On Sun, 24 Jun 2018 12:32:13 -0700 (PDT), wrote:

snip

Take a spare tyre. Wrap a tape measure around the circumference
along the centre of the tread area. Measure the circumference.
Place a plank through the tyre and stand on the ends. The tyre
will deform in a similar way to a deflated tyre on a wheel.
Re-measure the circumference. The air pressure will not have changed,
so if "pantographing" has taken place the circumference will be
significantly reduced and that change will be attributable purely
to such shape factors. If on the other hand the circumference is
not significantly altered then "pantographing" is not an important
factor.

Does that experiment seem valid?

It's sorta what you do when you accurately calibrate a cycle speedo.

You place the valve at the bottom and make a mark on the ground at
that point. Then with the tyre (of the wheel supporting the speedo
sensor) and with the right pressure in that wheel and with the bike
with it's typical load (so you and luggage etc), you wheel the bike
forward one turn of said wheel (valve at the bottom again) and then
measure the distance between those two points.

Now, presumably if it didn't matter about the load on the tyre they
would tell you to just put a tape measure round the outside of the
tyre?

When I built the kitcar I used the same process to determine the revs
/ m and so the speedo gearing, same on the electric motorbike I
designed, built and raced (and got an award from the IEEE for
'Technical innovation'). ;-)

Something to so with the sophisticated speedo I designed and built ...
weg

Cheers, T i m