Tire Resources

History

Tire, or tyre, as the British spell it, is made up of rubber and fabric as well as other compound chemicals. The design and construction of these materials incorporate a tread and the body.

The purpose of the tread is to provide traction while the body provides structure and strength.

The most common and popular type of tire is pneumatic, which consists of a rubber-processed ring with a tread covering the circumference. The resulting chamber is filled with compressed air, or sometimes, nitrogen. The tire carcass also contains reinforcing materials such as fabric and wire, or steel.

The first practical pneumatic tire was made in 1887 by Scotsman John Boyd Dunlop for his son's bicycle.

But it was Charles Goodyear who, in 1843, invented a chemical process called vulcanization which converted rubber into a more durable material by heating it and adding sulfur and other chemicals. From this process, the first rubber-based tires were created.

The vulcanization process expanded the use and applications of rubber, and greatly enhanced the progress of the Industrial World.

As a result tire manufacturers grew with the start of the automotive business. Currently, more than one billion tires are produced every year.

Definitions

The tread is the part of the tire which contacts the road surface.

The contact patch, or footprint, of the tire, is the area of tread which is in contact with the road surface.

Each tire has a treadwear grade which identifies how long the tire's manufacturer expects the tire to last.

Part of a tire's design may include sipes, which are small cuts that provide greater traction in wet or icy conditions.

Tread wear bars (or wear indicators) are a safety feature located at the bottom of the tread grooves which indicate the tire has reached its wear limit.

The bead is a part of the tire which interfaces with the wheel rim.

The sidewall is the part of the tire that is the bond between tread and bead. The sidewall incorporates rubber and fabric plies, which are layers of material that provide strength, structure, and flexibility.

The shoulder is the part of the tire at the edge of the tread as it connects to the sidewall.

Tires are mounted to wheels that bolt to the vehicle's hub. There are many different types of wheels manufactured by the car companies and by the aftermarket.

The valve stem is a tube made of steel or rubber attached to a metal valve used to inflate the tire with air after installation or make subsequent tire pressure adjustments. Valve stems usually protrude through a pre-cut opening in the wheel to enable inflation by compressed air.

Radial tire construction utilizes body ply cords extending from the beads and across the tread so that the cords are laid at approximately right angles to the centerline of the tread, and parallel to each other. Additionally, sturdy stabilizer belts are placed directly beneath the tread. The advantages of this construction include longer tread life, better steering control, and lower rolling resistance.

Rolling resistance is a result of the deformation of the tire when in contact with the road surface. As the tire rolls, tread meets with the contact area and is deformed flat to conform to the roadway.

Each tire manufacturer lists a recommended inflation pressure for the vehicle's stock tires, which permits safe operation within the specified load rating and vehicle loading. If tire pressure is too high, the tire contact patch is reduced. In addition, ride comfort is reduced and the center of the tread may wear more quickly than the shoulder. Conversely, if the pressure is too low, the load capacity of the tire is diminished and premature wear, damage, or failure can occur.

Tires are specified by the manufacturer with a maximum load rating. Loads exceeding the rating may lead to unsafe conditions that can cause steering instability and possible rupture of the tire.

The speed rating denotes the maximum speed at which a tire is designed to be operated, according to the tire manufacturer.

Care and Maintenance

Rotation: Tires may exhibit irregular wear patterns once installed on a vehicle.This may be due to over- or underinflation, poor alignment, flat spots, damage to the tire (such as hitting a pothole) or other factors. Front wheel drive vehicles will traditionally wear out their front tires at a faster rate compared to the rears. Tire rotation is a common and important procedure that moves tires to different car positions, such as front-to-rear, in order to even out the wear, thereby extending the life of the tire.

Balance: When a wheel and tire are rotated, it will wield a centrifugal force characteristic of its center of gravity. This cyclical force is referred to as balance. On new vehicles, tires are checked in the auto assembly plant upon initial installation and delivery. But when a customer changes or replaces tires, the balance must be recalculated and weights assigned to the wheel to maintain the proper center of gravity. This is performed on a specialized machine by the tire retail shop who sells the replacement tire.If a customer notices his or her vehicle exhibits vibration or shaking of the steering wheel, this could be because one or more wheel and tire assemblies is out of balance. Wheel/tire balance should be checked by a professional tire retailer.

Tire inflation pressure should be checked every month and especially before long trips. To properly confirm tire pressure, motorists should check tires when cold (not been driven on for a period of time). The vehicle manufacturer's recommended pressure is typically found on a plate or label located on the driver's door or door post or within the owner's manual.

Tire Pressure Monitoring System (TPMS) is a system designed and installed by vehicle manufacturers on vehicles to monitor the air pressure inside the tires. The electronic control unit (ECU) in the vehicle receives and evaluates signals transmitted by sensors in each wheel, and will notify the driver if abnormal tire pressure exists. The aftermarket also offers TPMS systems for retrofitting into older vehicles.

Safety Information

The U.S. Department of Transportation (DOT) has developed the DOT Code which is a required series of alphanumeric characters molded into the sidewall of every tire for purposes of tire identification. The DOT Code is especially useful in pinpointing specific tires in the event of a product recall. UTQG is Uniform Tire Quality Grade, a grading system intended to indicate tire characteristics such as tread wear and wet and dry traction capabilities. Mud and Snow, (or M+S, or M&S), are specific winter tires designed to provide improved performance under cold temperature conditions, compared to all-season tires. The tread compound may be softer than that used in tires designed for warmer conditions, which provides better grip on ice and snow, but wears more quickly at higher temperatures. Tires may have higher numbers of sipes in the tread pattern to grip the ice.The All-Season tire is an excellent combination of technology and design enabling a tire to be used on both dry and wet roads, during summer and under challenging winter conditions.

All-terrain tires are commonly used on SUVs and light trucks. These tires have been developed to incorporate stiffer sidewalls for greater strength when traveling off-road, as the tread pattern offers wider spacing than all-season tires to remove mud from the tread.

Many vehicles continue to carry a spare tire already mounted on a wheel, available to replace a flat tire or blowout. In more recent years, auto manufacturers have begun to offer a Minispare, or space-saver tires, which are smaller than normal tires to save trunk space, weight and cost. These space-savers have a short life expectancy, and low speed rating.Some manufacturers have chosen to develop run-flat tire for their vehicles, a specific pneumatic tire designed to resist the effects of deflation when punctured, and to enable the vehicle to continue to be driven, although at reduced speeds (not recommended beyond 55 mph).

Hydroplaning, also known as aquaplaning, is a condition that occurs in wet conditions when the tire tread cannot quickly evacuate enough water to allow for a strong contact patch; this causes the tire to float above the road surface on the layer of water, causing a loss in traction. The effects and frequency of hydroplaning are exacerbated as vehicle speed increases.

All-weather and all-season tires are designed to effectively channel away enough water to ensure a stronger footprint area in wet conditions.

Even unused, research and testing show that as tires age, they begin to dry out and become potentially dangerous. Aged tires may appear to maintain properties similar to newly manufactured tires, but rubber will degrade over time, and once the vehicle is traveling at high speeds (i.e. on a highway or freeway) the tread could peel off, leading to severe loss of control. Thus, retailers must be vigilant about clearing inventories of older tires so they won't be sold to consumers. A date code on the tire sidewall can be used to determine the age of a tire.

Asymmetric tires are typically tires with a tread pattern that is not congruent with a center line; its design does not match consistently throughout the circumference. Thus, the method of mounting tires must be specially prescribed. In many cases, such tires are performance-oriented, in any number of purposes - braking, turning, speed - as tread contact changes according to the change in alignment during travel.

Directional tires are designed in such a way that performance is optimized when the tire is installed rotating a specific direction on a vehicle. Directional tires cannot be rotated from left to right sides of the vehicle unless the tires are dismounted and "flipped" on the wheels.

Service

These functions can be performed directly by the consumer or by an authorized tire retailer:

• Wheel lug torquing - Proper installation requires that the wheel lug torque be set to the recommended specification for your vehicle. Torque specifications may be found in the vehicle's owner's manual, a vehicle's shop manual or directly from the vehicle's dealer/service provider.

Unless specifically stated otherwise, wheel lug torque specifications are for clean and dry threads (no lubricant) that are free of dirt, grit, etc. Adding oil, grease or anti-seize lubricants to the threads will result in inaccurate torque values that may overtighten the wheels. Once lugs are snugged down using proper tools, finish tightening them in a criss-cross pattern with an accurate torque wrench. Overtorquing a wheel can strip a lug nut or hub threads, stretch or break a stud or bolt, and cause the wheel, brake rotor and/or brake drum to distort.

• Bolt pattern -- The bolt pattern is a measurement of the hardware pattern used to secure a wheel/tire assembly on a vehicle. These dimensions will typically be given in a (number of fasteners) x (pitch circle diameter) format, i.e. 5x120.
• Proper lug nuts - Lug nuts are usually either flat, tapered (generally at 60 degrees and referred to as conical seat), or ball seats, meaning the hardware mounting surfaces are flat, tapered, or spherical respectively. Lug nuts must properly fit on the wheel bolt pattern and mounting surface in order to secure the wheel and tire assembly correctly.
• Alloy wheels - Alloys wheels or alloy rims are vehicle (car, motorcycle and truck) wheels made from alloy of aluminium or magnesium metals (or a mixture of both). Magnesium is not commonly used on road vehicles due to potentially limited fatigue life. Aluminum alloy wheels are typically cast or forged, depending on strength, weight, and price point expectations.
• Offset -- The wheel offset, measured in millimeters, can be negative or positive, and is the distance from the hub-mounting surface to the rim's true centerline. A positive offset means the hub-mounting surface is closer to the outside edge of the wheel; a negative offset means the hub-mounting surface is closer to the inside edge of the wheel.
• Wheel size -- The wheel size is the diameter of the wheel, usually in inches, where the beads of the tire seat on the wheel. This measurement does not include the rim flange.
• Tire size -- Modern road tires have specific measurements associated with their size as dictated by tire codes. For a tire that is identified as 255/30R20, the first number in the code (255) represents the nominal tire width in millimeters. This is followed by the aspect ratio (30) which is the height of the sidewall expressed as a percentage of the nominal width. "R" stands for radial and relates to the tire construction. The final number in the code (20) is the rim size measured in inches. It should be noted that the overall circumference of the tire will increase by increasing any of the tire's specifications.
• Valve cap - chrome, plastic or uniquely designed caps that fit any standard threaded tire valve stem intended to protect the valve core from debris and moisture.
• Valve Core - a valve within the valve stem that seals the pressure inside the tire chamber, separating it from external atmosphere. Removal of the valve core will result in rapid depressurization of the tire.

Other Purposes, Choices and Uses

The off-the-road (OTR) tire classification includes tires for construction vehicles such as wheel loaders, backhoes, graders, trenchers, as well as large mining trucks. These tires are built for specific uses and conditions such as heavy loads, dirt, gravel, etc.

Racing tires are highly specialized according to vehicle and race track conditions, including surfaces, cornering loads and track temperatures. This classification includes specific tires for drag racing, autocross, drifting, Time Attack and road racing - as well as high technology, specially engineered race tires for ALMS, Formula One, IndyCar, NASCAR, rallying, MotoGP.

Track or Slick - are tires for track days and/or drag races. Their designs typically have fewer grooves and larger tread blocks, which in turn provide a larger contact patch. When under lateral loads or accelerating from a standing position, track or slick tires are optimized for greater traction though careful selection of tread design and rubber compound. In most cases, these tires are not recommended for the street by manufacturers, and have a shorter life if legally allowed for use on the street.

High performance or Ultra-High Performance (UHP) tires are designed for use at higher speeds, and vehicles with higher speed and cornering capabilities. They feature a specialized rubber compound for improved traction, especially on high speed cornering. The softer rubber compound inherently results in a shorter tread life.