A Complete Guide on How to Read Tire Types & Sizes
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When the subject of vehicle performance comes up, typical topics include engine horsepower, transmission type, suspension layout, and the braking system.
Each of those elements plays a significant role in how a car accelerates, handles, and stops.
But what about where a vehicle actually comes into contact with the road?
Tires play a vital role in car performance, with different categories designed for specific conditions like ultimate road traction, grip in ice and snow, all-around driving, and off-road adventures.
Have you ever looked at a tire sidewall and wondered what all of the numbers and letters mean? Each character tells an important story about the tire's design and intended use and helps you select the one that meets your needs.
What do the numbers on a tire mean? Let's look at the different types of tires available and how to read tire size.
The different categories of tires
Just like there are different types of shoes for running, hiking, or simply walking around town, there are many sorts of tires for varying road conditions.
Touring tires, or all-season tires, offer a balanced package that works well in various circumstances like rain or snow, along with pleasing ride quality and excellent treadwear. Touring tires are a wise decision for the driver who encounters a little bit of everything and doesn't need maximum performance.
Performance tires, or summer tires, are for drivers looking for maximum grip and handling in ideal warm weather conditions. With a rubber compound designed to stick to warm roads and hug the corners, performance tires are all about the thrill of driving. However, in cold weather or ice and snow, performance tires can be hazardous, so it's best to confine their use to warmer times of the year. Due to their sticky rubber compound, summer tires tend to wear out faster than all-seasons.
Snow and ice tires, or winter tires, feature rubber compounds and tread designs for adhering to the road in frigid, slippery conditions. Snow tires use a softer form of rubber that remains pliable no matter the temperature, along with enhanced grooves and "siping" carved into their tread. While you can use winter tires year-round, you may experience sloppier handling and increased stopping distances. A good rule of thumb for winter tire tread wear is they're suitable for four seasons of regular use, though some may last longer than that.
Off-road tires, or all-terrain tires, are for the drivers of SUVs and trucks looking to explore off of the beaten path. With deeply grooved treads and thick sidewalls, off-road tires dig into dirt and mud, helping your vehicle tackle the most challenging conditions. However, off-road tires aren't the best for on-road handling, accelerating, and stopping with tall sidewalls and thick treads. And with their chunky blocks of soft rubber tread, they may wear out quicker than the average tire.
Although some are road-legal, competition tires are for race tracks or other specialized events like autocross. Often using a flat surface using no tread, competition tires vary in composition to enhance grip during high-performance driving. With their slick surface resembling that found on a race car, competition tires are a serious piece of driving equipment. Due to their focused intention, competition tires tend to wear out quickly.
One great way to save on wear-and-tear items like tires is opting to buy a used car instead of a new one because buying used can save you thousands. But where can you go for not only a great price but also a quality vehicle? Shift's certified mechanics perform extensive 150-point inspections on every car and have complete vehicle history reports, so you know your used car feels as good as new.
What do the numbers on a tire mean?
Although the sequence of numbers and letters printed on your tire sidewall might be confusing, you can easily decode them with the correct information.
The first character in the series is typically a P, indicating the tire's designation as a P-Metric tire, designed for passenger vehicles in the United States. If there's no letter at the beginning of the sequence, you may have a Euro-metric tire with different load capacities than a P-Metric tire.
If the string of numbers and letters begins or ends with an L.T., the tire's intended use is for a light truck or sport utility vehicle. Typically, light truck tires require higher tire pressures than those for regular passenger vehicles.
Your owner's manual or tire placard in your doorjamb can guide you on which type of tire your car needs.
Next in the series is a three-digit number noting the tire's width. The characters on the side of a tire may begin with P245, noting a passenger tire that's 245 millimeters wide.
The following number shows the ratio between the height of the tire's cross-section and its width, also known as the aspect ratio. For example, a tire with the notation P245/50 denotes its cross-section height is 50 percent of its width. Larger aspect ratios correspond to thicker sidewalls, typically found on off-road tires.
Usually following the aspect ratio is the letter R, demonstrating the tire features radial construction, in which layers span radially from side to side.
After the construction designation comes the wheel diameter. A tire with a character sequence reading 245/50R19 is 245 millimeters wide, with a 50 percent aspect ratio, riding on wheels with a 19-inch rim diameter.
Next is the load index and tire speed rating, signified by two numbers and a letter. The load index demonstrates the maximum weight the tire can support, with higher numbers corresponding to heavier figures. And the speed rating lets you know how fast you can drive on a particular tire, with different letters indicating varying maximum speeds.
For instance, a tire load index of 98 can support a maximum load of 1653 pounds, and a top speed rating of V is good for up to 149 miles per hour.
A DOT symbol on the side of the tire shows that it conforms with the rules established by the Federal Motor Vehicle Safety Standards in the U.S.
Following the DOT notation, the tire identification number, or TIN, is a sequence of up to 12 characters showing its manufacturing date and location.
Last but not least is the UTQG grade, or Uniform Tire Quality Grading, which approximates a tire's useful treadwear, traction, and temperature traits.
Treadwear ratings are typically indicated by three digits, with higher values corresponding to greater mileage values. The range of grades for tire traction is A.A., A, B, and C, with the first being the best. And the temperature grades are A, B, and C, with A noting the most robust tire.
Tire size is just one of the many details to consider when car shopping. Although buying a new-to-you vehicle can be fun, sometimes it's a hassle. Who likes to negotiate with a salesperson, and how can you know you're getting a good deal? Shift takes the stress out of buying your next vehicle with their no-pressure sales environment. At Shift, you'll get a fair, no-haggle price driven by powerful machine-learning algorithms and tons of data.
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April 15, 2022
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