"The Natural Philosopher" wrote in message
news
On 24/06/18 22:18, Jeff wrote:


And yet if you consider a solid wheel, no tyre, it is the distance
between the axle and the road that determines the rate at which
it rotates at the same speed of the car over the ground.

Yes.

So when
a wheel with tyre sees a reduction in the distance between the
axle and the road due to a lower pressure in the tyre, you get
the same change in the rotation rate of the wheel which is
easy to measure with the ABS sensor on that wheel.

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.

What counts is the distance round whatever shape the tread is.

No, what matters is the distance between the axle and the road
as you agreed with the first paragraph of mine.

Al;l of
that has to be in contact with the road during one wheel revolution unelss
the tyre slips on the rim

Yes, but that isn't what determines the rotation rate of the wheel
that the ABS sensor is measuring.