Is allways good to know.....

Tires are one of the most important components of the vehicles when we are talking about our safety and the perfomance of the car. Tires has to do a lot with MPG or Miles per Galon on our car and the safety level we have when driving in different conditions. Knowing a little bit about tires, will give us enough knowledge when buying or using a tire.

Comtires Mission is not only sell Tires, Wheels and Services but to Offer a Good Customer Service, in other words, we want to enhance the safety on our Customer's driving, maximize the performance of their vehicles and protect their budget.

Safety begins with knowldege, so place take a time to read the next paragraphs about Tire's Basic Knoeledge.

Tire Balancing, What for?

Every time a wheel is first mounted onto the axle with a new tire, it has to be balanced. The goal is to make sure the weight is even around the axle. Wheel balance is checked on a wheel balancing machine that can sense as little as 1/4 ounce difference in weight around the wheel. Why worry about 1/4 ounce on a wheel that weighs many pounds? That tiny amount of weight is traveling very fast around the axle: hundreds of times a minute. It creates enough momentum to cause serious vibration. And when you multiply by 4 wheels, the wobble really adds up. Unbalanced tires put uneven pressure on the treads. Tires get too hot and wear unevenly. Tire imbalance can also strain the wheel bearings and suspension system.

To balance the tires, the technician places tiny offsetting weights at specific points around the wheel. Not "once and done". The minute you pull away from the service station with your newly balanced tires, they begin getting out of balance again. Every bump and corner affects balance; so does tire wear. Over time, your tires get out of balance again. That's why it's important to have tires balanced regularly.

What are the warning signs that my tires aren't balanced? You're most likely to notice uneven wear on the tires. Many drivers also notice vibration over 40 mph, especially if the imbalanced tires are on the front.

How often should my tires be balanced? During typical use, it's a good idea to have your tires rotated and balanced every 4,000 to 6,000 miles. Have them balanced any time a tire is replaced or patched.

Speed Rating and Load Rating

The speed rating tells you the speed the tire can safely maintain over time. A higher speed rating usually means you will have better control and handling at higher speeds - and that the tire can take the extra heat. As a general rule, tires with higher speed ratings also handle better at slower speeds.

The U.S. Department of Transportation (DOT) set the ratings scale, shown below. But tire makers test their own tires and assign their own speed ratings. On the sidewall of every tire, you'll find one of these speed rating codes:

M - Up to 81 mph
N - Up to 87 mph
P - Up to 93 mph
Q - Up to 99 mph
R - Up to 106 mph
S - Up to 112 mph
T - Up to 118 mph
H - Up to 130 mph
V - Up to 149 mph
W - Up to 168 mph
Y - Up to 186 mph
Z - (See Below)

What does 'Up to 99 mph' really mean? Tires with a Q speed rating can safely sustain speeds of up to 99 miles per hour. The tire may be able to reach higher speeds, but going faster than 99 mph for any length of time is not safe. The tire is not designed to handle the stresses.

What is a Z Rating? For tires rated above 149 mph, a Z rating may appear in the size designation.

Safety and Speed Ratings

When you get new tires, choose tires with at least the speed rating your car or truck's manufacturer recommends. It's ok to move up to a higher speed-rated tire, but don't go lower.
The speeds shown are test speeds; they are not recommended speeds. Please obey speed limits. We want you to be safe

Are you hauling groceries - or bricks? The Load Rating or Load Index indicates how much weight each tire can safely support. Every tire's load rating is stamped into its sidewall, usually after the words "Max Load". Sometimes this will be given in pounds (lb) or kilograms (kg), but it is often given as a rating code — a number between 71 and 110.

If your tires have this code, you can use the chart below to see how much weight each tire can support. Then multiply the weight by four - or the number of wheels on your car or truck. That's how much your tires can safely carry.

When you get new tires, make sure they have the same or higher load rating than the tires that came on the car or truck when it was new.

UTQG

When we are lookig for new tires to buy, our first concern is safety and performance. Then we wonder about the traction capacity and the Design or Tread durability. How are we going to feel the road and the grip of the tires.

Here's something we can use:

The Uniform Tire Quality Grading (UTQG) system was developed by the Department of Transportation (DOT) to assist consumers in the purchase of their tires by providing a standard grading system used by all tire manufacturers. Tire manufacturers use the UTQG system to grade their tires in three important areas: treadwear, traction and temperature. The UTQG grade for each tire is molded in the sidewall.

Treadwear Grade – A comparative grade based on the actual wear of the tire’s tread when tested under specific controlled conditions. All tires are tested under the same conditions to allow for comparison between manufacturers and between different lines of tires from the same manufacturer. The system is fairly easy to understand. A tire with a treadwear grade of 400 should have a useful tread life approximately twice as long as a tire with a treadwear grade of 200. The higher the grade, the better the expected treadwear.

Traction Grade – A comparative grade based on the tire’s ability to stop on wet pavement, again as measured under controlled conditions on wet asphalt and concrete surfaces. The grades, from highest to lowest, are designated AA – A – B – C. A tire that is graded AA should have better traction or stopping performance than a tire with a lower grade, based on the specific straight-ahead braking tests.

Temperature Grade – A comparative grade based on the tire’s resistance to heat and its ability to dissipate heat, again as measured under controlled conditions. The grades, from highest to lowest, are designated A – B – C. An A-rated tire is the coolest running, while a C-rating meets the minimum federal performance standards. These temperature grades are set based on a tire that is properly inflated and not overloaded.

UTQG is a great way to compare tires from various manufacturers and between specific lines from the same manufacturer. Remember: The UTQG isn’t a safety rating and it doesn’t guarantee a tire’s mileage performance - but you can use the UTQG in conjunction with price, warranty, appearance and recommendations to make the right tire choice for your needs.

What are all the letters, numbers and symbols on the Tire Sidewall?

Each of your tires has useful information molded right into its sidewall. You’ll find the tire’s brand, size, construction details, maximum load and inflation pressure, as well as traction, treadwear and temperature grades. The trick is knowing where to look. The diagram below will help you make sense of your tire’s sidewall:

Passenger Tires. The tire sidewall shown above is an example of a popular “P-metric,” speed-rated tire. “P” indicates that it’s a passenger tire; 215 represents the width of the tire in millimeters; “65” is the height to width ratio; “R” indicates radial construction; “15” is the rim diameter code; and “95H” is the optional service description that consists of the load index (95) and the “H” speed rating. “Temperature A” reflects the temperature grade. Some older speed-rated tires may include the speed symbol immediately before the “R” instead of providing a service description. A “B” in place of the “R” would indicate diagonal bias construction. “M+S” with the mountain/snowflake symbol indicates that the tire meets the RMA (Rubber Manufacturers Association) specifications for use in severe snow conditions. The maximum load recommendation is shown in kg (kilograms) and in lbs (pounds), and the maximum air pressure is shown in kPa (kilopascals) and PSI (pounds per square inch). Safety Note: These are the maximum air pressure levels, not the recommended pressure for the tire when mounted on rims for your vehicle. The vehicle manufacturer’s pressure recommendations (found on a decal on the doorjamb or in the glove compartment) must always be used when inflating your tires.

The DOT Code and Your Safety. The “DOT” letters indicate manufacturing compliance with all applicable safety standards established by the U.S. Department of Transportation (DOT). Next to the DOT letters is an alpha/numeric serial number, commonly referred to as the DOT Code, with up to 12 digits. This code provides manufacturer detail and the last 5 numbers indicate the week and year that the tire was made. For example, “1501” indicates that the tire was manufactured during the 15th week of year 2001. This information is critical should there ever be evidence of a manufacturing problem and a tire recall.

Additional Tire Size and Capacity Information. There are other codes on some tires that provide you with additional information, some of which are specific to light truck tire applications. Some of the other codes that you might find on your tires include:

LT = Stands for light truck application. Example: LT235/85R16

C, D or E = Load range indication for light truck applications

REIN = Reinforced

OWL = Outlined White Letters

RWL = Raised White Letters

ORWL = Outlined Raised White Letters

B, BLK, BW, BSW = Blackwall or Black Sidewall

W, WW, WSE – Whitewall or White Sidewall

XNW = Extra Narrow White Width

XL = Extra Load Capacity

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