Shopping for Tires? 10 Tire Terms You Should Know


tire that needs to be inspected for small holeBuying new tires shouldn’t feel like a day in a foreign land—especially when buying the right set of tires is so important. Tires are the vehicle’s sole point of contact with the road; when roads are wet or icy, that point of contact becomes a vital safety measure. For that reason, it makes cents (pun intended) to learn the terms that come with tire shopping so you can purchase the right tires for your car or truck (and for your wallet).

All-Season Tires

All-season tires are manufactured to perform in a variety of conditions year-round. With all-season tires, there is a give-and-take. While these tires offer a quiet ride and are a good all-around tire for general driving conditions, all-season tires are not specifically designed for winter driving. If driving on icy roads is a must during Wisconsin winters, snow tires are usually recommended.


Tire balancing is an essential part of buying new tires and ongoing tire maintenance. Tires, even new tires, can be imbalanced on a set of rims, resulting in vibrations and uneven or premature tire tread wear. During tire balancing, the mechanic scans the tire and wheel rim and adds weights so the tire spins evenly. When purchasing tires, make sure that the mounting process includes a tire balance. Schedule a follow-up tire balance every 6,000 miles to maintain an evenly balanced tire (and an evenly wearing tire so tires do not need to be replaced more often than needed).


New tires are mounted on to a set of rims after a purchase. Old tires are removed, or unmounted, from the previous wheel rims.


Overinflation is when a tire is filled with too much tire pressure. Tires with too much tire pressure can decrease gas mileage and cause the uneven wear of tire treads. Think of an overinflated tire as a ball with too much air; only part of the ball touches the ground, just as only part of the tire comes into contact with the road. This can cause parts of the tire tread to wear more than other parts and cause the car owner to pay for tires earlier and more often. Maintaining proper tire pressure is an essential part of car ownership. The correct tire pressure can be found on a decal on the inside of the driver door and in the user manual (use these directions to check tire pressure on a regular basis).

Penny Test

The penny test is the way to check a tire tread to ensure there is enough for safe driving; bald tires (tires with low tread) can be dangerous to drive on, especially when roads are wet or icy. Bald tires are also more prone to blowouts.

To do the penny test, place a penny into the tread of the tire. Check to see how much of Abraham Lincoln’s head you can see above the tread. If Lincoln’s head can be completely seen, the tire tread is low. The penny test should be performed at multiple places around the tire; tires can wear unevenly. If the penny test shows an extremely uneven tire tread wear, schedule an appointment with a mechanic to determine the cause of uneven wear. Uneven tire wear can be a sign of a problem, such as a worn suspension part, alignment issue, or improper tire pressure.

Pounds Per Square Inch (PSI)

Pounds per square inch, or PSI, is the amount of pressure that should be in a tire. The correct PSI of a tire can be found on a decal on the inside of the driver door and in a user manual. Tire pressure should be checked every month or when there is a drop in the air temperature. For directions on how to check tire pressure, click here.


Rims, or wheel rims, are the circular metal parts that tires are mounted on. When tire balancing, weights are applied directly to wheel rims. Wheel rims do need to be replaced when there is an excessive amount of corrosion or other conditions that can cause the rims to leak air.

Snow Tires

Snow tires are specifically designed for traction and handling on icy and wet winter roads. Constructed with a softer compound and tread pattern designed specifically for getting through snow and ice, snow tires can find traction. It is important to note that traction control is not a replacement for snow tires; traction control adjusts the speed of tires to conditions, but does not give a vehicle more traction while driving.

Because snow tires are designed specifically for winter conditions, drivers should make an appointment to have snow tires mounted when the temperature dips below 40 degrees on a regular basis. The snow tires should be removed when the temperatures are consistently in the upper 40s or low 50s.

Tire Aspect Ratio

The tire aspect ratio are the measurements that, collectively, indicate the size of the tire. The tire aspect ratio is found on the tire currently on the car, in the user manual, and, often, on the inside of the driver-side door. (Some vehicles can be fitted with different size tires-check your user manual.) Tire aspect ratios contain a letter and a series of numbers, such as P235/55R17.

The P in the tire aspect ratio indicates that the tire is intended for passenger cars. Other tire aspect ratio letters could be LT, ST, C, or T. The first numbers of the tire aspect ratio are the width, in millimeters, between the two sidewalls. The series of numbers, in this example 55, is the aspect ratio. The number is a percentage, and the higher the percentage, the larger the sidewall of the tire. The last number, 17 in this case, is the diameter of wheel that the tire fits on.

Tire Tread

The tire tread is the surface of a tire; tire treads are specifically designed for certain purposes, such as for snowy road conditions or for heavy commercial use. Tire treads are also important to monitor; low tire tread can cause improper water channeling, unsafe driving, and premature blow outs.

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