Powerful mid drive rear wheel build

[12-C]

Looking to rebuild the rear.

My concern is the torque that can be put through the rear in low gear.

I'm considering using a onyx rear hub.

How many spokes would be best?
More thinner spokes or fewer thicker spokes.
From what I've gathered, thicker spokes although stronger can not necessiarly reach their proper yield properties without actually damaging the rim/nipple and will get a spoke that might be too loose and and face other problems down the road.

What gauge spokes?

What lacing patterns?

 

[Balmorhea]

14-15ga (2.0/1.8mm) is usually best. Good balance of reliability and ease of construction/maintenance. A quality hub like Onyx will not be drilled for thicker spokes than 14ga. For a hub with lots of offset (8/9/10/11/12 speed on 135mm), it’s a good idea to use thinner spokes, like 14-17ga (2.0/1.5mm) on the left (looser) side.

The torque your motor makes is no big deal at all to your spokes. The freewheel ratchet and parts of your mid drive will break long before the wheel becomes stressed from torque. Remember it’s getting divided among 32 or 36 spokes, so no single spoke has to work hard to carry the torque. Spokes should be pretensioned to at least 1000 newtons each (about 225 pounds) on the tighter side of the wheel, so the change in tension resulting from wheel torque will not be a large percentage of this value.

More spokes are better than fewer, always— but many of the best rims are not available in 48, 40, or even 36 holes anymore. So if you can get a stronger rim in 32 hole than in 36 hole, it may be a better choice.

For 32 or 36 spoke hubs, cross-3 lacing is customary and appropriate if the flange diameter is less than about 80mm. For bigger flanges, fewer crossings.

If you’re intending to use more than about 1000W of motor power, or smaller than a 42t chainring, your bike’s gears and chain will suffer far more wear and breakage than the spokes of the wheel. Have a plan for that. Mine would involve using 7- or 8-speed cassettes and chains to keep down the cost of frequent replacements.

I would also avoid the expensive and unique Onyx hub in favor of a nothing-special Shimano hub that has a cost-effective, well proven, and widely available freehub body. You will probably wear out the freehub in due course, so get one that’s not unduly difficult or expensive to replace as often as necessary.

 

[12-C]

Thanks for the great info!