"Huge" wrote in message
...
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? I'm afraid this seems so obvious to me that I
cannot
find ways to explain it.

Yes, in Figure 6, I don't understand why the effective radius is not the
distance OQ. Or OP-z, if you prefer. I presume they are allowing for the
fact that the radius varies between maximum OP (at the edge of the contact
patch) and a minimum OQ (at the centre of the contact patch), and that the
effective radius is somewhere between the two and not the minimum OQ.