Freehub Hub Body Failure

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From http://roguemechanic.typepad.com/roguemechanic as of 2007/08/29 (originally dated 2007/05/03):

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Accompanying text says (in part):

[T]he first photo is the part of the hub that the freehub body is installed over. It's where the pawls are located (pawls and springs not shown in photo).

Separately, the same page reports (from 2006/05/25) that after a season or so of riding, the drivetrain got noisy and started skipping because the freehub body has side play. The image above shows two Mavic freehub bodies. The left has about a season of riding; the right is new. The used one has a thinner (worn) nylon bushing. Wear varies with use, including abrasive contaminants, maybe also corrosive contaminants, and varies with lubricant.

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A follow-up reports cyclingnews.com reviewed Mavic Ksyrium ES wheels and the author James Huang commented on the freehub body bushing. From http://www.cyclingnews.com/tech/?id=2006/reviews/mavic_ksyrium_es as of 2007/08/29 (dated 200/06/22):

Several years ago, Mavic replaced the inboard cartridge bearing of the original FTS freehub body in favor of a bushing in order to drop some weight with the newer FTS-L system. While this reduced the weight, it also sacrificed some long-term durability. Mavic's freehub internals are lubricated with fairly lightweight oil which should be replenished relatively frequently. On the old FTS system, running the pawls dry wouldn't signal the end of time, but the new FTS-L bushing rides directly on the hub shell and is much more prone to wear if the system isn't maintained properly. Riders in many parts of the world may not notice the issue, but those in more mountainous terrain where sustained coasting is more prevalent should pay heed and visit their local mechanic whenever they notice their rear hub sounding a bit dry and clackity.

As it turns out, a worn bushing necessitates replacing the entire freehub body [...] but if left unchecked for too long, the hub shell itself becomes worn and isn't nearly as easy to swap out as it requires sending the wheel back to the motherland for a rebuild. This is one area where a bit of additional mass would be most welcome.

From http://www.cyclingnews.com/tech.php?id=/photos/2006/tech/reviews/mavic_ksyrium_es/Mavic_freehub_bodies_old_vs_new as of 2007/08/29:

Mavics new FTS-L freehub body (on the right) dropped a chunk of weight over the old FTS body, but sadly, the smooth-running and lower maintenance sealed cartridge bearing was lost in the shuffle in favor of a lighter, but more temperamental, bushing.

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It is not obvious how bushing wear leads to the observed failure shown in the top photos -- it appears the bushing rides near to but not right on the failed spot. However, that is based on photos not direct examination, so it might be related.


See also FAIL-061.html