Tires—Your Life Could Depend on Them!
IMAGINE being strapped inside a welded steel-and-glass cage with acid and flammable liquids in containers near you. Now suspend this potentially deadly construction just inches off the ground and accelerate it to about 100 feet per second [30 m/sec]. As a final touch, put your machine among similar ones and have them dart around one another while other machines race past you from the opposite direction!
That is essentially what you do every time you get into a vehicle and drive down the highway. What helps you to maintain control and feel secure while driving? To a large degree, it is your tires.
What Tires Do
Tires serve a variety of important purposes. They not only bear the weight of your vehicle but also cushion it from bumps, potholes, and other irregularities in the road. More important, your tires supply vitally needed traction in order for you to accelerate, steer, brake, and provide directional stability under varying road conditions. Yet, only a small portion of the tire—about the size of a postcard—is in contact with the ground at any one time.
In view of their importance, what can you do to keep your tires functioning safely and efficiently? And when the time comes, how do you select the correct tires for your vehicle? Before answering these questions, let us take a brief look at the history of the tire.
Early Pioneers of Rubber
Although wheels have been in use for thousands of years, the idea of attaching rubber to the outer rim of vehicle wheels is a relatively recent development. Natural rubber was first attached to wooden or steel wheels in the early 1800’s. But it wore out quickly, so the future of rubber-coated wheels seemed bleak—that is, until Charles Goodyear, a determined inventor from Connecticut, U.S.A., came along. In 1839, Goodyear discovered a process known as vulcanization, whereby rubber is infused with sulfur, under heat and pressure. This process made the rubber much easier to mold and vastly improved its resistance to wear. Solid rubber tires became more popular, but they gave a rough ride.
In 1845, Scottish engineer Robert W. Thomson received a patent for the first pneumatic, or air-filled, tire. However, it wasn’t until another Scotsman, John Boyd Dunlop, set out to improve the ride of his son’s bicycle that the pneumatic tire became a commercial success. Dunlop patented his new tire in 1888 and started his own company. Nevertheless, the pneumatic tire still had to overcome significant obstacles.
One day in 1891, a French cyclist got a flat tire. He attempted to repair it but failed because the tire was permanently bonded to the bicycle wheel. He sought the help of a fellow Frenchman, Édouard Michelin, who was known for his work with vulcanized rubber. Michelin spent nine hours repairing the tire. That experience motivated him to develop a pneumatic tire that could be removed from its wheel for easy repair.
Michelin’s tires were so successful that the following year 10,000 happy cyclists were using them. In short order, pneumatic tires were installed on horse-drawn carriages in Paris, much to the delight of their French passengers. In 1895, to demonstrate that pneumatic tires could be used on motorized vehicles, Édouard and his brother, André, put them on a race car, but it finished last. Still, people were so amazed by these unusual tires that they tried to cut the tires open to see just what the Michelin brothers had hidden inside them!
In the 1930’s and ’40’s, durable new materials, such as rayon, nylon, and polyester, replaced the more fragile materials of cotton and natural rubber. Following World War II, groundwork was laid for a tire that maintained an airtight seal directly against the wheel, therefore no longer requiring an inner tube to contain the air. Later, further improvements were made.
Today, over 200 raw materials go into making a tire. And with the help of modern technology, some tires boast a life span of 80,000 miles [130,000 km] or more, while others can endure speeds of hundreds of miles per hour on a race car. All the while, tires have become more affordable for the everyday consumer.
If you own a motor vehicle, you may be faced with the daunting task of selecting new tires. How do you determine when it is time to replace your tires? By inspecting your tires regularly for obvious signs of wear or damage.* Tire manufacturers provide built-in wear indicators, frequently called wear bars, to indicate when your tires have reached the end of their useful life. Wear bars appear as solid bands of rubber across the tread surface. It is also good to check for tread separation, protruding wires, bulges in the sidewall, and other irregularities. If you find any of these things, you should not drive the vehicle until the tire is repaired or replaced. If you purchased the tires new, the tire retailer may replace the damaged tire at a reduced cost if it is covered by a warranty.
Tires are best replaced in matched pairs, mounted on the same axle. If you are installing only one new tire, mate it with the tire having the most tread in order to balance traction when braking.
Sorting through all the different types, sizes, and models of tires can be confusing. However, by answering a few key questions, you will find the job to be much easier. First, review the vehicle manufacturer’s recommendations. Your vehicle has specific requirements that need to be considered, such as tire and wheel size, ground clearance, and load capacity. Important, too, is your vehicle’s design. Modern vehicles with antilock brakes, traction control, and all-wheel-drive systems are designed to be used with tires having specific operating characteristics. Tire specifications are usually found in your vehicle owner’s manual.
Another factor is road conditions. Will your vehicle be driven mostly on dirt or paved roads, in rainy or dry weather? It could well be that you drive under varying conditions. In that case, you may need all-terrain or all-season tires.
You should also consider the life expectancy and traction rating of the tire. Generally, the softer the tread compound, the more traction the tire will have, but it will wear out sooner. Conversely, if the tread compound is relatively hard, the tire will have less traction but will likely last longer. Ratings are usually found in sales literature where tires are sold. Be aware that tire ratings vary from manufacturer to manufacturer.
Once you have narrowed down your search, price may determine your final selection. Well-known manufacturers usually offer better quality assurance and warranty coverage.
Maintaining Your Tires
Proper tire maintenance involves three things: maintaining the correct air pressure, rotating the tires regularly, and keeping them properly balanced and aligned. Maintaining the correct tire pressure is very important. If a tire has too much air, the tread will wear prematurely in the center. On the other hand, if tire pressure is too low, a tire will wear excessively on the edges and fuel efficiency will be reduced.
Tires may lose a pound [0.5 kg] or more of pressure every month because of air bleeding through the rubber. So don’t assume that you can tell whether your tires are properly inflated by looking at their shape. According to the Rubber Manufacturers Association, “a tire can lose up to half of its air pressure and not appear to be flat!” Therefore, use a pressure gauge to monitor tire pressure, and do so at least once a month. Many vehicle owners keep a gauge in the glove compartment for convenient use. Always check your tires when you change the engine oil and only when the tires are cold—in other words, after they have been sitting for at least three hours or when they have been driven on for less than a mile [1.5 km]. Tire pressure specifications are usually noted in the owner’s manual, on a label near the driver’s doorpost, or in the glove compartment. If you want to avoid a rough ride, do not inflate tires to the maximum pressure, which is molded on the sidewall.
Tires will last longer and wear more evenly if you rotate them on a regular basis. Unless your vehicle manufacturer recommends otherwise, it is good to rotate tires every 6,000 to 8,000 miles [10,000 to 13,000 km]. Once again, check your owner’s manual for the suggested rotation pattern.
Finally, get your tire alignment checked annually or whenever you notice any unusual vibration or irregularity in your car’s steering. While the suspension system on your vehicle is designed to align the tires under varying loads, normal wear and tear makes it necessary to check and realign the tires periodically. An automotive service technician who is certified in suspension and wheel alignment should be able to keep your vehicle in accurate alignment, maximizing tire life and ride quality.
With the aid of computers, some cars warn the driver when tire pressure is below safe limits. Some tires can operate safely for short periods without air pressure, and others seal themselves after a puncture. Indeed, engineers are designing tires for an ever-widening range of operating conditions.
As advances in materials, tread design, suspension, steering, and braking systems are applied to modern vehicles, tires make driving not only easier but safer.
See the chart on page 21 for help in inspecting your tires.
[Chart/Pictures on page 21]
Tire Maintenance Checklist
□ Are there bulges in the sidewall?
□ Are wires showing in the tread surface?
□ Is the tread depth within safe limits, or are the tires’ wear bars showing?
□ Is the tire pressure set at the vehicle manufacturer’s recommended pressure?
□ Is it time to rotate the tires? (Use the vehicle manufacturer’s suggested mileage interval and rotation pattern.)
□ Should different tires be installed because of a change in seasons?
[Diagram on page 20]
(For fully formatted text, see publication)
Parts of a Tire
Tread provides traction and cornering grip
Belts stabilize and strengthen the tread
Sidewall protects the side of the tire from road and curb damage
Body ply gives the tire strength and flexibility
Inner liner keeps the air inside the tire
Bead assures an airtight fit with the wheel
[Pictures on page 19]
An early bicycle and car, both with inflatable tires; workers at an early tire factory
The Goodyear Tire & Rubber Company