So many misconceptions. I may as well show up and piss off everyone.
Hub motors are easy to fix flats on. Sure you have to deal with a torque arm, but only if you pull the wheel, which is almost never necessary. I include a short wrench in my tool kit and thats good enough for a roadside tire repair. But normally I don't want to work that hard. I leave the tire in place, try and find a shady spot on grass or against a wall out of the sun, then lay the bike down, unseat one bead only and pull the tube out the side. I won't describe the process of finding/patching the hole you all know that. After patching, I stuff the tube back into the still mounted tire, seat the bead and pump back up. Done for every kind of flat except the kind that makes me install a replacement tube, which I also carry because experienced bike commuter.
This was on a bike stand but I've done it countless times roadside. Hub motor, tube being repaired and wheel is still on the bike. This was a Slime Repair Saturday where I substituted slow-dribbling Slime holes for proper permanent patches. I use FlatOut Sportsman now which seals forever, dry.
What else?
Hub motors do not intrinsically require heavy spokes or rims. EVERY wheel build requires heavy rims if you are going to ride around at Class 3 speeds on pavement. I use double-wall fat rims, or carbon fiber deep dish, or on nonfat bikes I try and pick downhill rims like a DT FR560 (29er), or a Sun Ringle MTX39 (26") or Alienation Black Sheep (20"). I do these for hubs or mid drives in equal measure. As for spokes what you need are quality spokes. A strong rim is a flexible rim and using overly stiff spokes like straight, non-butted 12-gauge is going to create a rim that breaks rather than flexes thru a problem. My almost-8000-mile hub rims use quality butted DT Champion 2.0 spokes. Thats 13 gauge. My c/f fat rims: Sapim Strongs. Not the thicker E-Strong either. Now, if you are going with a 3kw+ QSV3 direct drive hub then sure do a moped rim and spokes on that 50 mph bike. But a Class 3 ebike? Build it with quality components and have at it. You'll be fine.
Worth noting: I had a low opinion of the Sondors 80mm single-wall rims with their 14 ga spokes, but being a mod on the FB user group has let me see that over the years they have almost zero wheel failures, even though they are selling the bigfoot full size 750w motors with 48v batteries and 25a controllers, with members back in the day commonly adding in 35a controllers and 52v batteries. I thought they'd be getting wobbly wheels right and left. It never happened. There being many many cycling noobs there has resulted in some issues for sure, but only a few.
And chains? Mid drives require a proper chain. Thats on the builder. KMC 'e' chains and job done. Or the SRAM 'e' chain. And yes they cost real money. Regardless, ALWAYS carry a spare chain and a couple quick links. You are rolling again in 10 minutes if you repair with your mini Park chainbreaker, or 2 minutes if you just put on a new one with a quick link.
But first and foremost - and this is unavoidable - if the rider learns how to ride a mid drive they never break things.
If you can ride a bicycle you already know how to ride a hub drive ebike. Not so a mid drive. Particularly a powerful one that can tear your chain apart. Fear not. The rules are simple.
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