I think they misspoke when they said "in" the wheel, but supercars can have a separate motor for each wheel, and the closer they are to the wheel the better the torque as it's not also driving a longer shaft. The smaller the motor, the closer you can get.

▲

ErroneousBosh 3 days ago | parent | next [-]

I guess if you can make the motor and a suitable reduction box lighter than the equivalent bearing and driveshaft combination you could make the suspension arms mechanically simpler.

By using motors at each wheel you'd eliminate the need for a differential, saving a good 40-50kg or so. Of course, if you kept the drive shafts and put the motor and reduction box in the middle, you'd be able to use inboard brakes and save a lot of unsprung weight!

▲

ehnto 3 days ago | parent | next [-]

I wonder if that would be legal, or if there is a regulation about where you can put your brakes?

▲

ErroneousBosh 3 days ago | parent | next [-]

There are cars with inboard brakes, although not recently. From a packaging point of view putting them out at the wheel makes sense, since there's a lot of space you're not using otherwise.

It's hard to fit inboard brakes to front wheel drive cars because there's so little space but Citroën managed it with the 2CV and various derivatives, and the GS/GSA/Birotor family. They had an inline engine with a very compact gearbox behind, with the brake discs (drums, on very early 2CVs) right on the side of the gearbox.

You got lower unsprung weight and possibly more usefully the kingpin was aligned with the centre of the tyre, so when you steered the tyre turned "on the spot" rather than rotating through a curve.

Some old Jags and Alfas had inboard discs on the rear axle, which was of course rear wheel drive. They were a bit of a pain to get at.

	▲	avn2109 3 days ago \| parent [-]
		Super pro comment, should be much higher.

▲

amluto 3 days ago | parent | prev [-]

I’ve generally assumed that brakes are in the wheel because they’re not all that massive, they get decent cooling airflow in the wheel, and they can produce enormous amounts of torque.

▲

adgjlsfhk1 3 days ago | parent | prev [-]

it would be really interesting if it became possible to do electronic only breaks. I'm sure the regulatory system isn't there yet, but it would let you shave a whole bunch more parts and complexity

▲

jama211 3 days ago | parent | prev [-]

Interesting! But yes in axel in this case then