What tire size to buy?

I have a set of Rallye wheels 14" x 6" and 14" x 7" that I will be using on a Vega project. I cannot use a tire with an outside diameter bigger than 24", what tire size should I purchase? Will a 185 x 65 x 14" work? A 185 x 60 x 14" is about 22" diameter, this is too small. How about a 70 series tire? Any advice will be welcomed here, I want to keep everything under the very small fenders. Thank you, Bill

Hi Bill,

It would be a good idea to check the tire manufacturer's specifications since actual dimensions often vary from brand to brand. Also check their rim width recommendations ... I think a 185 would be a bit on the narrow side for the 7" wheels.

Given your 24" diameter requirement and 14" wheels, you basically need a tire with a 5" sidewall. Calculating for various aspect ratios (and rounding off a little) gives the following:

70 series = 180/70R14
65 series = 195/65R14
60 series = 210/60R14
55 series = 230/55R14
50 series = 245/50R14

Of course, not all of those end up being actual available tire sizes. If the 24" diameter isn't an absolute max limit, I think 215/60R14's would be a good choice. They're only a tiny bit over 24" diameter (about 24.2") and would be a good fit (width wise) on both the 6 & 7" wide wheels. The 245/50R14's (about 23.7" diameter) would work on the 7" wheels but they're a bit wide for the 6" wheels.

I know you have 14 inch rims, but if you can swing for the 15s, there is a huge selection in the 225/50 and 205/55 tires for the Miata Spec racers.