Tire diameter

[5pdrman]

I am putting a set of 15" aftermarket wheels on my '78 Spider and want to know the overall diameter of the origianl tire so that I can adjust my tire size to meet the correct wheel/tire diameter and not have a speedometer change. I don't think the tires I have on it now are stock.

Can I change the overall diameter a bit and how much to keep the speedo within 3-5% or is that such a small change in the tire size the it wouldn't make a noticible difference?

Larry

[courtenay]

Here's a tire size calculator: http://www.miata.net/garage/tirecalc.html I believe the original for the Spider was 165/85/13.

[narfire]

I am putting a set of 15" aftermarket wheels on my '78 Spider

I think most 15 inch wheels will use a 50 series tire. I have 15" with 50 series and when I measured the original 13 inch diameter I was maybe 1/4 inch different? Thought it was around 23 inches???

[4uall]

fyi http://www.carfolio.com/specifications/ ... car=100397

[wiggo]

I think most 15 inch wheels will use a 50 series tire.

Agree. My VX was factory fitted with 195/50x15 on 7x15 wheels.