marcus.e.helman@gm.com wrote:
> I know it is common wisdom that clamping a wheel into a frame with a QR
> affects the adjustment of the bearings, causing them to move inward, and
> perhaps bind. Is there any proof of this? I find it kind of hard to
> believe. Is the idea that the axle compresses? I would have thought that
> a relatively short piece of steel would not respond to force this way. If
> it is not axle compression, what accounts for this supposed phenomenon?
>
> If axles are in fact this flexible, wouldn't we observe the opposite effect
> with bolt-on wheels? It seems to me that tightening the nuts on bolt-on
> wheels would essentially be stretching the axle. I have never heard that
> track axles should be adjusted to bind just a bit because tightening the
> nuts would cause the wheel to loosen up.
Well, it's not flexibility, but compressibility. The reason you don't see a change with bolt on hubs is that the stretching occurs independently on each side because each locknut provides its own tension. The stretching therefore only takes place between the axle nut on the outside of the dropout and the locknut on the inside of the dropout; IOW, only the few millimeters under the dropout on each side is stretched.
With a QR, the pressure is applied simultaneously to the outer face of each dropout, which in turn compresses the entire axle via each locknut.
--
-John Thompson (john@os2.dhs.org)
Appleton WI USA