"Jeff Strickland" > wrote in message
...
> The tire sidewall can be calculated by multiplying the width (225)
> by the
> aspect ratio (.55 or .60).
>
<snippety snip>

All of what Jeff said is true, except you must also consider that some
(many) manufacturers vary their measurements and ratings a bit.

Anyway, you can get the real (measured) tire circumferences off of the
tirerack web site for any tire you are considering and then compare it
to the stock tires to determine how much actual difference ther will
be.

http://www.tirerack.com/index.jsp

By the way, it appears there is no shortage of the correct sized tires
there on their web site.

A larger diameter tire and the resulting taller gear ratio (smaller
number:1) may not be a bad thing if you are primarily a freeway
driver. OTOH you may want to go with a smaller diameter wheel for a
shorter overall drive ratio if you are more interested in acceleration
performance.

-Fred W