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I read bicycle rims wear out with braking. As the wear to the different areas of the rim is likely not equal as they are subject to varying brake force and duration, how would this affect wheel truing? Example, if wear at one area of rim is more than another area, the area with more wear would sit further away from the truing needle.

Is there an area of rim you are meant to use during truing, such as the edges?

Is there a part of the rim the brakes should be installed at?

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  • I don’t think this is a relevant factor. In any case: Close to the tire the brake track shouldn’t be worn since it’s very hard to get the brake pads there without touching the tire. You could set your needles there.
    – Michael
    Apr 28 at 5:44
  • I don't think it will matter. The difference in thickness between a new rim and a toast one will be a few 1/10s of a mm at most, so even if you wore exclusively on one side of the rim, by the time it was EOL, the rim would be pretty well banged up that the difference would be eclipsed by more ordinary bent-rim issues. Additionally, the side-to-side difference in when truing is measured with a dish stick, which won't be bothered by the extra-worn side. Apr 28 at 6:10
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    If rim-wear is so bad as to affect truing it may be bad enough to affect rim integrity and safety, too!
    – Carel
    Apr 28 at 11:13
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Wear will only vary around the circumference in rather odd cases, e.g. a significantly out of true wheel with brakes that don't self centre, damage, or local contamination reducing friction.

The two sides should wear evenly as well, as brakes rely on squeezing the pads against opposite sides. Here though, it would be possible to get some uneven wear. Perhaps chain oil on the drive side would reduce friction and wear, or one pad could get a piece of metal or grit embedded and grind down one side, but you should hear that and fix it even if you don't do much to care for the bike.

Radially, an old rim will eventually have a taper both due directly to wear on the braking surface (but not right at the bead) and indirectly as the worn rim is thinner and deforms due to tyre pressure. If you're truing such an old wheel to a really precise level, you'll need it to be good and round, and well centred, or you'll be measuring at different radii where wear is different. But if you're seeking real perfection from a well worn wheel, perhaps it's time to go shopping for a new one.

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