[exabrial]

There's a concept called "unsprung mass", which basically destroys handling of all vehicles from race cars to trucks. Basically the greater the unsprung mass, the harder it is to damp the input into the suspension because of the inertia of the moving suspension components themselves. An ideal suspension has zero undamped mass, and all input to the suspension is a direct result of contact with the surface the vehicle is traveling on.

There is zero chance this tech will make it into sports cars unless it can beat the weight of a magnesium or AL alloy rim. Even casual vehicles like minivans have rim weight minimized for comfort.

Not an expert :) just watched enough Donut media on youtubes :P

[JumpCrisscross]

“The unsprung mass (colloquially unsprung weight) of a vehicle is the mass of the suspension, wheels or tracks (as applicable), and other components directly connected to them. This contrasts with the sprung mass (or weight) supported by the suspension, which includes the body and other components within or attached to it. Components of the unsprung mass include the wheel axles, wheel bearings, wheel hubs, tires, and a portion of the weight of driveshafts, springs, shock absorbers, and suspension links.

…

The unsprung mass of a typical wheel/tire combination represents a trade-off between the pair's bump-absorbing/road-tracking ability and vibration isolation.“

https://en.m.wikipedia.org/wiki/Unsprung_mass

[westmeal]

One thing to add, while your wheels and tires are a big chunk of the weight here - you also have the uprights/knuckle and the wheel hub, bearing, brakes, rotor etc etc. All of that adds up quick. Most times if you are looking to reduce this on a car you will have the most gains (or losses haha) switching to an aftermarket wheel. No wonder the manufacturers slapped alloys on their cars too!

[Neywiny]

There's also the inertia problem where it's harder to accelerate mass that's further away from you. The classic spinning ice skater demo. This feels physically disadvantageous. Hopefully I'm wrong though, the more competition in spaces the better.

[usrusr]

But here that mass is the driving force: the further away from the center you put your magnets, the less force (the less magnet) you need for a given amount of Newtonmeters. When you move that mass away from the center, you need less mass, changing at the same factor as rotational inertia changes. So no improvement or drawback in terms of rotational inertia, but improvement in terms of total mass (and improvement in terms of unsprung mass when comparing to a wheel motor in the hub).

In a way this is a transfer of semiconductor miniaturization to motors: when your power transistors can switch fast enough, you can replace fewer bigger coils with more smaller coils (that switch more often per rotation) and moving it all rimward gives you more torque per Newton. That ice skater effect? It's on your side.