Daniel Boone Cycles, Inc - The Flying Wheel.

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Does "hard anodizing" make rims stronger?

Jobst Brandt:


There are several kinds of dark coatings sold on rims. Each suggests that added strength is achieved by this surface treatment while in fact no useful effects other than aesthetic results are achieved. The colored rims just cost more as do the cosmetically anodized ones. The hard anodized rims do not get stronger even though they have a hard crust. The anodized crust is brittle and porous and crazes around spoke holes when the sockets are riveted into the rim. These cracks grow and ultimately cause break-outs if the wheel is subjected to moderate loads over time.

There is substantial data on this and many shops that build many wheels, can tell you that for instance, no MA-2 rims have cracked while MA-40 rims fail often. These are otherwise identical rims.

Hard anodizing is also a thermal and electrical insulator. Because heat is generated in the brake pads and not the rim, braking energy must cross the interface to be dissipated in the rim. Anodizing, although relatively thin, impedes this heat transfer and reduces braking efficiency by overheating the brake pad surfaces. Fortunately, in wet weather, road grit wears off the sidewall anodizing and leaves a messy looking rim with better braking.

Anodizing has nothing to do with heat treatment and does not strengthen rims. To make up for that, it costs more.


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