Knowing how to read a tire can give you important information about the type of tire on your car, motorhome, trailer, or motorcycle. This can also be useful when buying parts for your vehicle considering tire improvements or when changing your tires according to the season if you live in places where winter can be a problem. By knowing how to interpret the numbers and letters on a car tire, you can find out the speed level, the temperature resistance, the load index numbers, as well as the width and diameter of the tire.
Step 1. Read the name of the tires and the manufacturer
These are printed in large letters towards the outside of the tire. The brand of the company is included, such as Hankook, Michelin or Goodyear.
The tire name can be just letters or a combination of numbers and letters, such as Goodyear’s Eagle F1 GS-D3, Hankook Ventus R-S2 Z212, or Kumho Ecsta MX
Step 2. Look at the description of the service
The service description, although it does not appear on all tires, usually appears right after the manufacturer's name. It comes with either a "P", "LT", "ST" or "T".
- "P" means passenger car.
- "LT" stands for light truck.
- "ST" means special trailer.
- "T" stands for temporary and worn as a spare tire.
- "BP" means aesthetically marked by the passenger.
Step 3. Find the aspect ratio and width
This is a series of numbers that are right after the service description. The series of numbers and letters will have a forward slash dividing them and will have the general form www / aaCrr.
- The first series of three numbers will tell you the tread width of the tire in millimeters. The tread width can vary from 155 to 315.
- The two numbers after the bar show the aspect ratio of the tire. This is the percentage of tread and width, which is equal to the height of the sidewall. The average ranges from 55 to 75 percent for most passenger vehicles.
Step 4. Know the internal construction of the tire
Most likely there is an "R", this mark is usually right after the aspect ratio. "R" stands for radial construction, an industry standard for passenger vehicles. Some trucks may have a "B", which stands for diagonal belted structure, however, it has largely been discontinued due to mishandling issues.
Step 5. Know the diameter of the tire
Typically, the tire size for which the tie-down was fitted appears immediately after internal construction. So for example, if it is 22 inches, you will have a tire whose rim diameter will also be 22 inches.
The letters in the SC or C position signify the speed level of the tire (pre-1991) or the construction of the tire. An "R" means the tire is of radial construction. If there is an "HR", this is a high speed radial tire
Step 6. Find the tire's load index
This number is very important as the load index is the amount of relative load that the tire size can carry. The higher the load index number, the higher the load capacity.
- The index is not a difficult number, it is just a class symbol. To find out how many kilos the tire can handle, refer to a tire load capacity chart.
- To find out how much your entire car can carry without putting undue pressure on its tires, multiply the number you found in the load capacity per tire by four. After all, you have four tires.
- Never replace tires with those that have a lower load index than the originals. You always want to have tires with the same or "higher" load index. So if you had tires with a load index of 92 to begin with, you will want to have tires with at least a 92 index or higher.
Step 7. Find the speed rating of the tire
The speed rating indicates that the tire can withstand a specific load at a certain speed. The most common speed ranges are S, T, U, H, V, Z, W, Y, and (Y).
- S means that the tire can travel at 112 mph for extended periods.
- T means the tire can travel 118 mph for extended periods.
- U means the tire can travel 124 mph for extended periods.
- H means the tire can travel 130 mph for extended periods.
- V means the tire can travel 149 mph for extended periods.
- Z means the tire can travel more than 149 mph for extended periods.
- W means the tire can travel 168 mph for extended periods.
- And it means that the tire can travel 186 mph for extended periods.
- (Y) means the tire can travel more than 186 mph for extended periods.
Step 8. Find the temperature-resistance index
This represents the tire's resistance to heat generated at high speeds on the inside of the tire. This can be an A, B, or C rating, with A being the highest strength and C being the lowest.
Step 9. Identify the Department of Transportation code by locating the numbers that follow the acronym DOT
Step 10. Find the numbers for the cold inflation near the inside edge of the tires
This tells you the pressure at which the tire should be in order to optimize its performance.