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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.

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Old 06-23-10, 03:35 AM   #1
JeffThompson
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Can you re-round a rim if it's slightly off?

I have a rim i'm about to build and its "true" by the fact that it doesn't move from side to side at all.
BUT, it is A LITTLE ?un-round?(horrible grammar)
Is there any simple way to fix this?
I really like this rim and I dont think i'm gonna find another pair anytime soon.
It's a Mavic g40 Module E 27" 1 and 1/4 rim.
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Old 06-23-10, 04:03 AM   #2
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If your rim is D-shaped, it's going to be tough.
If the rim is fine, but it's out-of-round, it can be fixed through spoke adjustment. But you need to know what you're doing here.
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Old 06-23-10, 04:29 AM   #3
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It's barely off maybe 2-3 mm....
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Old 06-23-10, 04:34 AM   #4
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It sounds to me like you're talking about radial truing. Its possible that a rim could be bent out of shape though, particularly if you know that it became "un-round" after a crash or a big hit, in which case the solution may not be so easy. Check out this link: http://www.parktool.com/repair/readhowto.asp?id=81
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Old 06-23-10, 05:04 AM   #5
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Originally Posted by WillJL View Post
It sounds to me like you're talking about radial truing. Its possible that a rim could be bent out of shape though, particularly if you know that it became "un-round" after a crash or a big hit, in which case the solution may not be so easy. Check out this link: http://www.parktool.com/repair/readhowto.asp?id=81
Its not very bad at all. So if i took it to a bike shop after lacing it, they would be able to kinda kink it out?
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Old 06-23-10, 05:09 AM   #6
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Its not from a crash either. its barely noticeable when you look at it spinning....maybe i could tension the spokes hard enough to bend it back before I cut out the hub and lace it again?
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Old 06-23-10, 05:32 AM   #7
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It hasn't affected the ride from what ive noticed so far. I just want to know if its possible.
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Old 06-23-10, 08:22 AM   #8
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It is possible to hammer in/out the 2-3 mm flat spot if you unlaced the wheel. Use a rubber mallet. Get it round to within 1 mm in the free state, then re-lace.
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Old 06-23-10, 08:45 AM   #9
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It is possible to hammer in/out the 2-3 mm flat spot if you unlaced the wheel. Use a rubber mallet. Get it round to within 1 mm in the free state, then re-lace.
I fixed a flat spot by taking out about six spokes at the flat site and then used a rubber mallet on it. That worked great, no more hop and can't even find it
any more.
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Old 06-23-10, 08:58 AM   #10
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Originally Posted by JeffThompson View Post
I have a rim i'm about to build and its "true" by the fact that it doesn't move from side to side at all.
BUT, it is A LITTLE ?un-round?(horrible grammar)
Is there any simple way to fix this?
I really like this rim and I dont think i'm gonna find another pair anytime soon.
It's a Mavic g40 Module E 27" 1 and 1/4 rim.
Before we all take off into the yonder with suggestions, I need to clarify some things. "..rim I'm about to build.." sounds like it is not laced currently, but then how would you know "...it doesn't move side to side.."? Do you mean rebuild?

If it's not laced how do you know it's out of round? Did you measure the diameter at multiple points? If so 2-3 mm out of round is only a variation of 1-1.5 mm from center, which I don't like but is not terrible.

If it is laced we know nothing of the actual condition of the bare rim, and thus whether it is worth rebuilding, unless you manage to get all the spokes to equal tension, which is a bit of a challenge.

In either case you did not specify in which direction it is out of round. If a flat spot and not caused by too much spoke tension you would indeed need to physically move it, but you must do so carefully or you may create high spots on either side. If a high spot then odds are extremely high that spoke tension is incorrect. On a laced wheel I would not consider a deviation of 2-3mm in round "minor."

Last edited by cny-bikeman; 06-23-10 at 09:02 AM.
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Old 06-23-10, 10:16 PM   #11
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Yeah, I missed the part about "rim I'm about to build". Sorry, my advice about radial truing is of no help.
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Old 06-24-10, 02:53 AM   #12
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Originally Posted by cny-bikeman View Post
Before we all take off into the yonder with suggestions, I need to clarify some things. "..rim I'm about to build.." sounds like it is not laced currently, but then how would you know "...it doesn't move side to side.."? Do you mean rebuild?

If it's not laced how do you know it's out of round? Did you measure the diameter at multiple points? If so 2-3 mm out of round is only a variation of 1-1.5 mm from center, which I don't like but is not terrible.

If it is laced we know nothing of the actual condition of the bare rim, and thus whether it is worth rebuilding, unless you manage to get all the spokes to equal tension, which is a bit of a challenge.

In either case you did not specify in which direction it is out of round. If a flat spot and not caused by too much spoke tension you would indeed need to physically move it, but you must do so carefully or you may create high spots on either side. If a high spot then odds are extremely high that spoke tension is incorrect. On a laced wheel I would not consider a deviation of 2-3mm in round "minor."

I said about to build because it's still laced to shimano 600 hubs that i had.
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