I've got my hands on an old dynamo hub, with a view to building a 700C dynamo front wheel for my hybrid. It uses (I believe, and will check) an M9 solid axle, but the existing one is QR. It certainly fits without being loose, but I don't have the nuts for it and it's built up with an ETRTO 590 rim at the moment so I wouldn't have any brakes for a test ride. I already use security QRs so I'm not bothered about having to undo nuts to take the wheel off.

Is there a reason to avoid doing this, or anything I should check before ordering parts?

  • QRs are a bit stealable, so nuts win there. Specially if you lock and leave it somewhere. – Criggie Dec 2 '19 at 18:43
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    @Criggie the current wheel has pinhead skewers, so track would actually be easier for a thief – Chris H Dec 2 '19 at 19:04

The only potential caveat is many solid axle hubs come with toothed axle nuts that are good at chewing up dropout surfaces, particularly aluminum or carbon. On "nice" bikes it's always best to just use track nuts if possible to preserve the frame while still getting good clamping force, or washers at the least.

  • Good point. This one had grippy washers under the "security" nuts that came off using mole grips (the donor was a scrapped rental-scheme bike via work). It's going on a 10-year-old aluminium hybrid, that while not worth much is very useful. Track nuts would be a good idea. – Chris H Dec 2 '19 at 9:22
  • My search for track nuts came up with nuts that are serrated as well. Hence I am a little at a loss here. Would you please clarify the difference between toothed axle nuts and track nuts? – gschenk Dec 2 '19 at 10:09
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    Track nuts have a serrated washer permanently attached. The serrations bite down but don't grind against the dropout as the nut is torqued, unlike a common cheap toothed axle nut, which make a mess of any dropout they touch but are well capable of destroying non-steel ones unless a washer is added. – Nathan Knutson Dec 3 '19 at 21:00

For less than $10 you could convert the axle to quick release. It is no more difficult than doing routine service. Purchase a replacement axle of the correct length and swap it out.

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    That's worth looking into. It may not be true in this case because as well as the dynamo there's a roller brake in there, so axles are likely to be a bit less ordinary. – Chris H Dec 2 '19 at 12:39
  • -1, no generator hubs use standard axles, and because an "old" one is what's being asked about specifically, your advice to disassemble it could result in demagnetization if it's something like a vintage Sturmey. – Nathan Knutson Dec 3 '19 at 21:05

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