READING A TIRE SIDEWALL
The numbers and letters on the side of your tire have very specific meanings. A tire’s sidewall is pretty much what it sounds like – the outer and inner “walls” on the sides of a tire, if facing a tire on its side. Every sidewall has its own unique information that is divided into three main sections:
1. TIRE SPECS
This describes the fundamental characteristics of your tire. Size, construction, speed rating and more.
- TIRE TYPE This designates the type of vehicle the tire fits. P is for passenger metric. Other letters are LT (for light truck), T (for temporary spare) and ST (for special trailers). If your tire has no letter, it signifies that your tire is a euro “metric” size.
- TIRE WIDTH Also called Section Width, this is the width of the tire (or thickness) in millimeters, if measured from a tire’s widest point of its outer sidewall to the widest point of its inner sidewall. Why millimeters? It originated in Europe, which uses the metric system.
- ASPECT RATIO This identifies the tire’s aspect ratio, which is the relationship of the tire’s sidewall height to the tire’s width. In this example, the sidewall height of the tire is 55% of its width. The lower the ratio, the smaller the sidewall height, which means better cornering, but a rougher ride.
- CONSTRUCTION This is the tire’s internal construction, which is “radial.” Almost every tire on the road has radial construction, which means the cords of the carcass plies inside the tire “radiate” directly across from one side of the tire to the other. Other letters used are D, for diagonal construction, and B, for belted.
- WHEEL DIAMETER This number (in inches) indicates that the tire is designed to fit on a wheel with a 18-inch diameter.
- LOAD INDEX This indicates how much weight the tire is certified to carry at maximum safe inflation. It doesn’t mean 97 pounds, because it’s actually an assigned value that corresponds with its “actual” load capacity found on a load index chart. If you look up 97 on the chart, you’ll find 1,609 pounds.
- SPEED RATING This indicates the maximum safe speed at which a tire is certified to carry a load under specified conditions. Speed ratings range from A (lowest) to Y (highest), with one exception: H falls between U and V. To find the maximum speed for your tire, refer to the speed rating chart*. Exceeding the lawful speed limit is neither recommended nor endorsed.
This assures that your tire complies with all Department of Transportation (DOT) safety standards. After the DOT insignia is your tire’s identification number, which begins with the tire’s manufacturer and plant code where the tire was manufactured (two numbers or letters). The ninth and tenth characters tell the week the tire was manufactured. The final number(s) signifies the year the tire was manufactured.
3. UTQG CODE
The Uniform Tire Quality Grading (UTQG) was established by the National Highway Traffic Safety Administration (NHTSA) to test tires following government prescribed test methods and then grade each tire on three main components:
- Treadwear: This is the wear rate of the tire, comparable only to other tires within a tire manufacturer’s line. 100 is the baseline grade. Therefore a tire with 200 would theoretically last twice as long on the government’s course compared to a tire with 100.
- Traction: Traction grades are AA, A, B and C (with AA being the highest grade). They represent the tire’s ability to stop straight on wet pavement as measure on a specified government track. Any tire rated under C is considered unacceptable for road travel.
- Temperature: The temperature grades, from highest to lowest, are A, B and C. These represent the tire’s ability to dissipate heat under controlled indoor test conditions. Any tire rated below C is considered unacceptable.
Some tires have unique benefits, as showcased with specific icons. For example, a Mountain Snowflake symbol tells you that the tire meets or exceeds industry-established snow traction performance requirements.
HOW TO CHECK TIRE PRESSURE
Discover the importance of air pressure and how to measure it. Believe it or not, tires can actually lose up to 1psi (pounds per square inch) every month. So be on the safe side and check all tires, including your spare, once a month (or before a long trip). It’s no biggie. Here’s how you do it:
- Purchase a trusted pressure gauge.
- Check your tires “cold” – before you’ve driven or at least three hours after you’ve driven.
- Insert pressure gauge into the valve stem on your tire. (The gauge will “pop” out and show a measured number. When you hear a “pssst” sound, that’s air escaping the tire. The escaping air shouldn’t affect pressure substantially, unless you hold down the air pressure gauge too long.)
- Compare the measured psi to the psi found on the sticker inside the driver’s door of your vehicle or in owner’s manual. DO NOT compare to the psi on your tire’s sidewall.
- If your psi is above the number, let air out until it matches. If below, add air until it reaches the proper number.
It’s pretty common knowledge that most tires are filled with compressed air. But some tire dealers have started putting nitrogen in their customers’ tires. (Nitrogen is simply dry air with the oxygen removed. Air contains nearly 79% nitrogen already. Note: Welcome to science class.) Because nitrogen replaces oxygen, less air can escape your tires, and your air pressure stays higher for longer. Also, know that nitrogen and compressed air CAN be mixed, if needed.
Unfortunately, there are other possible sources of leaks (tire/rim interface, valve, valve/rim interface and the wheel), which prevent the guarantee of pressure maintenance for individuals using air or nitrogen inflation. Tires manufactured by BFGoodrich Tires are designed to deliver their expected performance when inflated with air or nitrogen, as long as, the user respects the pressures recommended by the vehicle manufacturer on the vehicle’s placard or by the tire manufacturer.
HOW TO INSPECT A TIRE
One of the most useful tools in the tire industry is right at your fingertips. Once every month, or before you embark upon long road trips, check your tires for wear and damage problems. One easy way to check for wear is by using the penny test. All you have to do is grab your spare change and follow 3 easy steps.
1. Take a penny and hold Abe's body between your thumb and forefinger.
2. Select a point on your tire where tread appears the lowest and place Lincoln's head into one of the grooves.
3. If any part of Abe Lincoln's head is covered by the tread, you're driving with the legal and safe amount of tread. If your tread gets below that (approximately 2/32 of an inch), your car's ability to grip the road in adverse conditions is greatly reduced.
TIRE ROTATION
You’ve heard about rotation. During rotation, each tire and wheel is removed from your vehicle and moved to a different position to ensure that all tires wear evenly and last longer. Tires should be rotated every six months or 6,000 to 8,000 miles.
TIRE BALANCE
What is tire balancing and why do you need it? Tire balancing is pretty much what it sounds like. It compensates for the weight of the tire and wheel assembly after the tire is mounted. A wheel is out of balance when one area is heavier or lighter than the rest. That causes bouncing or wobbling, which can decrease treadwear, increase vibration and cause stress on your vehicle. The cure? Correction weights are added to counterbalance the tires.
WHEN TO BALANCE
- A tire is replaced
- A balance weight is moved or removed
- You purchase new tires
Balancing a wheel is pretty cool process. First Choice Wheels and Tires uses a high-tech balancing machine to determine where the heavy spots are. Weights are then attached to the exterior or interior of the wheel to counteract centrifugal forces acting on the heavy areas when the wheel is turning. This will eliminate vertical bouncing and side-to-side wobble.
TIRE ALIGNMENT
If you’re talking about alignment, you’re talking about the adjustment of a vehicle's front and rear suspension parts. And it needs to be correct. If the alignment is off, the vehicle isn’t safe to drive.
- CASTER
Caster is a bit tough to define. If you're viewing the side of a vehicle, the caster angle identifies the forward or backward slope of a line drawn through the upper and lower steering pivot points. Think of a motorcycle and its front steering forks and front tire. Its angle is towards the rear of the motorcycle, so it has positive caster. Negative is just the opposite. Long story short, positive caster helps your vehicle go straight, much like the motorcycle. - CAMBER
Camber is the angle of the wheel, in degrees, when viewed from the front of the vehicle. Positive camber is when the top of the wheel is leaning out from the center of the car. Negative camber is when the top of the wheel is leaning into the car. If the wheel leans too far from the center, uneven wear will occur. (However, negative camber helps racing cars improve cornering.) - TOE
Toe is the difference in the distance between the front of the tires and the back of the tires. Usually, tires are set so that they are parallel with each other. If the fronts of the tires are closer, the wheels are toe-in. If the rears of the tires are closer, the wheels are toe-out.
Yes, those never-ending potholes and bumpy railroad crossings are seriously annoying. But they, along with more severe circumstances like a car accident, can knock your vehicle out of alignment. So, be sure to have your alignment checked if :
- You’ve hit something substantial
- You see a wear pattern developing on the shoulders (outer edges) of the tires
- You notice a difference in your vehicle’s handling
There’s a right way and wrong way to wash your tires. Nothing makes a car look sweeter than a shiny set of tires. But don’t put your investment at risk by using just any cleaner. Make sure to only use acid-free products. A number of wheel cleaners may contain harsh acids, alkalis and/or detergents that can damage wheels and paint. However, there are products out there that are safe for all brands of tires as well as environmentally responsible. You can find them at an auto parts dealer near you.
Read this and more at First Choice Wheels and Tires
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