Speedo Error vs. Tire Size
 

My boss at work is a car guy. He fully restored an XKE and it is now number 2 or 3 in the country in concours points. It looks better than "showroom new."
He knows that I am comtemplating putting oversize rims & tires on SVXY (92 pearl SVX). So, this morning at work, he gave me an Excel program that computes % speedo error vs. tire size. I loaded it into my locker for everyone to use. We were pretty busy at work this morning, so I didn't even get a chance to look at it.
So don't ask me anything about it until the middle of next week.

Have fun everyone.

Very nice indeed :) :)
and you don't need to be online to use it like these;

Miata Calc

Dakota Calc