We get asked from time to time ” what do all the marking on the tire sidewall mean” or “I don’t know how to read the tire sidewall?.” So we decided that we would write a article to help people interested in learning more about their tires
Have you ever been curious about the letters and numbers on your tire’s sidewall? These provide important information, especially when it comes to the tire’s size. In addition, the sidewall numbering will also give you a better idea about the performance of the tire and its durability.
Installing the right tires on your vehicle is obviously of uttermost importance. This is why you can’t leave the purchase of new tires to chance. Your vehicle’s owner manual will give you enough information about the right tire size. Once you know what you’re looking for, you can pay attention to the sidewall information and make sure that the manufacturer’s requirements are met.
Where to Look for Tire Size Information.
Before learning what the letters and the numbers on the tire mean, you’ll need to learn where to find all of the important information.
Regardless of the vehicle you drive and the size of tires you need, the information will always be available at the same spot. The sequence of numbers and letters is usually available on the tire’s sidewall. You can also get data about the correct tire size in the driver’s side doorjamb, the gas tank hatch and the glove box door. The same sequence of letters and numbers will have to be printed on all of those spots.
Once you’ve located the number, you’ll need to move on to the next step – namely, figuring out what the code means.
How to Read the Tire Size Information
The series of letters and numbers on the tire’s sidewall will provide a lot of essential information. Here’s how you should decode the number sequence:
The first letter: it will be either a P or an LT. P stands for passenger vehicle and LT refers to light truck tires. Obviously, if you own an automobile, the code will begin with a P.
Three-digit number: the three digit number that follows the first letter is indicative of the tire’s width. The width is presented in millimeters and it refers to the measurement taken from one tire sidewall to the other.
Two-digit number: that follows the width data: after you read the three-digit width code, you’ll come across the next number that consists of two digits. This number refers to the aspect ratio – how tall your tire profile is. The aspect ratio is a percentage. It is calculated by dividing the tire’s height by its width. An aspect ratio of 75 percent, for example, means that the tire’s height corresponds to 75 percent of its width. A lower aspect ratio is usually correlated to better vehicle handling on the road.
- Construction letter: the aspect ratio number is followed by yet another letter, which refers to construction. This letter refers to the type of internal tire construction. The letter could be either R (radial) or D (diagonal). Most tires tend to have radial construction.
- Rim diameter number: the two-digit number following the construction letter is known as the rim diameter number. It’s provided in inches.
- Load index: this is a very important number because it suggests how much load the tire can handle when fully inflated. This is an index value and each one corresponds to a certain load capacity. The numbers in the index range from 1 to 155 with one representing 99 pounds of weight and 150 representing 7385 pounds.
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- Speed rating: the final letter in the sidewall sequence is known as the speed rating. A tire that has a speed rating of S is rated for good performance at speeds of up to 112 miles per hour. R refers to good performance at speeds of up to 106 miles per hour. Tires that have a higher speed rating are usually characterized by better handling. When looking for new tires, make sure that the speed rating is the same or higher.
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Other Markings and Tire Sidewall Information
Apart from the standard range of letters and numbers, a tire’s sidewall could contain some additional information. It includes the US Department of Transportation markings and the Uniform Tire Quality Grading markings.
The US Department of Transportation marking comes in the form of a DOT number. The DOT number stands as evidence that the tire has passed the minimum Department of Transportation requirements for sale in the US. The number consists of two components – the code of the manufacturer and the code of the facility where the tire was manufactured.
The DOT code also contains information about when the tire was manufactured. A code that ends with 1015 means that the tire was manufactured on the 10th week of 2015.
Uniform Tire Quality Grading markings refer to several other important pieces of information. These include the tire’s treadwear rating, the traction rating, temperature rating, maximum inflation pressure and load:
- Treadwear rating: this one provides information about just how durable the tire is. To locate this number, look for the word Treadwear on the wall – it should be followed by a three-digit number. A tire that has a treadwear number of 200 will last twice as much as the industry’s standard time.
- Traction rating: it comes in the form of a letter combination like AA, A, B or C. This number refers to the tire’s traction rating when braking in a straight line on a wet surface. AA and A are the numbers that are indicative of the best performance.
- Temperature rating: this letter represents the tire’s ability to withstand heat at a high speed. The temperature rating comes in the form of a grade with A being the best and C being the worst.
- Maximum inflation pressure and load: this number usually comes in the form of 50 PSI, for example. It refers to the maximum air pressure that the tire can hold. It’s not the optimal air pressure – this number can be found in the manual. The maximum load number is the final piece of information you’ll find. It looks like this – 1500 LBS, for example. As you’ve probably guessed already, the number refers to the tire’s load carrying capacity in pounds (which makes it different from the load index).
A Few Tips for Increasing the Lifespan of Your Tires
Choosing the right tire size and opting for a tire that has the best possible treadwear, traction and temperature ratings will help you get the longest period out of the piece. Investing in quality tires will always make more sense because these tend to remain in good condition for a longer period of time and they ensure your safety on the road.
Apart from picking the right tire, you can do several other things to increase its longevity.
Taking proper care of the wheels can have a serious impact on the lifespan of the tires. Thus, you should consider regular wheel alignment and wheel balancing.
Wheel alignment and balancing will make the vehicle more stable on the road. When the wheels aren’t aligned, they’ll be subjected to different types of forces. As a result, the tires will get worn out unevenly and their lifespan will be decreased significantly.
Apart from guaranteeing the stability and the longevity of the tires, these procedures also boost the vehicle’s safety on the road. This is the main reason why opting for professional alignment will deliver a vast range of benefits. To get the best results, have your wheels aligned and balanced every two to three years. You’ll also need alignment if you’re experiencing problems like an off-center steering wheel, a vehicle pulling to one side, unstable vehicle or steering wheel vibrations.
If you don’t know how to choose the right tires or how to keep them in a good condition, you may want to refer to your user manual or talk to one of our experienced team of mechanics at Gator Custom Auto & Performance, mechanics you can trust. Choosing the right tires is of the uttermost importance and getting yourself informed is far from a challenging task. Dedicating a bit of time to doing research can save you money in the long run and guarantee the safety and comfort of your rides.
