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
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> Alistair Bell
> Sent: Friday, October 14, 2011 7:55 AM
> To: vanagon@GERRY.VANAGON.COM
> Subject: tire size calculator Re: tire circumference
>
> bookmark it Dave :)
>
> http://www.miata.net/garage/tirecalc.html
>
> alistair
>
>
>
> On 2011-10-14, at 7:16 AM, Dave Mcneely wrote:
>
> > I once knew a web site where one could enter a stock tire size and a
> replacement size, and get an odometer and a speedometer conversion factor.
> BTW, the difference is so slight for 185R14 vs 195R14 as to not be of
> practical significance.  But when folks go to the larger wheels and tires,
> it really matters.  mcneely
> >
> > ---- Robert Mac Dowell <yakandhike@COMCAST.NET> wrote:
> >> Let me rephrase that. How many RPM'S should it be for the speedo to be
> right
> >
> > --
> > David McNeely
>