The sled moves under the car. When the sled is under the car the fingers extend under the wheels. They do not, cannot, extend under the part of the wheel that is in contact with the ground. But they can, and do, extend to the parts of the wheel that are close to the ground. Again, look at 1:12. You can see the prongs go around the wheel, not directly underneath it.
You can see the prongs go around the wheel, not directly underneath it.
The videos linked to by improbable22 make it easier to see this.
My (very limited) understanding of radial tires (or at least steel belted ones) is that it would be bad to stress the tires in that manner for long periods of time. But lifting the car by the tires this way for a few minutes should be OK?
It would be interesting to learn what tire manufacturers feel about this. (Of course they probably would want to disclaim liability because there's no reason for them to want to bless this).
The sled moves under the car. When the sled is under the car the fingers extend under the wheels. They do not, cannot, extend under the part of the wheel that is in contact with the ground. But they can, and do, extend to the parts of the wheel that are close to the ground. Again, look at 1:12. You can see the prongs go around the wheel, not directly underneath it.