Help with revs per mile

[Riptide]

I have some NT05 tires from Nitto. 295/45/R18. Nitto's site says 730 revs per mile.

http://nittotire.com/#index.tire.nt05.sizes

I have a spreadsheet that calculates revs per mile and I also checked it with discount tire's online calculator. They both say 708 revs per mile for this tire size.
http://www.discounttiredirect.com/direct/brochure/info/tmpInfoTireMath.jsp

What's the problem? And which is the correct value?

 

[hate2work]

708.8 is correct, given the circumference of 89.39 inches.

63,360 inches per mile, divided by the circumference.

 

[Riptide]

I wonder why the Nitto site is so far off? They make the tire. :/

 

[XS650]

Originally Posted By: Riptide
I wonder why the Nitto site is so far off? They make the tire. :/


The basic elementary school level calculation that results in 708.8 revs/mile assumes that the tires is made exactly to the dimensions indicated by the tire size and that the tire is infinitely rigid, neither of which are true.

Could it be that Nitto knows more about their tires than some simple spreadsheet or a generic revs/mile calculator that ignores flex and manufacturing tolerances?

 

[Riptide]

Yah I think I'll just use the 730 figure until I get access to a GPS that will let me fine tune it.

 

[CapriRacer]

Allow me to confirm that the rolling diameter of a tire can not be measured directly. However, the rolling diameter is about 97% of the overall diameter. Most tire size calculators do not take this into account.

 

[rshunter]

Originally Posted By: XS650
Originally Posted By: Riptide
I wonder why the Nitto site is so far off? They make the tire. :/


The basic elementary school level calculation that results in 708.8 revs/mile assumes that the tires is made exactly to the dimensions indicated by the tire size and that the tire is infinitely rigid, neither of which are true.

Could it be that Nitto knows more about their tires than some simple spreadsheet or a generic revs/mile calculator that ignores flex and manufacturing tolerances?

That's all dirty corporate propaganda, and you know it!