Spoke Bed Failure

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Sun "Zero Degree" 26"/MTB single-eyelet rim from a rear wheel.

There is a spoke bed crack at the eyelet on nearly every other spoke hole.

Three exaple cracks:

Used vigorously (racing) about 1 year/3,000km by 65kgf rider.

The wheel builder reports the wheel was built with "high" but not measured tension, and may have been overtensioned. However, "overtension" is hard to determine without a specification from the maker.

Note there are at least two limits to spoke tension: total rim compression (due to tension from all spokes together) and the rim's spoke bed strength at each spoke. Too much rim compression typically leads to a warped wheel. Stiffer rims, stronger rims, and rims with lighter spoke beds or certain alloys may fail at the spoke bed before the rim warps. Note that makers rarely specify recommended or maximum tension.