I have a roval carbon wheel on specialized epic hard tail.

I want to install son dynamo hub on it.

I've seen it done on https://bikepacking.com/plan/lael-wilcox-2019-tour-divide-gear-list/ (SON 15mm thru-axle hub / Roval carbon rim)

Although I don't know the exact model of the hub or rim.

Is there a right size hub for wheels?
Searching for son 15mm thru-axle gives me two versions SON 28 15 and SON 28 15 110. Can I go with any of these two?

After installing hub, how do you put the wheel back?
Do you replace spokes with the right size and tighten it?

  • 2
    110mm is the newer front axle spacing Aka Boost. Chances are the Epic is Boost (unless its over 5 years old). The SON 28 15 hub is likely the old standard, 100mm.
    – mattnz
    Oct 12, 2020 at 2:42
  • How strong are these dynamo hubs? Will they withstand MTB usage?
    – MaplePanda
    Oct 12, 2020 at 6:15
  • 1
    @MaplePanda the bearings are as good as any normal hub, and the seals hold up well (I have one on a tourer, which I take over some fairly rough stuff; I've been hub-deep in water too). I'd be more concerned about the light level from a dynamo front light - mine is just about enough for potholed gravel tracks if I go slowly, though I normally turn on an additional light in that situation. Really rough stuff or overhanging branches and you'll need more power and a different pattern.
    – Chris H
    Oct 12, 2020 at 8:13
  • Its seems you are very unfamiliar with bicycle wheel building. It's not an easy process and you need specialized tools such as a wheel truing stand. You should find some articles and videos on the whole process to get a good overview of measurements, spoke selection, lacing and truing. Oct 12, 2020 at 14:13
  • @ArgentiApparatus yes I 'm not intending to do the wheel building myself. just wanted to know enough so that I can buy proper gears that match my bike.. Thanks!
    – eugene
    Oct 13, 2020 at 3:16

1 Answer 1


First you need to buy a hub which fits the axle type and dropout spacing of your bike. If you don't want to buy a new rim, you also need to buy a hub with the same number of spokes as your rim.

Once you have the hub, you need to measure the diameter of the spoke hole circles, and the flange spacings. You can try to get these dimensions from the hub documentation, but I always measure to be sure. You should be very skeptical of hub dimensions from unofficial sources or from online spoke length calculators. They are often wrong. You also need to know the "ERD" of your rim. You can measure or look it up.

Once you have the dimensions, you need to calculate what spoke length you need. You can use an online spoke length calculator, or use several and compare the results. You can buy custom spokes from many bike stores or on eBay.

Now with your new hub and spokes, you can disassemble the old wheel and build the new wheel, or you can have a bike shop do it.

  • Thanks for the answer There are tons of stuff I hear for the first time so the things I need to be careful of are.. 1. # of spokes 2. diameter of spoke holes 3. flange spacings 4. ERD of rim 5. axle type 6. dropout spacing At the moment, I can only make sense of # of spokes ... which of the above is about the 100 vs 110 width of the son 28 hub. (I thought they are related to somehow fork width.. )
    – eugene
    Oct 12, 2020 at 2:34
  • 1
    It is likely that a better solution is to leave the wheel intact, buy a dynamo wheel, and then either keep the original as a backup or sell it.
    – RLH
    Oct 12, 2020 at 3:01
  • I think that re-hubbing a carbon rim makes plenty of sense. The one thing I would add to the above is since generator hubs are big, you need to evaluate from scratch what cross pattern to use so as to avoid excessive bowing at the nipples. Any of the calculators that include a visualization of the angles will do this. Oct 12, 2020 at 4:26
  • @Nathan that's true of some dynamos but some are closer in size to normal hubs (I have a huge old Shimano on my hybrid but the SP-PD8 on my tourer is much smaller, as is the SON the OP is looking at)
    – Chris H
    Oct 12, 2020 at 8:08
  • I've twice done what @RLH suggested (actually the 2nd time I built the dynamo wheel myself, but that had more to do with a free dynamo hub and having picked up the skills already). Shopping around you can get a dynamo wheel for less than the cost of the parts
    – Chris H
    Oct 12, 2020 at 8:10

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