Auto Tires - What to Know about Car Tires & Truck Tires

Tires are possibly the most expensive routine maintenance item for any vehicle. It's not unusual for a set of tires to cost more than $600 for an SUV or pickup truck, but if you have unique tires on your car, you can see price tags well beyond that. Let's take a look at the following topics to help you save on auto tires: tire sizes, when to buy tires, tire features, tires needed by car type, caring for tires and buying tires.

TIRE SIZES

General information

Tire sizes are displayed as an equation of the tire's treadwidth and sidewall measurements.

• Treadwidth: horizontal measurement of the tire's tread
• Sidewall: external part of the tire between the rim and the tread

A typical tire size looks something like this: 205/60-15. The first number is the treadwidth in millimeters. The second number is the sidewall height of the tire expressed as a percentage of the treadwidth.

In this example, the height of the sidewall of the tire is 60 percent of the treadwidth, so the tire in this example has a sidewall height of 205 X 0.6 = 123 millimeters. So, as the second number gets smaller, the height of the sidewall gets lower.

The last number is the size of the wheel on which the tire fits. In this case, 15 means that the tire fits a 15-inch wheel.

The height of the sidewall is important to note because the taller it is the softer the tire will ride, which means you will feel less bumps in the road. Traditionally, soft-riding luxury cars have tires with tall sidewalls. Generally speaking, taller sidewalls are more comfortable and lower sidewalls are more sporty.

Special Tire Sizing

If you have a pickup or SUV, you should probably go with light truck (or "LT") tires. These usually have only the first and last numbers, so they are sized something like 235-15LT. That means it is a light truck tire that is 235 millimeters wide and it fits on a 15-inch wheel. Light truck tires usually do not have any options for sidewall height -- to change sidewall height on a truck, you usually must buy passenger car tires.

Light truck tires are recommended for a pickup or SUV. If you have a small pickup or SUV (such as a Ford Escape, Chevy S-10, Honda CR-V, etc.) and never take it off the road, then you can use a passenger car tire.

Passenger car tires generally are quieter and more comfortable than light truck tires. However, you can not go off the road with passenger car tires and you should not plan to run the truck frequently at maximum load with passenger car tires.

If you have a mid- or full-size pickup/SUV, always use light truck tires unless the vehicle's manufacturer approves otherwise.

WHEN DO I NEED TIRES?
Tires are considered worn out when they have less than 1/16-inch of tread remaining. Most modern tires have wear bars that run across the tread, so a tire is worn when the wear bar is even with the tread. In most cases, tires will make a roaring noise when the tires are worn.

WHAT ARE THE FEATURES OF TIRES?

Tires have a great deal to do with the performance and comfort of your car. The best tires for you will give your car the handling, braking performance, traction and ride comfort that you want. If you're happy with your current tires then buy another set of tires just like them. Buy the same brand, model and size, unless that exact tire is no longer made. Sadly, this happens all too often.

If you're shopping for a new set of tires and don't want the exact same ones as those now on your car, then there are several things that you need to consider when you go shopping:

UTGQ Ratings
The UTQG (Uniform Tire Quality Grading) system rates tires for treadwear, traction, temperature.

• Treadwear: A tire rated 200 for treadwear will have twice the life of a tire rated 100. There is no intended correlation between the treadwear number and the number of miles that you will get from a tire.
• Traction: This rating is for the tire's braking traction on wet pavement, NOT the traction during cornering or acceleration. The traction rating also says nothing about a tire's ability to handle snow or ice. In fact, there is no measurement or rating that's widely used to quantify a tire's ability to handle icy conditions. Traction can be rated AA, A, B or C, with AA being the highest rating and C being the lowest rating.
• Temperature: This measures the tire's ability to withstand the effects of heat during high-speed driving. Temperature can be rated A, B or C, with A being the highest rating and C being the lowest rating.

Keep in mind that tire manufacturers test tires for their UTQG ratings, not the government. This means you should not place undue confidence in UTQG ratings. Still, all things considered, you want to get tires with the highest UTQG ratings possible, as long as they are within your budget and appropriate for your car.

Speed rating

The tire's speed rating must be considered when shopping for a new set. A tire's speed rating represents the tire's speed capability - or the maximum speed it can handle on the road.

Most passenger car tires are rated "S" or "T" for speed, while performance tires have speed ratings such as "V" and "Z." Here's what these letters mean with respect to the maximum speed rating for a tire:

Designation              Speed
Q                              99
R                              106
S                              112
T                              118
U                              124
H                              130
V                              149
W                             168
Y                              186

Sometimes tire manufacturers use the letters VR to indicate a maximum speed capability of more than 149 mph. Tire manufacturers always use the letters ZR to indicate a maximum speed capability of greater than 186 mph. Note that a tire with a speed rating of "H" has a higher speed performance rating than a tire rated "T."

The speed rating of a tire also gives some indication of the tire's sidewall stiffness. Tires rated with speed ratings of H and higher generally have a stiffer ride than tires with lower ratings. On the other hand, these tires also almost always have better cornering characteristics. So, if you want a sportier ride and crisper handling, get tires that have speed ratings of H, V, W and Y. If you want a softer ride and average handling, get tires with speed ratings of S and T.

Pressure Rating

Tire manufacturers rate each model tire for the maximum amount of pressure that the tire can withstand. Most modern tires have a maximum pressure rating of at least 35 pounds per square inch (psi), which means that you can inflate the tires to 35 psi without exceeding the tire manufacturer's rating. Your vehicle's manufacturer almost certainly has listed its recommended tire inflation levels for your specific car. There will be a sticker on the frame of the driver's door listing the car manufacturer's recommended tire inflation.

Tires today have ever higher maximum tire inflation ratings -- it's common today to see tires rated for 44 psi and some are rated at 51 psi. This is important because the higher your tires are inflated, the better your car's gas mileage will be.

If you have a taller vehicle, such as an SUV or a four-wheel drive pickup, then stick with the manufacturer's recommended inflation. If you have any questions, go to a dealer and ask the service department for advice.

On the other hand, if you have a passenger car that has a normal height from the ground, it's safe to inflate the tires to within two psi of the maximum. This recommendation is for passenger cars ONLY. Trucks should always be inflated according to the manufacturer's instructions.

Run-flat tires

Run-flat tires enable a driver to continue driving with a punctured tire at reduced speeds and for a specific amount of miles - usually 100 to 200 - before the tire must be changed. They're meant to give drivers the opportunity to get to a gas station or other locale for assistance. There is nothing worse than changing a tire in the rain or dark!

Run-flat tires are safe but they are very expensive to replace (some can cost more than $1000 with labor) and not all tire shops have the equipment to replace them. Also, if you have run-flat tires, you probably don't have a spare tire, so keep that in mind when thinking about buying run-flat tires. If one gets shredded, you will not have a replacement and will be stuck where your tire blew.

Run-flat tires are a mixed blessing.

Rolling Resistance

The rolling resistance measures how easy it is to roll a tire down the road. Different tires have different rolling resistances, so some tires are easier to roll than others. Easy rolling means that you will get better gas mileage with that tire, and that's a good thing. (Running a tire at a higher inflation will almost always make it easier rolling -- that's one reason why gas mileage improves.) Unfortunately, there is no widely advertised rating for rolling resistance, so you are at the mercy of a tire dealer when it comes to discussing rolling resistance.

WHAT DO I NEED FOR MY CAR?

When you shop for tires, you should know the following:

• Your tire size
• Whether you want a standard passenger car tire, a light truck tire or a performance tire
• Whether you need "Mud & Snow" (M&S) rated tires, usually abbreviated as M&S

For a better deal, look for the following:

• Tires that have a higher pressure rating so that you can inflate them higher and get better gas mileage.
• Tires that are narrower and taller - it's another way to improve gas mileage.
  • However, taller and narrower tires will have more vague handling and not feel as "sporty."

HOW DO I CARE FOR TIRES?

Here are some easy tips to following for auto tire maintenance.

1. Once a month, take a look at your tires (front AND rear) and check for wear. 1/16-inch is not very much tread, so if the tire looks nearly bald, it's time for new tires.
2. Follow the car manufacturer's recommendations for rotating tires, which distributes the wear evenly for front and rear tires.
3. Check inflation once a month and keep the tires at their recommended inflation level. It will give you longer tire life and better gas mileage.
4. Check for worn suspension and steering components (shock absorbers, struts, etc). Poor wheel alignment also wears tires out quickly.
5. Don't carry too much in your car - if you can help it. If you ordinarily carry around more stuff than you really need, you are wearing your tires faster than normal. In addition, the extra weight reduces your gas mileage and makes your car handle below normal.

WHERE CAN I BUY TIRES?

Car dealers
Try places like Goodyear, Firestone or other independent tire shops. Many Sears and Walmart stores sell tires, as do auto parts stores such as Pep Boys and Autozone. Check advertising fliers carefully for good deals and you can find a good price at any of these stores. Building a relationship with a good tire dealer is a good thing, as a smart organization will want you do come back and buy again. A good dealer will take care of you.

Warehouse clubs
Sam's Club and Costco are downright bargains for tire labor, usually charging MUCH less for labor than more mainstream tire dealers. Warehouse clubs often have access to better tire warranties or other extras, such as free tire rotations.

Online
If you have specialty tire needs, such as an unusual "run-flat" tire or a high-performance car, then try a mail order/Internet company called The Tire Rack. Not only does The Tire Rack have excellent prices and terrific online information, it can ship tires to you in a day or two.

SUMMARY
Tires are complex things that we generally give little thought to over the years. If you need new tires, find out what size you need and study the above material about the UTQG. Make a decision about comfort vs. performance, and decide which retailer is right for you.

Shop carefully and ask questions... and keep ‘em rollin'!