funny, when i do it long hand I get 786 (for 80 profile). I must be making the same mistake as the miata calculator is doing.

let me work it out here:

185 mm = 7.283"

80% of that = 5.826"

add that twice to the rim diameter of 14" = 25.652" (overall tire diameter)

circumference is diameter X pi = 80.588"

inches in a mile = 63,360

63360/80.588 = 786.22

alistair

On 2011-10-14, at 4:36 PM, mark drillock wrote:

> That Miata calculator does not give me the numbers close to the factory
> numbers at all. What are you using for aspect ratio? I thought you got
> this already. The Miata.net toy does not have an option for 82 so 80 is
> the closest. When I put that in for 185/80R14 it gives 786 not 809. You
> only get 809 if you use the very wrong aspect ratio of 75.
> 
> Mark
> 
> Dave Mcneely wrote:
>> ---- Robert Stevens<mtbiker62@GMAIL.COM>  wrote:
>>>> 
>>>> I've been using http://www.1010tires.com/tiresizecalculator.asp to
>>>> see sizes, revs&  all that stuff for different sized tires.
>>> 
>> 
>> And, for whatever it is worth, this calculator gives 810 and a fraction revolutions per mile for the Hankook RA08 (or any other tire) in the 185R14 size, and 790 and a fraction for a 195R14 size.  That's very close, but not exactly the same, as the 809 that the Miata site gave for the 185 tire (the difference is less than 1%).
>> --
>> David McNeely
>>