Failed DT Swiss 240 Hub Flanges

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Failed flanges, front and rear DT Swiss/Hugi 240 hubs. From http://joeadnan.blogspot.com/2008/09/wheel-quest.html as of 2010/02.

Note: the hub model is not entirely clear. The above web page identifies them as DT Swiss 240, but on at least some years, the 240 flange closest the brake has through holes, while the 340 uses a solid flange. However, the hub pictures to show almost 1/2 revolution of a flange and just 6 spokes, suggesting a 28-spoke wheel, which is not available in the 340 series.

Service history and use unknown. There is no indication of the cause of the failure; it may have been the result of an accident rather than a hub problem.

A 28-spoke wheel may have higher spoke tension and higher tension excursions than a 32-spoke wheel, which would accellerate fatigue.

The cracked surfaces are not clearly visible, but the visible part of the rear crack is free of darkening typically associated with fatige failures.

The rear flange looks to have cracking on the periphery of the flange, near the failed spoke hole.

The lacing pattern is not clear. The front is clearly at least 2-cross, but is significantly away from tangent, which may indicate it is not 3-cross. Lacing that is more radial means spoke tension goes through a thinner part of the flange and thus tends to be more prone to flange failures.