Hey Eagle . . .

Centrifugal force only kicks in at extreme RPMs - like what you see in a 'wrinkle wall' tire on a dragster during burnout . . . but CF doesn't help the tire to carry weight or to put horse power on the ground . . . which is why the effect at burnout is very different from what you see as the same tire 'piles up' behind the contact patch when a dragster comes out of the hole on a real launch.

For regular street driving the technique that El Ply has pointed out is an excellent approach to accurately measuring effective diameter. It also points out the real problem of under-inflation. When a tire is under inflated the sidewall gets crushed down several inches at the bottom of every rotation - and expands as it leaves the loaded portion of the wheel - if RPMs are high enough it will stretch under centrifugal force (as you have surmized) as it goes over the top - this 'kneading' creates heat in the rubber and an when exteme can cause a sidewall to soften to the point of blow out.

Thanks for the table data Carolines Truck!

regards,
stock49

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