Regular SON dynamo hubs come with a hex key skewer rather than a QR. That's not a big deal, but it's probably simpler for the other 2 riders on the household who are running these hubs to deal with a QR skewer, since it's easier for them to get a feel for a tight QR than for "8-10 Nm" on the hex key, especially using a crank brothers multitool by the side of the road.

I haven't seen any admonition not to use a QR, and I doubt they could get a QR cam to put more tension on the skewer than 10 Nm on the hex skewer would pull, but I'm not sure.

I'm wondering if the hex skewer is supposed to just be a security thing, since it requires a thief to have a 5mm hex head rather than just fingers. I'm not sure that's much in the way of security. I did get some pentagonal key skewers that would provide more security, since few people are carrying one of those around, but at present these bikes don't get out of anyone's sight.

  • Is it actually a skewer? Isn't it a thru axle? I have two thru axles, one with a 6mm hex head and one with a handle. The one with a hex head needs less retightening and one is much more certain it is tightened with the right torque. – Vladimir F Jan 23 at 20:10
  • There are SON Dynamos that come with security QR axels. I've had them, but don't have one on hand now. You should be able to replace with a QR. Just thread it all the way out an replace. It'll be fine. – Paul H Jan 23 at 21:38
  • Mine are all regular 100mm OLD fronts with 9mm axles and hex head skewers. I figured it would probably be OK -- and the instructions say something about a QR, so I figured maybe they supplied some that way. – WPNoviceCoder Jan 24 at 1:15

Yes, they don't care, you can use any QR you want. I've used an early SON28 with the stock one, a Pitlock, an external cam light skewer, and various Shimano skewers, and a current SONdelux with the stock one and a Shimano QR. It doesn't matter.

I don't know the numbers but I believe internal cam skewers develop quite a bit more clamping force than bolt-down skewers, so in other words it's conceivable to make a hub that could care about this distinction. But Schmidt hubs don't.

  • That was my suspicion. Thanks for confirming. As for axial clamping force, I can't find a good source on what QRs generate. Using a torque to axial-force calculator for a 5mm skewer, a 0.2 guestimate for friction (steel on aluminum) and 7.5 N-m torque as specced by SON, that comes to 7,500 newtons for the clamping force. – WPNoviceCoder Jan 26 at 14:45
  • @WPNoviceCoder You can take a basic adjustable cone hub with a standard axle and test the different ones for their effect on bearing preload. I believe what you find is internal cams do the most by a lot, and external cams and bolt-down skewers are somewhere in the same vicinity. – Nathan Knutson Jan 26 at 19:31
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    Good idea. I always make the preload tension on my cup and cones have just a bit of play, so they have none when tensioned with the QR. I could at least see what the torque reading looks like when I reach the spot where that little bit of wiggle disappears. – WPNoviceCoder Jan 27 at 16:46

Dynamo hubs provide a little bit of resistance. Lights on, it's 6 watts. You are probably pedaling the bicycle forwards at 100 watts. When braking, at 25 km/h (6.94 m/s), a 100kg rider + bike with 0.5 g braking force requires 3400 watts to brake.

So even though the SON dynamo hub is "braking" you all the time a bit, its braking power is about 0.18% of the power a real brake needs.

Go ahead and use a QR skewer. However, for this you need an axle that supports using QR skewers. I'm not sure if all SON models have the hollow QR axle.

However, internal gear hubs and hub brakes (apart from disc brake that has a caliper attached to the frame or fork) require some separate mechanism to apply the reaction torque to the frame or fork.

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