Posted by Crash-Test Dummy on October 07, 1999 at 15:27:53:
Why is it that when I try to calculate the revolutions per mile for a tire (using its width, aspect ratio and wheel diameter) I always seem to come up different number than the manufacturers list in their brochures and websites? The one reason I can think of for my not being able to calculate it is tire "growth" due to centripetal force while rolling.
When I went to Tire Rack's website's winter tire area and told it what kind of car I have, it came back with different "minus 1" tire sizes than my calculations indicated. My car has OEM 215/50-16 tires, and Tire Rack's website recommended I go with 205/60-15 rather than the 185/65-15 I calculated as being closest in circumference to my OEM's.
I have also noticed that, for a given tire size, two tire manufacturers are likely to list different revolutions per mile. Do the manufacturers caclulate the revolutions per mile, or is it measured?
Appreciate all help.