"Dave Plowman (News)" wrote in message
...
In article ,
Jeff wrote:
No. Once yopu put a non circular tyre on, you vannot talk about radius.

The only distance that matters is the distance between the axle and
the road. That is what determines the rotation rate of the wheel.

Yes, it is better not to call that the radius.

Radius between centre of wheel and point of contact to the road surface.
That is the only relevant part as regards how far the car travels per
rotation of the wheel. Not any theoretical amount.

Yes, but you also have a problem with explaining why it isn't the
circumference of the tyre which doesn’t change much isnt what
determines the rotation rate of the wheel.