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Tire Radius:
7.50X20 = 17.0 8X22.5 = 17.1
8.25X20 = 17.6 9X22.5 = 17.9
9.00X20 = 18.6 10X22.5 = 18.6
10.00X20 = 19.2 11X22.5 = 19.2
11.00X20 = 19.7 12X22.5 = 19.7
12.00X20 = 20.4
Tire Revolutins per mile:
7.50X20 = 568 8X22.5 = 563
8.25X20 = 549 9X22.5 = 543
9.00X20 = 520 10X22.5 = 529
10.00X20 = 504 11X22.5 = 501
11.00X20 = 487 12X22.5 = 487
12.00X20 = 470
Of course, these are generalizations/averages. Different manufacturers will make things differently so to make sure of your calculations you will need to measure your own tires.
As you can see on the chart, going from a 11.00X20 to a 12X22.5 is not a calculable difference.
I would agree the gentleman didn't experience a change by going to tubeless tires. If the gentleman had gone to a 12X24.5 he would have seen the same difference had he gone from a 9.00X20 to a 11X22.5 or a 10.00X20.
Changing the number of rotations a tire makes in a mile by 15 or 20 RPM's can make a significant difference.
Good luck and happy trails.
Mark O.
So, moving a bit off topic, does moving from a tube type tire to a tubeless improve the ride?
John the Busboy
I have always found the tubeless ride better. They also seem to go more miles than the tube type. And around here at least, the tubeless are considerably cheaper than the tube type plus the cost of the tube.
As for the formula for figuring out RPM's, I think it is circumfrence divided into 5280.
I cheated by using the chart the state of WA uses in the "SPECIFICATIONS FOR SCHOOL BUSES".
It is so much easier using someone else's work. <G>
Mark O. |
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