You’ll probably see a lot of numbers and letters on your tire’s sidewall. At first glance, it might seem like this is just an embedded barcode or identifier that helps with tire manufacturers’ quality control. So what do the numbers on tires mean? Here we explain the meaning of these numbers. Let’s start with the letter closest to the left.
P, LT = Tire Type
It is possible that your tires will start with either a “P”, or the letters “LT”. This is an indication of type. The “P” symbol denotes a P-metric (or American tire) which means the tire meets the requirements of the United States. The “P” indicates that the tire is intended for passenger vehicles such as sedans or SUVs. The “LT” sign means that the tire is intended for light-duty vehicles. The “LT” is usually located at the tire’s beginning, but it can also be found at the tire’s end. The “ST” may be found on the tire. This stands for “special trailer”. If the tire has no letter(s) at its beginning, it is likely that it’s a Euro metric tire.
The tire width measurement is next to the letters that are used to start things off (or lack thereof, in the case Euro-metric tires). This number is always the first three-digit number and indicates how many millimeters the tire measures from one sidewall to the other. If your tire says “P205”, then it is a P-metric tire that is intended for passenger cars with a tire width of 205 millimeters.
The Next Two-Digit Number = Aspect Ratio
The tire width to cross-section ratio is the height at which the aspect ratio is equal. The aspect ratio can be checked by looking at the first two-digit number located on the sidewall. This number is after the tire type, and the three-digit width measurement. If a tire has a reading of “P205/70R”, the aspect ratio will be 70. This means that the tire’s height is 70% of its width.
Types of Construction
If the numbers on the tires sidewall says “P205/70 R.” This “R” denotes the tire construction. It stands for “radial.” This is the industry standard for most tires today. However, you might see a “D”, for diagonal plies, or “F” to indicate run-flat tires.
Second Two-Digit Number = Wheel Diameter
The second two-digit number found with the construction type is used for defining wheel diameter. The wheel diameter simply refers to the distance between the two ends of the wheel. For example, “R 15” means that the tire’s diameter is 15 inches.
Load Index = Third Two- or Sometimes Three – Digit Number
The load index is the third number, usually two or three digits, that you will find on the tire sidewall. This is the weight limit that the tire can support. You will need to consult a chart to find out how to determine this weight limit. Tires with a load index 65 can support 639 lbs. A tire with a load index 100 can carry 1,764 pounds. The load index numbers can range from 65 to 150.
Speed Rating = Last Digit
The last numbers on tires is a speed rating indicator. It’s the speed rating indicator, which is simply the recommended top speed for safe travel over sustained periods. The speed ratings of passenger car tires can vary but are usually either H (130 miles an hour) or V (135 miles per hour). Speed ratings can also be represented by symbols (A1-8 and 3 mph-25 mph, respectively), though they are rare. A “Y” is the highest speed rating, which means that a tire can travel more than 186 mph. Hypothetically, suppose we have a tire sidewall reading like this: P205/65 R15 80 H. Let’s now look at what each letter and number mean.
- P: P-metric for passenger vehicle tire
- 205: Tire width in millimeters
- 65: tire aspect ratio
- R: Radial construction type
- 15: Wheel diameter in inches
- 80: Load index. A tire that can carry 992 pounds.
- H is the speed rating. It indicates a tire capable of traveling at 130 mph sustained top speed.
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