by William Collins

Created on: December 31, 2009

Whether you drive a quaint little sedan, a large family-sized SUV, or a 1-ton pickup truck towing a trailer, you need to be aware of the tires that keep you safe on the road. This article will explain what you should know to make wise choices in tire selection and maintenance.

—Types of Tires—

Tires are made of many layers of rubber, steel and fabric. They are tailored to fit the type and size of vehicle they are intended for. As such, you need to understand what kind of tire to buy. There are three broad categories of tires: passenger, truck and trailer tires.

­­­­—What the Numbers Mean—

Every tire has letters and numbers that tell you what they are for and how they were made. Let’s explore these codes and find out what they mean.

As an example let’s use a tire size number such as P225/80R15 92S.

The first letter of the tire size will tell you what type of use the tire is meant for:

P signifies that it’s a metric “passenger” car tire.

If it starts with just a number (225/80R15 92S) then it’s a European metric tire.

T signifies that the tire is meant as a temporary tire, such as those “space saver” spares.

LT means that it is a Light Truck tire

ST means that it’s a “Special Trailer” tire. These tires should never be used on cars or trucks, only on boat, car or utility trailers.

The second set of numbers (225 in our example) means that the tire is 225 millimeters in cross section from the widest point on the inside sidewall to the widest point on the outside sidewall. It’s the “section width”, or how fat the tire is.

The third designation (80 in our example) refers to the “section height” (aspect ratio) of the tire, or how tall it is. The number 80 in this case means that the height of the sidewall, from the tread to the rim, is 80% of the “section width”.

The fourth designation (R in this case) refers to the type of internal construction.

R means the tire is a Radial tire, or the body plies radiate from the center of the wheel; most tires are of this type.

D would mean that the internal body plies crisscross in a Diagonal fashion. Also known as a “bias ply” tire, they are used for spare tires and for light trucks.

B designation means it’s a “belted” type of tire. The tire is a “bias ply” tire that is also reinforced with belts under the tread area. It’s very hard to

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