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Old 06-10-2008, 01:27 PM   #106 (permalink)
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Originally Posted by CapriRacer View Post
Ah .... Mmmmmm .......Ah ........ Not exactly.

First, isn't this phrase contradictory? ....... "tall, skinny, short sidewall."

If you have tall, you don't have short sidewalls.

And this is certainly not true: ....... " Low aspect ratio tires have stiffer sidewalls = less RR."

Quite the opposite. Low aspect ratio tires have wider tread widths and that is the wrong direction for RR. Not to mention that lower aspect ratio tires generally have good grip - and that means poor RR. Contrary to popular belief, sidewall stiffness doesn't affect RR much.

BTW, based on the graphic we were discussing, you can't draw any conclusions. about aspect ratios - they are pretty mixed up in the data. Plus the lowest aspect ratio tested was a 60 series - and I don't know anyone who would call those a "Low Profile".
I was using a conclusion contained in the Finnish study of RR on roads:

"2.1.7 Size of Tire
Both the radius of the tyre and the aspect ratio H/W influence the rolling resistance. Rolling resistance can be reduced by increasing the radius and decreasing the aspect ratio of the tyre. Lower aspect ratio means increased stiffness of the sidewalls and thus lower hysteresis losses."

By taller I meant a larger radius. The trick is finding a larger radius tire with a lower aspect ratio (on a larger wheel) that doesn't widen the tire.
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