Technical FAQ: Saving freehubs, aero is everywhere

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Dear Lennard, I’ve destroyed every aluminum freehub I’ve ever ridden (see attached photo). I gouge the cassette into the hub so far I sometimes can’t get it removed to replace worn gears without filing off metal chips.

Is this a regular issue for other riders? How do you prevent this kind of wear?

I know that steel freehub bodies don’t have this issue, since the harder metal doesn’t deform against the cassette, but most road wheels (especially nice ones) don’t use steel freehubs.

Any maintenance and purchasing advice would be very appreciated.— Ken

Dear Ken, Well, the tearing-up of the splines and the difficulty of removing the cogs are as sure as death and taxes if you’re a powerful rider using an aluminum freehub body that is Shimano/SRAM compatible and you’re using separate cogs. The problem is, besides the soft material, that the splines are so low.

It’s hard to imagine one of those cogs being able to plow completely through the wide, indexing spline on the freehub, but I have seen complete spline failure on steel freehub bodies that have, in the interest of weight savings, removed the centers of the splines, leaving thin, separated strips of steel. The circumstance was similar: separate steel cogs pushing into the splines, but in this case they kept going until they tore right through all of the splines and just spun freely on the freehub body.

The cheapest way to eliminate the problem is to not pedal hard; this doesn’t happen to 100-pound riders. But you probably don’t want to do that, so here are two more expensive options that will allow you to pedal as hard as you want.

1. Use a SRAM Powerdome cassette. The only engagement of the 10 largest cogs with the cassette is the set of splines on the largest cog, and those are aluminum and won’t damage your freehub body in the least. Check out the photo from the back side on the link. The first cog also has splines, but you’re generally too torque-limited to get that one to dig into the freehub body anyway, and even if it did dig in, you could still remove it easily.

2. Use a Campagnolo freehub body and cassette. The splines are much deeper on Campy freehub bodies, so the pressure is distributed more, and the cogs don’t tend dig into them. If you’re using an 11-speed drivetrain, a Campy wheel is interchangeable with a SRAM or Shimano wheel, generally without derailleur readjustment, because the spacing between cogs is the same with 11-speed cassettes from any of the three brands.

If you’re going to use a Shimano cassette, get one that has the most cogs riveted to aluminum carriers. This would be Dura-Ace, and the largest five cogs will be integrated onto two aluminum carriers; this guarantees that at least the innermost five cogs won’t dig into the freehub body. But judging by your 11-speed freehub body, it looks like only the smallest six cogs have dug into it. Low-end Shimano cassettes have (or at least had) three long, thin bolts holding the entire cog stack together, which should eliminate this problem, but I don’t believe this exists in 11-speed form.

There was a brief time in the 10-speed era when …

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