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Old 10-16-10, 08:11 PM   #1
mcnuggets
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Chain is rubbing on spokes on fixed gear

I am running a Paul High Flange Hub paired with a SRAM Omnium on an IRO Mark V. The chain is rubbing very slightly onto the adjacent spokes when riding on the fixed side. Enough to create a noise. The cog appears to be true. How do I remedy this? Try on a different 1/2x1/4" chain and see if it is slightly thinner? Are there any spacers I can use to edge it out?

Thank you for you help.
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Old 10-16-10, 08:16 PM   #2
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Yes I would use a bottom bracket spacer from lbs. You want your chain to be fairly straight front to back and this will help the chain line. Good luck
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Old 10-16-10, 08:27 PM   #3
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The chainring seems to be slightly further out than the cog. I don't think a spacer would help in this case. It isn't off enough, IMO, to make too much of a difference. Less than 4mm from what it looks like. The cog is just a smidgen too close to the spokes from what I see. If the cog itself can be spaced further out, less than 0.5mm, that would be enough. The chain, in certain sections, 'clicks' against the spoke. This is my impression at least because the black coating of the spoke is wearing off. The clicking is not continuous when the wheel is spun and only happens at certain sections of the chain.

Last edited by mcnuggets; 10-16-10 at 09:27 PM. Reason: clarified post
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Old 10-16-10, 09:47 PM   #4
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check the dish.
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Old 10-16-10, 09:52 PM   #5
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you could also put a washer between the freewheel and the hub body. unfortunately, it seems that yor wheel's been improperly dished. oops. stilll, you can space out the freewheel about a mm with no problem.

-rob
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Old 10-16-10, 11:48 PM   #6
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No amount of dish error could ever cause a chain to rub on spokes, given that it has to run past the rim. The simple answer is that your sprocket is too close to the hubs flange.

You could use a spacer between the sprocket and shoulder of the hub, but I've never known a fixed sprocket to need one. Is it possible that you have a shouldered sprocket mounted backwards, that is with the shoulder out?
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Old 10-17-10, 12:56 AM   #7
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I'm pretty sure that nwbikeman meant for you to put the BB spacer behind the rear cog and not to put it on the BB. If the chain is far enough in with the fixed cog to rub on the spokes then it's highly likely that spacing the REAR cog out with a BB spacer would aid in straightening the chain line.
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Old 10-17-10, 01:26 AM   #8
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You sure you don't have the cog on backwards? They usually have a shoulder on one side in order to get enough threads. This shoulder should be facing the spokes to space the cog far enough away from the spokes so it doesn't rub.

This side faces the spokes:


This side faces to the outside:



Also, why are you using a 420 motorcycle-chain on your bike? The correct size is 1/2x1/8", or about 1/2 the width of your existing chain.

These are 420 (1/2x1/4") motorcycle chains:



These are 1/2x1/8" bicycle chains:



Last edited by DannoXYZ; 10-17-10 at 01:34 AM.
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Old 10-17-10, 01:50 AM   #9
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What cog are you using? Some cogs have taller shoulder than others, and switching to a taller one might do the trick.

Refer to Sheldon Brown's chart for more info on cog thickness.
http://www.sheldonbrown.com/chainline.html#chainline1

Also, switching to a thinner chain would require you to change your chainring and/or cog.

Last edited by Squirrelli; 10-17-10 at 01:59 AM.
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Old 10-17-10, 10:27 AM   #10
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after all that , consider a 3/32" thick cog and chain, and perhaps a mm thick shim behind the cog ..
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