>on 7/20/01 11:41 AM, Aristotle Sagan at killer_jupiter@HOTMAIL.COM wrote:
>
> > You have a couple of choices tire sizewize...
> > 205R65-15 or 215R60-15 are both about the equivalent of a 195R78-14. The
> > 185R7814 is a bit smaller.
> >
> > As your tire size (circumference) goes up, your speedo reads slower.
>
>
>by what percentage?  i mean, if i am showing 65, i'm going what, 67?
>
>bill
>'87 syncro westfalia
Specification   Diameter       Circum      Revs/Mile    Diff
185/80-14        25.7in         80.6in        786        0.0%
215/60-15        25.2in         79.0in        802       -1.9%
205/65-15        25.5in         80.1in        791       -0.6%
195/75-14        25.5in         80.2in        790       -0.5%
205/70-14        25.3in         79.5in        797       -1.4%

Or use this...
http://miata.net/garage/tirecalc.html

tim

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