It's time for new tires. My OEM size is 255/65/17. But there is a bigger selection in the size 265/70/17... My question is, is the size pretty similiar. Is it going to be bigger/smaller? Is it going to handle any differently?? Thanks.

 

The number after the slash, in this case “70,” is a percentage; the distance from the rim to the tread, in a properly mounted and inflated tire not supporting a car, is 70% of the width of the tire. So 70% of 265 = 185.5; from the rim to the road is 185.5 mm (about 7.3 inches). Basically, the number tells you how tall the tire is; it is sometimes called the aspect ratio or the profile of the tire. The new tire will be slightly wider and slightly taller.

 

Try this http://www.miata.net/garage/tirecalc.html