I am a retired dragracer building my first pro touring car. I am having a hard time converting the tires I am use to - measuring 29" tall X 18" wide on a 15" rim. Can someone point me in the right direction converting these measurements to metric measurements. I need a tire that is 29" tall X 12.5" wide to fit a 15X10 inch rim - how do I convert??

I'm sure you can find conversion calculators on google or you can to to www.tirerack.com (http://www.tirerack.com) and look up tires by size and it gives you the measurements.

Multiply the width X 25.4 to get your mm sizing so 12.5 X 25.4=318
total height of tire = rims + sidewall heightx2.

To find aspect ratio:
divide the side section of tire by the width.

if the rim is 15" then the combined upper and lower side sections must be 14 to make up the 29" height.
14/2 =7 7 being the section width.
7/12.5 is roughly 56 round to 55 as I've never seen a tire that wasn't a product of 5 and you end up with a 55.
So I believe your looking for a 318/55 r15 tire.

Just checked the closest is a 315/60R15 or a 325/60r15

I am a retired dragracer building my first pro touring car. I am having a hard time converting the tires I am use to - measuring 29" tall X 18" wide on a 15" rim. Can someone point me in the right direction converting these measurements to metric measurements. I need a tire that is 29" tall X 12.5" wide to fit a 15X10 inch rim - how do I convert??

A 315/60-R15 will be 12.4" wide and 29.88" tall.
A 315/55-R15 will be 12.4" wide and 28.64" tall.

Good luck finding them. I assume you're looking for a drag radial because that's the only thing I've ever seen in that size.

Tire Rack has a couple of them for $199 each.

Tony,

Please spend some time in Cokers site b/c they list all the re-pop's sizes they sell.

Great info by me and I hope their real slicks are just that, real like I bought back then.

pdq67

http://www.miata.net/garage/tirecalc.html:thumbsup: