Tire Glossary

Air Pressure:

The amount of air inside the tire. Air pressure is typically measured in pounds per inch (PSI). You should always wait a minimum of three hours after the tires are driven to measure the air pressure. If you measure the air pressure shortly after your vehicle has been driven, it could result in an inaccurate reading.

Alignment:

Tire alignment involves ensuring the vehicle’s wheels, steering, and suspension are adjusted to the manufacturer’s specifications. Wheels that are in alignment are in the optimal position for driving. Misalignment of the wheels can be caused by an accident, even a minor one such as hitting a curb or a pothole.

All-Season Tires:

A type of tire designed to provide adequate traction and grip in a wide range of weather conditions. Despite being called all-season tires, the capabilities of these tires are often compromised in harsh winter weather, which is why some manufacturers are starting to refer to them as three-season tires (spring, summer, and fall).

All-Weather Tires:

Similar to all-season tires, all-weather tires are engineered to perform year-round. However, unlike all-season tires, they include features designed for driving in the snow and freezing temperatures. As such, all-weather tires are usually Three Peak Mountain Snowflake certified, whereas all-season tires are not.

Aspect Ratio:

The height-to-width proportion of the tire. For example, if the sidewall’s height is 55% of its width, the aspect ratio is 55.

Asymmetric:

Asymmetric or asymmetrical tires are tires with a tread design where one side of the tread pattern is different from the other side.

Balancing:

Balancing the tires means adjusting them in a way that when they spin, they evenly distribute weight. Unbalanced wheels can lead to tire vibration.

Bead:

A rounded, C-shaped piece of steel wire with steel reinforcements, located inside the tire, where the tire connects to the wheel.

Belt:

Bias Ply Tire:

A tire designed with criss-crossing plies for extra strength.

Carcass:

The supporting structure of the tire, beneath the tread and sidewalls. The carcass consists of plies anchored to the beads on each side.

Contact Patch:

The portion of the tire that comes into contact with the road while rotating. The contact patch is sometimes referred to as the footprint.

Cord:

The strands of material that make up the tire layers. These strands are typically made of steel, polyester, fiberglass, nylon, or rayon.

Directional Tread:

If a tire has directional tread, it means that it was engineered to roll in one direction only. As such, directional tires are most often used on one side of the vehicle.

Flat Spot:

Uneven or irregular wear in a particular, isolated area of a tire’s tread.

Footprint:

The portion of the tire that comes into contact with the road while rotating. This is sometimes referred to as the contact patch.

Groove:

Also referred to as tread grooves, a groove is a space between two tread ribs. Often the depth of the grooves is mentioned, as the deeper the grooves the more traction they offer, especially in wet conditions.

Heat Cycling:

Heat cycling refers to a method of breaking in new tires before using them in a racing competition. Using this method, tires are slowly heated in a controlled environment, giving them more traction and longer tread life.

Highway Tires:

Also called summer tires, highway tires are specifically engineered for wet and dry road conditions in mild to warm temperatures. They are not suitable for driving in winter conditions.

Hydroplaning:

Hydroplaning is a condition where the tires lose contact with the road when driving on wet surfaces like rain or ice. The result is that the vehicle stops responding to the steering wheel, and instead, the tires slide or skid on the layer of water or ice rather than on the pavement.

Inner Liner:

The inside layer of a tubeless tire, which works to prevent air from penetrating the tire wall.

Load Carrying Capacity:

The maximum amount of weight a tire can carry.

Load Index:

Low-Profile Tire:

Low-profile tires are generally viewed as high-performance tires. They have a shorter sidewall and thus a lower aspect ratio, which offers better handling but at the expense of ride comfort.

Maximum Inflation Pressure:

The maximum air pressure to which a tire should be inflated. This number is typically listed on the sidewall of the tire or a sticker on the driver’s side door of the vehicle.

M+S/M&S:

Mud and snow, a designation found on the sidewall of the tire. The M+S designation is typically found on all-season tires and confirms that the tire has been successfully tested in these conditions.

Mounting:

The act of installing a tire on a wheel. Although tires can be mounted at home, it is generally recommended that new tires are mounted and balanced by a professional mechanic.

Negative Camber:

A unique alignment style where the tops of the tires are angled inwards, towards the center of the vehicle. This type of alignment provides better grip, especially when going around corners, which makes it popular for race cars.

Negative Offset:

A situation where the wheel mounting surface is towards the back of the wheel. When a wheel has a negative offset, the tire and wheel are removed from the wheel well.

Offset:

The distance between the wheel mounting surface and the centreline of the wheel.

Original Equipment (OE):

This is a term used for the tires that come with a new vehicle that’s been purchased. These tires are chosen by the vehicle manufacturer, typically to best complement the vehicle’s unique capabilities and characteristics.

Overall Diameter:

The diameter of an inflated tire, minus the load.

Overall Width:

The distance between the tire’s outer sidewalls.

PennyQuarter/Toonie Test:

A simple and easy test used to check the tread depth of your tires. In the United States, the test is performed with a U.S. penny. In Canada, the test can be performed with a quarter or toonie. There is a direct correlation between tread depth and traction. As such, the test reveals whether your tires are worn beyond a safe level and should be replaced. To use the quarter test, place a quarter with the caribou facing down into one of your winter tire grooves. If you can still see the tip of the caribou’s nose, it means the tread depth is no longer adequate. To use the toonie test, insert a toonie into the groove. If you can see the bear’s paws, your tires still have plenty of life left in them. However, if the silver part of the toonie is covered by the tread block, it means your tires are about 50 percent worn, and if the tread only reaches as far as the words “Canada” or “Dollars,” then your tires are extremely worn and should be replaced as soon as possible.

Placard:

A label found inside your vehicle (typically on the driver’s side door or in the glove compartment) that features important information about your vehicle, such as the recommended tire inflation pressure, gross vehicle weight, etc...

Plus-Sizing:

Customizing your vehicle by adding wheels that are larger in diameter and low-profile tires for aesthetic and performance reasons. Plus-sizing tires allow the overall diameter to remain the same.

Ply:

A rubber-coated layer of cords that make up the internal structure of the tire. Plies run from bead to bead and can be found between the inner liner and the tire tread.

Ply Rating:

The load-carrying capacity of the tire in relation to the number of plies.

Positive Camber:

Opposite of negative camber, an alignment style where the tops of the tires are angled outwards from the center of the tire.

Positive Offset:

A situation where the wheel mounting surface is towards the front of the wheel. When a wheel has a positive offset, the tire and wheel are moved inwards, towards the vehicle.

PSI:

PSI stands for “pounds per square inch” and is the standard unit of measurement for tire pressure. The recommended air pressure for most tires is between 30 and 35 PSI, and all tires have a maximum PSI rating.

Ride Matching:

A way to balance wheel-and-tire assemblies using simulated roads tests, in order to provide optimal weight distribution and prevent tire vibration.

Rim Width:

The distance between the two inside edges of a wheel or rim.

Rolling Resistance:

The amount of force needed to keep the tires moving at a constant, uniform speed. Rolling resistance directly correlates to energy. The lower the rolling resistance, the less energy the tire uses, which is why a low rolling resistance is almost always a feature of eco-friendly tire products.

Rotation:

The act of moving tires from front to rear, side to side, or in another pattern. The reason behind rotating your tires is to promote even wear and longer tread life.

Run Flat:

Tires designed with self-supporting sidewalls that allow the driver to continue driving for a set distance after suffering a puncture.

Shoulder:

The part of the tire where the sidewall meets the tread.

Sidewall:

The side of the tire, located between the bead and the tread.

Sipes:

Part of the tire’s tread design, sipes are small slits within the tread that increase traction and grip, especially in wet, snowy, or icy conditions.

Snow Tire:

Snow tires, also referred to as winter tires, are tires specifically designed to be driven in harsh winter conditions, such as snow, slush, and ice.

Speed Rating:

The highest speed that a particular vehicle can travel at safely. Generally, the higher the speed rating, the better the handling.

Studs:

Metal or plastic pins that can be inserted into the tread of a tire for added traction. Studs can only be used on studdable tires, and are most often seen on winter or snow tires to increase traction in winter conditions.

Symmetric:

Symmetric or symmetrical tires are tires with a tread design where both sides of the tread pattern mirror each other.

Three Peak Mountain Snowflake:

A certification indicating that the tire meets the required performance criteria to be considered reliable, even in severe snow. If a tire is certified, the Three Peak Mountain Snowflake symbol can usually be found on the sidewall of the tire. Winter tires, along with some all-season and all-weather tires, are the most likely to have this designation.

Tread:

The tire tread is the part of the tire that makes contact with the road or other driving surface.

Tread Depth:

The distance between the top of the tire and the bottom of the groove.

Tread Life:

The expected lifespan of a tire before it wears out. Typically measured in miles (U.S.) or kilometres (Canada).

Valve:

The valve allows air to flow in and out of the tire and work to prevent air from escaping the tire.