Agreed, and I have done so but for a multiple rotations to get better
accuracy. Unfortunately sometimes we want to know how a tire we don't
own yet compares to stock size. Or we are thinking about changing to a
larger rim size and want to know what sizes of tire for it will get the
gearing change we want or help us avoid a gearing change we don't want.
Then we need accurate rev/mile data from some external source.

Mark

Don Hanson wrote:
> Better yet...measure your tire.   Mark where the tread is, on pavement as
> the tire is normally inflated and while on the van.  Mark the tread of the
> tire, then roll the van till the tread mark hits pavement again.  Mark
> that.  Measure.
>    Divide by appropriate system of measurement used in your home country...US
> would be distance in feet into 5,280 feet= rotations per mile.
>
> On Fri, Oct 14, 2011 at 9:14 AM, Jeff Schwaia<vw.doka@gmail.com>  wrote:
>
>> Those calculators are good for an approximation, but each brand (or model)
>> will have a unique specification.  You should be able to find the actual
>> specification if your tire is still in production.  Tire Rack (
>> tirerack.com)
>> is really good at providing this type of information.
>>
>> Cheers,
>>
>> Jeff
>