"Tim Streater" wrote in message
.. .
In article , Huge
wrote:

On 2018-06-25, Andy Burns wrote:
Huge wrote:

Andy Burns wrote:

there isn't a single distance from the centre of the axle to all
parts of the tyre in contact with the road ... the average distance
perhaps?

This is really, really simple. Why are you all making it so
complicated? (It's the *shortest* distance, obviously. Just draw a
bloody
diagram.)

The diagram I linked to yesterday seems suitable

http://the-contact-patch.com/book/road/c2020-the-contact-patch#figure-ERr

Because it's wrong. In this context, the relevant dimension is O - Q. How
could it be otherwise?

One revolution of the wheel has to equal one passage of the tire's
circumference along the road (since the tire does not slip around the
rim and assuming no slip on the road). How could it be otherwise?

Talk of "effective radius" is not relevant.

Yes it is when that is what determines the rotation rate of the wheel
as can be seen with different diameter wheels with no tyre.