[johnwalkr]

I think it still needs the wheel, and all the related parts in the middle like an upright/steering knuckle, which probably cancels out any mass of the motor that is acting as a structural part of a wheel. Other things like brakes would still be required. These should allow for regenerative braking normally the braking torque of a motor is nowhere near the acceleration torque, plus they don't mention braking function anywhere so it's safe to assume there's no special performance there. In all, I would assume for now that a 40kg motor would add approximately 40kg to the overall wheel mass, possibly even more. It would be interesting to see if there's a concept for an inboard version of these motors and compare to others.