Maybe if we try the percentage difference in diameter?

The following is done on a friday, errors are inherent.

Diameter = wheel size + (2 x ratio x width)

Therefore diamter of a 205-70 on 15" is 26.3in

and a 185-70 on 14" is 24.2in

Difference is 8.6 %

Speedo will read about 8-9% slower?

�ric

At 02:52 PM 20/07/2001, Bill Kasper wrote:
>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
>http://www.scruznet.com/~kasper/pics/westy/