They started out at 100-profile but got lower with the evolution
of the tires. Many years ago, a tire manufacturers organisation
decided to do something about this so anything from 100 to 80
profile was normal profile and anything below 80 had to be in
the tire dimension. If everyone would measure an old spare tire
in 5.60-14 (no radials) you would come up with something close
to 24.5 inches as an average. Anything lower than 22.9 inches
would make it a low profile tire with 78 or lower aspect ratio.
Thomas
STAN CHERNOFF wrote:
> Bob,
>
> I don't think that any of the tires had a 100% aspect ratio but maybe they
> did?
>
> I took an empirical approach and did my check the old fashioned way. I
> used a 5.60-14 tire and a tape measure. The tire had a lot of tread left
> but was used and could have been a bit larger before. The tape measure
> said 77-3/32" for the circumference. I divided the circumference by pi and
> the result was 24.54 diameter.
>
> Stan
> =======
>
> >Now this tire stuff is making sense. Below, Thomas found a
> >cross reference from Michelin that lists the OD of our 5.60-14
> >as 628mm or 24.7". Since it is not a radial, the assumed 78%
> >is wrong. However, it is not 100% either or the final tire od
> >would be 5.6" x 100% x 2 + 14 = 25.2".
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