Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.


Old 06-21-17, 05:36 PM
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recently got some Sram rival 1 gxp cranks as a present and wanted to install them on my stock All City Nature boy disc to give it a little upgrade. Went to my LBS and now i can feel a rubbing sensation occasionally when pedaling. First was told it could be my pedal bearings, switched those out with no luck. then possible chainline issues, put a different chainring on and problem is still there. are these new cranks just not going to work? Any help appreciated!!
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Old 06-21-17, 07:53 PM
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chainring swap has nothing to do with chainline, Is it single speed ? a slight feel through the pedals with a new crank is more likely to be a chain wear issue if you have a fresh chain chuck it on and go for a spin.
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Old 06-21-17, 08:39 PM
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It might be hard to describe, but I think you might have to get more specific than "a rubbing sensation". Does it feel like the cranks are dragging on something? Chain dragging on something? Your foot on the crank arm? It's a two-piece crank, meaning its spindle is permanently attached to the drive side crank arm, so you shouldn't have a chainline issue as if you were using the wrong spindle length.

It would be a whole lot easier to observe in person, unfortunately.

If you're only noticing some drag when you spin the pedals by hand, it could simply be bearing seals. New ones tend to be a little sluggish and break in with some use.

Last edited by SkyDog75; 06-21-17 at 08:43 PM.
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Old 06-21-17, 08:45 PM
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The solution lies in finding exactly what's rubbing and why. Chainline would only be a factor under limited circumstances, for example if the crank were too close or too far and beyond the limits of the front derailleur's range.

Obviously I can't see the bike, but if someone is suspecting the bearing, or it has the sound and feel of bearing drag, then possibly a crank axle spacer is touching a bearing seal, or something similar.
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Old 06-21-17, 08:56 PM
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Old 06-22-17, 08:26 AM
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Since the "Nature Boy" is a single speed, and disc, I'd check two things first. Make sure you have some "slack" in your chain, and it's not the brake rubbing.

Beyond that check the BB installation. Some get confused and install the bottom bracket with the supplied spacers or shims. You don't use them on GXP road cranks (which Rivals are) on a road frame (68mm shell width.)

Not solved yet? Remove NDS crank arm and re-install as per instructions. After torquing crank arm take a mallet and give both ends of the spindle a "little whack." If the problem still exists I'd check the bottom bracket shell conditioning.
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Old 06-22-17, 09:42 AM
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'chain line' is a parallel line to the bike's centerline..

On multi speed derailleur bikes it's the middle cog on odd numbered ... speeds, 3,5,7,9, 11

Or the gap between the 2 most central cogs if the number is even,

lining up with the middle chain ring of a triple (or your 1 by), or the gap between the 2 chainrings in doubles.

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