Tire sizing

[Doctordestiny]

What do all the numbers on a tire sidewall mean? I know what the 15, 16 or 17, for example, is, but what about all the other numbers: P185, etc.?

[photon]

the 185 refers to the tread width of the tire, and the other number is the profile, which is the ratio of the width to the height of the sidewall.

So a bigger first number means a wider tire, and a bigger or smaller profile means a bigger or smaller sidewall (the height of the tire from the rim to the edge of the tire).

There's usually a speed rating as well. H, V, Z, etc, which indicates how fast the tire is rated for.

[photon]

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

[Ironhorse]

Let's take a P225/45R17

The P refers to Passenger tire. Sometimes you'll see LT on a 3/4 ton truck for "Light Truck"

The first number (225) is the section width, in mm. The number after the slash (45) is the tire side wall height ratio, in percentage of the section width. The R stands for Radial construction, and the next number (17) is the wheel diameter.

http://www.tirerack.com/tires/tirete....jsp?techid=46