced out then that would work.  Looking in Shimano tech docs, there is no spacer unless you have a mtb chainset.

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philhubbard | 7 years ago
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I think I'm right in saying you should always have at least one drive-side spacer on any 68mm shell bb

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CXR94Di2 | 7 years ago
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Can you not try a spacer on the drive side?

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TypeVertigo | 7 years ago
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I've swapped in a Shimano 105 FC-5750 crank into my TCX, which does have 135 mm QR dropouts due to the disc brakes. The TCX is based around a BB86 shell, which is as wide as your typical 68 mm BSA shell with external BB cups screwed into it, so the effective width is 86.5 mm.  I do notice that the crank arms are very close to the chainstays, but I haven't had any interference or rubbing issues with these parts.

If you end up using either of them, the CX50 and CX70 cranks are broadly similar to the FC-5750. I hope this helps.

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