Some days I feel like I’m surrounded by nothing but tires.  Okay, that might be because I work at a NJ car dealership.  I thought I’d spend a few minutes explaining what those letters and tires mean on your tire.

AOL Autos does a great job deciphering these codes:

Example Tire Sidewall Markings: P215/65R 15 95H M+S

- First up is a letter or letters, indicating the tire’s purpose: “P” for passenger cars or “LT” for light trucks are the most likely letters you’ll see.

- Next is a three-digit number. This is the tire’s width (in millimeters) from sidewall edge to sidewall edge.

- Then, a two-digit number which is the tire’s aspect ratio, or the ratio of height to width. The smaller the number, the shorter the sidewall.

- Next, a letter, probably “R,” which indicates radial construction. Almost every tire you encounter will be a radial nowadays, unless you’re buying tires for a classic car.

- Then, another two-digit number, which is the diameter of the wheel that the tire is intended to fit.

- Next, an optional two- or three-digit number. This is the tire’s load index number, and its inclusion is not required by law. The load index number corresponds with the tire’s load-carrying capacity. Discount Tire has posted a handy chart with the load index numbers and loads. Simply put, don’t install a tire with a lower load index number than your manufacturer recommends.

- Next, a letter. This is the tire’s speed rating. Follow your manufacturer’s recommendation. You should only need to upgrade to a higher speed rating if you have modified your vehicle for track use, or if you are heading to Germany to drive on the Autobahn.

- Next, some more letters, usually “M+S” or “M/S.” This stands for mud and snow, and applies to most radial tires sold in America.

There are more numbers and letters, most of which you don’t really need to worry about unless your tires are subject to a recall. They refer to the tire’s place and date of manufacture, the maximum inflation pressure, maximum load rating, composition, materials, tread wear, traction and temperature grades. Diving deeply into these ratings will yield a trove of information – most of which differs from manufacturer to manufacturer. Unless you are obsessive about your tires, you will probably be OK trusting in your tire guy’s interpretation of the small print.

The next time you shop for tires, you’ll understand what all those letters and numbers mean.  And remember, every good NJ tire center will help you select the best tires for your vehicle.