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

The radius of the orange arc showing effective rolling radius is
inbetween the length of OQ and OP, what makes it "obvious" to you that
the shortest distance applies?