Quote:
Originally Posted by RPM
Thank you Barry, I love your site and was reading it before I posted my question.
The data you used in your regression doesn't include any low profile tires so I was wondering whether you could apply the formula in this case.
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The formula was derived from the data available. The data did not include lower aspect ratio sizes, but "if everything else were equal", there is no reason to believe the trends shown in the data would change the formula. It would be nice to find some confirming data, or data which expands the range.
There is however an odd thing I should point out - and it's the "Everything else being equal". Lower aspect ratios tend to use higher speed ratings. For example, Tire Rack lists in a 195/60R15 size, 1 S, 6 T, 25 H, and 2 V speed ratings. In a 195/50R15: 1 T, 1 H, and 7 V speed ratings.
I can argue that, more or less, all S and T rated tires are built the same. But I can NOT argue that H rated tires are the same as the S's and T's - and the V's are another thing again.
That difference in construction affects RR - higher speed ratings having more material would have higher RR values - PLUS - higher speed rated tires also tend to have higher grip levels, by sacrificing treadwear and RR.
So that "Everything else being equal" creates a situation that doesn't reflect reality.