And the 15 is the size of the wheel it's designed for. So, in this case you've got a 31-inch tall tire for a 15-inch wheel. You know the wheel radius is 7.5-inches, and the tire radius is 15.5 inches.

A system for specifying tire sizes using the treadwidth (in millimeters), the aspect ratio, type or tire construction as well as the rim diameter (inches). The sizes are written as such: P215/50R17.

The R means the tire is of radial construction (they all are) and the 18 is the diameter of wheel the tire fits, expressed in inches. This string is a real hodgepodge of numbers but it carries the ...

The main focus of this guide is the aftermarket wheel size that started it all-width. That's right, way before there were 17s there were 17-inch-wide slicks slapped on the back of hot rods.

For example, 107.5 X .03937 = 4.23. Multiply the answer by two and add the wheel size like this (4.23 X 2) + 17 = 25.46. All this to figure out the tire stands roughly two-feet tall.

An 18-inch tire, for example, will probably weigh at least a couple of pounds more than a 16- or 17-inch tire. That could also be true of a larger-size wheel.

The sales trend tracks closely with original equipment fitment trends of the past few years. Those U.S. Tire Manufacturers Association (USTMA) data show nine of the 10 most popular OE tire sizes the ...

Large sport-utility vehicles and pickup trucks allow extra-large plus-size options up to 28 inches in diameter. We tested a late-model Chevrolet Tahoe SUV with plus-four and plus-eight wheels and ...