Downhill Race

From: Ilan Vardi (
Date: Thu Apr 21 2005 - 00:12:15 PDT

Hello, I read your article about rolling cylinders and have a comment
on your final comment regarding "mag wheels." First off, the word "mag"
is short for magnesium, which is part of the alloy making the wheels
lighter than steel. Secondly, your entire experiment (distribution of mass)
is relevant to such wheels, since you may have noted that high end car wheels
have much bigger rims, and much thinner tires, in the sense that more of the rim/tire
combination is taken up by the rim (actually, the tires are wider, in the sense
of cylinder height, than usual for better road grip in turns). Your experiment shows
that the reason for this must be that the rim alloy weighs less than the tire rubber,
which one may not have suspected otherwise. In particular, it is most important
to reduce rotating weight at the outside of the wheel, that is, reduce the
amount of heavier tire.

Well, I hope this will help convey some California car culture to the Exploratorium.


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