quattro digest, Vol 1 #4414 - 7 msgs

[George Selby]

At 12:00 PM 1/1/03, you wrote:
>If I could use the 206/60/15 size with zero change in tire diameter, and I
>haven't looked at this up to this point, then I would use the Touring LH
>tire again.

Tire sizes have an industry standard 7% variance allowable from "true"
dimensions stamped on the side.  So a 195/65/15 has a theoretical diameter
of 24.98", a 205/60/15 has a diameter of 24.68" and a 215/60/15 has a
diameter of 25.15".  Doing some computation, the 205/60 is 1.2% smaller in
diameter than the 195/65, and the 215/65 is 0.5% larger.  Both of these
tires are very close in size to the stock size, and when you include
industry allowable variances, you discover that either tire will not result
in any noticeable speedo differences.  In fact, you may discover some
brands 215/60/15 are smaller in diameter than some other brands 195/65/15.

What I'm trying to say, is that, in my opinion, that the "wanting it the
exact diameter" is not a valid excuse for not getting larger tires in the
plus 0 size, since the exact diameter is a 7% window, not an exact number,
and several plus 0 sizes came within 1.2% or less of the stock size.  Did
you know that most German speedos read very high (they read faster than you
are going, as much as 5-8 mph on BMW's for instance) to accommodate larger
tires being fitted on the vehicle (German law mandates the car CANNOT be
travelling faster than the speedo reads) so I would be inclined to stick on
the 215/60/15's

George Selby
gselby4x4 at earthlink.net