Microl Toyota

"It's just a tire."

It is amazing how most people pay so little attention to the tires that get them to and from work, carry their family members from place to place and haul everything from groceries to Little League teams. The tires can be new or used, cheap or expensive, but no matter what, we expect them to function without fail - forever… and then get mad when they wear out or go flat. Tires do wear out. This is a fact of life.

We can help prolong the tire's lifetime, but we cannot stop them from being damaged or wearing out. The following information is basic and consumer oriented in nature and may help us get a few more miles out of our tires.

There are literally thousands of different tire sizes and styles. They come in varying heights, widths, tread patterns, ply thickness, speed - temperature and tread wear ratings. To complicate matters, the rims on which they are mounted also come in a wide variety of sizes, styles, widths, materials and lug patterns. To calculate the total number of tire to rim configurations would be nearly impossible. So where do we start when we need new tires?

The best place to start is the tag on the driver's door column of all U.S. Specification vehicles. Federal Law requires that the tag contain information regarding the correct tire size, rim size and proper tire pressure. Let's look at the tire information there and try to make sense of it. This tag contains information on both the front (FRT.) and rear (RR.) tires. The front axle will support 3160 pounds with P245/70R16 tires, mounted on a 16 inch by 7-inch rim, inflated to 26 pounds per square inch when cold. So what is a "P245/70R16"? That is the specified tire size for the vehicle. The first letter, "P", stands for Passenger. It means that the tire is designed for use on passenger vehicles like sedans, sport utility vehicles or light trucks.

The "245" means that the tread pattern is 245 millimeters wide. The "70" refers to the sidewall height (also known as the "profile"). It means that the height of the tire from the bead (where the tire seats on the rim) to the tread is 70 percent of the tread width. In this case, the height is 171.5 millimeters (245 times 70%). The letter "R" stands for "Radial". That refers to the construction of the tire, using radial steel belts. The "16" is the specified diameter of the rim. It is 16 inches. Rims also have a specified width; in this case that would be 7 inches. Tires and rims must match to be safe.

The reason that the rim must fit the tire is safety! The tire and rim combination carries a lot of weight and must distribute that weight over a limited area. If a rim is too narrow or too wide, the tire may not be able to withstand the weight. The tire may rupture (blow out) and cause severe damage to the vehicle and it's occupants.

Okay… our tire is now the right size for our vehicle and it fits properly on the rim. What's next? Before we mount the wheels, we have to make sure they are balanced. Tires and rims are not perfect. They will be spinning at great speeds (how fast do we normally drive?). In order to minimize vibrations at high speeds, our wheels have to be balanced. The majority of tire shops now use high speed, computerized spin balancing machines that pinpoint exactly where wheel weights should be placed and how heavy those weights should be. This balancing act offsets the minor imperfections in the tire or rim.

Unbalanced tires will have a tendency to wobble or bounce, which can damage the tires and the vehicle over a period of time. Proper balancing prevents most of the problems associated with tire "run out".

Now that we have the proper tire that is matched to our rim and it is balanced, how do we securely mount them to our vehicle? If we had changed the rims, we would have to be a little more careful.

Lugnuts must also be matched to the vehicle and the rim, in order to hold them securely in place. Lugnuts (like the tires and rims) come in a wide variety of shapes and sizes. The lugnuts we chose should match the vehicle they will be installed on as well as the wheel they are going to secure. Following is just one example of how the wrong lugnuts can cause a great deal of confusion and money…

Click here to find out more about lugnuts and how to safely mount the wheel.

Click here to learn about tread wear related tire pressure and proper tire repairs.

Click here to learn about more unusual tread wear patterns and spot tires that are out of alignment.