You're going to be looking at plenty of specifications if you're buying new tires for your car. Choosing the correct size tire is critical if you want rubber that fits your wheels and performs well under your typical driving conditions. However, tire size isn't the only factor you should look at when browsing your local tire dealer's selection.
All tires come with three uniform tire quality grading (UTQG) specifications. These grades follow standards set by the US Department of Transportation, and they can provide you with some additional information about your tires. Understanding how to read these three grades will help you make a more informed tire purchasing decision.
Traction: Pulling G's
You've probably heard of "g-force" before, but this term typically shows up when talking about airplanes and pilots. Put simply, a "g" is a unit of measurement that refers to gravity experienced by an object relative to the gravitational pull of the Earth. When you stand on the surface of the Earth, you experience roughly 1g pulling you down to the ground.
Traction ratings use lateral gs to indicate where a car begins to lose grip. For example, a tire with a traction rating of 0.4g would begin to slide when 40% of its total weight is pushing laterally against the tires. UTQG traction grades go from AA down to C, with a better grade indicating a higher g-force limit before the tire begins to slide.
Treadwear: Living a Long Life
Treadwear ratings are, unsurprisingly, a measure of how well a tire holds up over time. Unfortunately, these ratings don't have the same scientific backing as traction ratings. As a result, treadwear ratings can vary somewhat between manufacturers. Also, unlike traction ratings, treadwear grades are numerical instead of letters.
A higher treadwear rating indicates that a tire will wear more slowly and last for longer. When comparing ratings, it's usually a good idea to only compare tires from the same manufacturer, as each company may use a slightly different testing methodology. High-performance tires also typically have a much lower treadwear rating, and some may have a rating of zero.
Temperature: Feeling the Heat
Finally, the temperature grade is effectively a proxy for a tire's speed rating. Temperature ratings go from A down to C, with higher ratings indicating that a tire can withstand hotter sustained temperatures. These temperatures correlate directly with speed, so a tire with an "A" grade can sustain higher speeds than one with a "C" grade.
Since most tires in the US meet the standards necessary to reach "A" temperature grades, it's usually better to look at the speed rating. This value will give you a better idea of how well your tire will stand up to prolonged use at high speeds.
Talk to a tire dealer to learn what tire would be best for your car.