How much chainring wobble on a new Sora crank?
06-05-13, 07:35 PM
#26
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How do you know it's not the bottom bracket ? OP said he changed the crank. Then all the discussion is about the rings and spider. If it is threaded on incorrectly, wouldn't that manifest as out of alignment ?
06-05-13, 07:59 PM
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I don't see how the BB can cause wobble on the stand.
The axle spins relative to the BB, and the chainrings should only be in a plane perpendicular to the axle. So an off BB might make the angle of the plane off, but not cause the chainrings to wobble out of the plane.
The axle spins relative to the BB, and the chainrings should only be in a plane perpendicular to the axle. So an off BB might make the angle of the plane off, but not cause the chainrings to wobble out of the plane.
06-06-13, 07:44 AM
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Yeah, I think you're right. The BB could cause rubbing, through misalignment, but not wobble or eccentricity {sp ?** Right ?
06-06-13, 12:15 PM
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I recently installed an alfine crankset on my dad's bike (3x7 to 1x7). It seems to have some wobble, I'd say between 0.5mm and 1mm. It's easy to spot since the chainring is so close to the chainstay.
The frame is 15 years old and I just filed down the paint instead of having the BB faced. I don't know if that makes a difference; it turns very smoothly so I don't think the bearings are far off. I'm guessing shimano just OKs any crank with less than say 1mm of wobble, so you can get lucky or unlucky but it's never disastrous.
The frame is 15 years old and I just filed down the paint instead of having the BB faced. I don't know if that makes a difference; it turns very smoothly so I don't think the bearings are far off. I'm guessing shimano just OKs any crank with less than say 1mm of wobble, so you can get lucky or unlucky but it's never disastrous.
