How does tire inflation pressure effect revolutions per mile of a tire?

Question

please include specifics if you have them. I know that rolling radius is reduced, but this doesn't effect revs/mile because the steel belts in the tire do not expand or shrink with air pressure variations (much). Do you know of a formula for calculating an approximate change in rev/mile based on tire pressure? SAE derived formulas would be awesome but without paying SAE, I haven't found anything specific in a very exhaustive web search. All I can find is the usual "air pressure affects fuel economy and can effect speedometer readings"

Thanks

http://mgaguru.com/mgtech/tires/ti103.htm

This link actually explains the reasoning for lack of delta for revs/miles, but it's the only example I've been able to find with actual numbers.

Thanks for the website Jessica ... I'll try to find an equivalent site to get your answers :-)

Answer 1

yes it does. simply because you will be having a slightly smaller radius if it is low or, a slightly higher radius if it is high. it is true it does effect fuel economy because if you have ever rode a bike with a flat tire you know it is very difficult to do so. with cars the harder the engine works the more fuel is required to maintain your performance demands.

Answer 2

You are right that the steel belts are not going to stretch or shrink, but they do change shape. When the tire is underinflated, it is flatter at the bottom and the car is lower to the ground.. Take a ruler and measure the distance from the center of your wheel to the ground. Then change the tire pressure and measure again. The ratio of these two reading will the ratio of the change in revolutions per mile.

Answer 3

circumference = pi*d 22/7*22.5 = 70.sixty 5 inches sixty six.a million miles in accordance to hour = 66360 inches an hour 66360/60 =1106 inches in a minute so the style of revolutions in accordance to minute = 1106/70.sixty 5 = 15.sixty 5 close to to fifteen and a 0.5 revolutions