In article . com,
"41" wrote:

wrote:
On Mar 23, 4:30 pm, "41" wrote:

There should be very little discrepancy in suspension losses
between different tire models of qualitatively similar design at
the same width and the same pressure, since it is the air volume
inside them that does the bulk of the bouncing and the shock
absorbing.

I think the above is indeed the core issue, but I'm unconvinced
that the variables are well understood. Do we really understand
the r oles that the casing and tread play?

Sure. Deflate the tire, and press or rap it in and out. How much
shock does it absorb, compared to when inflated?

That's only one parameter of the effects of the casing and the tread, of
course. The classic issue in rolling resistance is hysteresis- which
did seem to be the major- although certainly not only- factor in the
ordinal rankings of the tires in the original BQ test.

Thus the road surface was smooth enough that suspension losses
are doubtful as the explanation for whatever minor disc repancies
from the drum tests might have been observed.

I'm not sure I fo llow how you've arrived at the above conclusion,
whether or not it's correct.

I mean, they found inflation pressure to not affect the results.

That's an incorrect representation of the findings. What they found was
that inflation pressure did not affect rolling resistance as much as
tire construction (casing type, rubber thickness, tread design). They
did not find that inflation did not affect the results.

If suspension losses were really important, pressure surely would
have had an effect. Remember that the theoretical calculation, which
does not include suspension losses, shows hardly any effect as well,
so it's not a matter of compensation hiding an effect.

There would be no "suspension losses" in steel drum RR tests, as the
drums are smooth and concentric. In addition to inflation pressure, one
would expect the stiffness of the casing and tread to be a factor in the
ability of the tire to absorb bumps.