It depends on the diameter of the tire wheel combination. You can find 14"
wheel/tire combinations that have a larger diameter than a given 15"
wheel/tire combination.  It is not likely to be found in practice, but it is
possible.

Take a look at the tire manufacturer's specifications for the diameter of the
14" and 15" tires, and you can figure out the difference.  Most manufacturers
also give a figure of revolutions per mile. If you look at the bottom of your
speedometer you will see a number - like 805 - which indicates the revs/mile
the speedo is calibrated to.

With a little math, you can figure out the difference. Of course, any good
speedo shop can recalibrate your speedo to the new tire diameter.

Todd
88 westy

Ed Shultz wrote:

> Hi List,
>
> When moving from 14" to 15" wheels on a Vanagon, how does that effect the
> accuracy of the spedo? A lot? A little? It seems the spedo is reading
> higher. But how can that be?
>
> Thanks,
>
> Ed
> Ed Shultz
> 1987 Syncro GL
> Photos: http://homepage.mac.com/eshultz/PhotoAlbum.html