Bicycle Mechanics - Bent axle
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07-30-02, 07:12 PM
I put a new rear wheel on my soon-to-be-reborn cyclocross bike. It wasn't really a NEW wheel, per se, since I had it built up with a new rim and spokes and with an old hub from a wheel I trashed last year.
Settled completely in the dropouts, however, it's crooked. It diesn't wobble, it's just off the vertical axis by about 2.5-3mm at the rim [what is that, one or two degrees?]. At first, with horror, I thought it might be the frame, but the wheel is equally crooked on my other bikes, and other wheels seem straight in this frame.
Am I missing something, or is this, indeed, a bent axle? Does anyone know what is involved in getting a new axle for a Campy Daytona hub?
07-30-02, 07:17 PM
So the rim sits off to one side in the frame? Try turning it around so the freehub body is on the wrong side of the bike, and if it sits off to the opposite direction, then the wheel needs its dishing adjusted.
A bent axle is easy to diagnose -- hold the wheel, spin the axle by hand, and watch for wobbling on one side or the other. I tend to agree with the mis-dishing theory.
07-30-02, 07:52 PM
I considered the mis-dishing possibility. However, the wheel isn't just off to one side; the rim is actually crooked. At the top, it's to the left of the vertical axis by 2.5-3mm, and at the bottom, it's off by about the same amount to the right [measured inaccurately with a plumb bob from each of the chainstays].
07-30-02, 08:17 PM
That's odd. And the axle doesn't wobble when you turn it? And the wheel runs true?
The fact that the wheel sits at an angle seems to suggest that the wheel's axle is not fully seated in the dropouts. However, that's contradicted by your report that other wheels fit properly. :confused: Furthermore, you report that the wheel sits at an angle on other bikes too.
If the axle is bent and is causing this problem, then rotating the wheel's axle into different positions and clamping it into the frame should generate different angles. However, I'm with JohnE... it should be easy to see the axle wobbling when it's rotated. And those Campy axles are pretty strong (they have to be, with the driveside axle bearing so close to the center of the axle).
07-30-02, 08:23 PM
Aha, I thought of another possible reason for this: if the axle is straight but the bearings (or some of them) are the wrong size, or the wrong number of balls, or both. Has this hub ever been overhauled? The drive side uses a smaller bearing than the non-drive side, opening up the possiblility of someone mixing bearings by accident, or using the wrong size entirely, or the wrong size and also the wrong number of balls. This can make a wheel "orbit." If you clamp the wheel in, rotate it for a while and the angle changes, that would be support for this theory.
If you decide to take the hub apart, do it in a place where you can track down the pawl springs easily if they fly out of the hub and try to hide. :)
edit: If the hub giving you trouble is a Daytona, then the info I gave may not apply because they use a different bearing setup than the older Campy hubs I was thinking of. Sorry for the mistake! You can see an exploded view of the hub in Campy's documentation here (http://www.campagnolo.com/pdf/spares01-B.pdf) (requires Acrobat Reader, which can be downloaded for free if you don't have it).
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