Does chainline usually wobble from right to left ae crankset spins?
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  1. #1
    RoadBikeReview Member
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    Does chainline usually wobble from right to left as crankset spins?

    Is it normal for a chain to appear to shift a little from left to right as the crankset spins? This is when the bike is up on a stand (no weight put on the crankset). Thanks
    Last edited by mwilcko2; 07-19-2007 at 06:20 PM.

  2. #2
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    I'd say no. Maybe a very slight amount might be all right. It could be that a chain ring or that one of the spiders on the crank arms is bent. What kind of crank is it?
    Before you criticize someone walk a mile in their shoes. That way when you criticize them you'll be a mile away & you'll have their shoes.

  3. #3
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    Straighten up

    Quote Originally Posted by mwilcko2
    Is it normal for a chain to appear to shift a little from left to right as the crankset spins? This is when the bike is up on a stand (no weight put on the crankset).
    Define normal. It is quite common, but you can fix it. Assuming that your BB is OK (i.e. not loose - it's extremely unlikely that it's bent), you have to straighten your spiders and/or chain rings. Hold a small screwdriver or other short, pointed object against the seat tube so that the tip just grazes the crank spiders as they pass. If the spiders are bent (most likely problem), you can even them out as follows:

    Place the bike on its side with the crank supported on a block of wood at the axle. With another block of wood or a stout dowel placed at the end of the offending spider(s) give it a whack with a hammer. Check for change in alignment. If you got no change, hit it harder next time. Repeat until all the spiders are even. You may need to bend them away from the frame (brace the right crank on the block of wood) or toward the frame (brace the left crank).

    Once the spiders are even, check the chain rings with the same technique except put the point of your screwdriver at the teeth of the rings (most likely the big ring only if the spiders are even). Straighten the chain ring by placing a large adjustable wrench over the ring with the jaws adjusted for a slip fit over the ring. Bend gently, and check alignment. Repeat until you've got it right.

    Even with the chain rings dead straight, you still will get some deflection due to pedaling forces, but that should greatly improve your situation.

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