In message , Jeff
writes


"Chris Hogg" wrote in message
.. .
On Mon, 25 Jun 2018 15:50:06 +1000, "Jeff" wrote:



Yes, but it is the distance between the axle and the road
that determines the rotation rate.

If the length of the perimeter of the tyre is say 1.5 metres, and the
vehicle is travelling at 150 km/hr, that means the tyre rotates 100000
times per hour, or 1666.6 rpm, assuming no slippage between tyre and
road or tyre and rim. There's no getting around that, and there's no
mention of state of inflation, shape of the tyre or axle to road
distance.

Yes, but it is the distance between the axle and the road
that determines the rotation rate.

Why?

Long time since 'O' level maths but I suspect the relationship between
the radius and the perimeter only works for a perfect circle.


--
Tim Lamb