Tuesday, July 28, 2009

Hubs

Recently, Pardo and I found a click-click-click noise in my 3.5 year Shimano DuraAce 7700 freehub. While it was well past the warranty period, this wheel had only about 10000 miles on it, and was never ridden in the rain, so while we took it apart, overhauled it, immersed the freehub driver in bio-diesel, and re-lubricated everything, we discussed what other hubs would have lower maintenance but still remain relatively light.

The lowest maintenance hubs out there are probably the Phil Wood FSA hubs. As Pardo says, "Cheap, durable, light, pick any two. Oh wait, the Phils are just durable. They're expensive and heavy." But nothing beats Phils for durability --- I bought a pair in 1993, rode them for 10 years or so, and sold them in 2005 for $10 less than what I paid for them. Yes, there's inflation, etc., involved, but still, that's pretty darn good.

Then we looked at another important factor, which is the rear hub flange spacing. To check out the numbers, download Spocalc, and try playing with wR on the rear hub. Then observe how the difference between left and right spoke tensions change as you increase or decrease the distance the right flange is from the center of the axle. A decrease from 20mm to 16mm (just 4mm) results in the right side tension dropping from about 75% of the left side tension to 50%. That's almost 30% loss in strength, which is directly related to the total tension in the spokes on the wheel. (You have less overall tension in the wheel when you can't tighten up the right side spokes)

So we took a survey of various hubs using information we could find online (these are all 130mm cassette hubs):







Hub wR (mm)
Shimano 7700 21.1
Shimano 780020.55
Phil Wood Touring18
Chris King18.5
White Industries H218
DT Swiss 240s 17
Campy Record 200715.2

Yes, for wheel strength, Shimano rules, and Campagnolo sucks. This is by design --- Campagnolo designed their cassettes to require more space on the right side of the hub, which meant that for any given model of hub, the Campy version of the hub is weaker than the Shimano version. But you can see when it comes to actual hub implementation, nobody can touch Shimano. A wheel built using the Campagnolo hub is weaker than one using the same hub and spokes and built using either of the Shimano hubs listed here. (Note that there's quite a bit of variation among Shimano hubs, so it's not enough to just use a Shimano hub, you have to use a good one)

No, this doesn't mean that non-Shimano hubs completely suck. If you build with off-center rims (OC), they help you regain some of that lost strength, which means that it doesn't matter as much that your hubs' right flange isn't optimal (in fact, if you're running Campy wheels, you have to run OC rims to have any wheel strength at all). On the other hand, you can build with a Shimano hub and an OC rim, and that'll be even stronger! In exchange, however, you do have to overhaul Shimano hubs every 5000 miles or so, and until the 7900 debut, you have to deal with cone wrenches and hub pre-load adjustment, which I consider a major pain in the neck! I haven't seen the 7900s yet, so I don't know how much of the "you no longer need cone wrenches" part is marketing.

On the plus side, Shimano hubs do look pretty good, roll nice and smoothly when properly maintained, and have a very quiet ratchet (I'm do like how quiet the freehub is --- you can barely hear it if you're rolling along in a quiet neighborhood).

Obviously, even Shimano hubs can be badly built into wheels, so ultimately good wheel-building technique still trumps all, but given how much time it takes to build a good wheel, you might as well start with the hub that gives you the best results given your effort.
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