Weight Weenies

goodboyr wrote:

TheDarkInstall wrote:

goodboyr wrote:Can you give an example of one?

An example of one what? A hub where QR force doesn't affect bearing preload?

Extralite CyberRear SP.


The arrangement has the locating bearing in the outside end of the freebody, then 3 more bearings spaced out across the freebody and hub shell. The opposite non-locating bearing has a preload adjuster sitting against it. The axle end have nothing at all to do with the preload on the bearings, and you can clamp the hub in as hard as you like (within reason, of course!) and the bearings won't be affected, as all you are doing is putting force down each end of the axle.

The manual for these hubs says that to adjust preload properly, the hub must first be properly clamped with appropriate qr force in drop outs.

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Yes, but this is not because QR force affects it. It is because to get the absolute correct preload, you need to spin the wheel and observe how smoothly it comes to a stop, when in the bike. Turning the axle with your fingers with the wheel out the bike can not show this.

Aha. Makes sense. Thxs.

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Yeah it is a pretty cool system they use.

There are a few issues with the hub that require a decent level of mechanical skill to sort out, but that is for a different thread.

Other hubs;

Tune Mag170

QR force does not affect preload. The end caps on the axle bottom out with around 1mm gap on the freebody end, which is taken up by washers. QR force would affect preload if too many washers were used, but that would be incorrect setup, and therefore not by design.

uncle-gee wrote:dt240s ->mavic ksyrium -> cartridge bearings preload and QR tension affects the bearings

I don't have a Mavic wheel (anymore) to test this with, but I am not sure this is entirely correct. Can anyone test this? You would need t clamp your wheel into the drops, dial the preload until the wheel spins slowly, then undo the QR and spin it again in the drops to see if the spinning is any looser...

goodboyr wrote:dt240 do not have adjustable preload, but similar to older zipp hubs, rely on tolerances and a certain amount of qr tension to get preload right, so I disagree that qr tension has no effect.

Again, I can't test this myself as I don't have one of these hubs at the moment, but I would like to know more about this.

One thing that does affect the bearings, is how straight the dropouts are. If one is at an angle to the other, and they are not perfectly parallel (Cannondale, you *f##k*...), then this will put a non-linear force on the inner race of the bearing, which will cause it spin slightly gyroscopically, which is essentially putting a bizarre modulating variety of preload through the bearing around every rotation. This has nothing to do with the QR tension, and to my knowledge has only ever been designed-away by one hub company (Gokiso), at the cost of a very heavy hub unit. In practice, the bearings in hubs get shagged up through general use anyway, and replaced fairly regularly, so this is not really a major issue, unless you are ultra anal about having nanoscopically accurate spinning profiles on all bearings with no discernable friction. In actual use, aerodynamics will play a much much bigger part in speed, so this isn't a biggie, but still could be dealt with through design (or actually making straight frames / doing post-mould machining to make straight)

/essay

/rant