Tire Sizes

[normstoy]

Can anyone tell me if there is a difference in changing winter snow tire sizes from the manufacturer size to another size. 17" - 16"??

Thanks,
Norm

[Pete_Coach]

As long as the circumference of the tire and wheel is very close to the original circumference, there will be no problem. There are may sites you can go to get the information and the one often used is http://www.miata.net/garage/tirecalc.html.
Generally, if you down one size in the wheel diameter, then you go up one size (10 mm) in tire size. For example 195 tire to 185 tire and higher aspect ratio. This is to preserve the drive train and speedometer accuracy.

[fastlayne]

A narrower tire for winter has the benefit of cutting through any snow and making contact with the road. (A relatively wider tire will ride up on the snow like a toboggan.)

For winter wheels it is common to drop an inch in the rim size, go from 195 to 185 (by subtracting 10) in width and go from a 55 series to 65 series tire (by adding 10).

For example,

Summer Tire = 195/55R17
Winter Tire = 185/65R16

Based on the Miata Tire Calculator the above tires have overall diameters that are within 0.1 inch of each other.

[normstoy]

Sincere thanks for your help.

[DavidY]

You cannot MINUS size (i.e., down on one nominal rim/wheel size) if your vehicle has big brake calipers....typically this is only an issue if you have a high performance car.

The overall tire diameter should be no more or less than 3% than stock.

Dave