Let's say that your tire number reads P225/70-R15, 89H.
- The first letter is a P for Passenger Tire; another option is LT for Light Truck.
- The 225 refers to the tire's width in millimeters.
- The 70 is a reference to the height (distance from rim to tread) as a percentage of the thread width (known as aspect ratio).
- R refers to the tire's construction - Radial, as opposed to B for Belted Bias or D for Diagonal Bias.
- The 15 refers to the size of the wheel in inches.
- Finally, the 89H represents the weight capacity of the tire, although this figure is not common.
Sometimes a speed rating is included in front of the tire construction (R/B/D) to indicate if the tire has been rated for very high speeds. This letter would be in front of the R. The fact that there is none on this tire number means the manufacturer does not recommend using this tire above 100 mph. There are several speed ratings for tires.
- S = 112 mph
- T = 118 mph
- U = 124 mph
- H = 130 mph
- V = 149 mph
- Z = rated for speeds in excess of 149 mph.
The V and Z rated tires have excellent dry pavement grip or traction but due to their soft rubber compounds, do not have a long life.
A tread rating indicates how long a tire should last. This figure is written in small letters on the sidewall of your tire. The higher the number, the longer the tire should last — 100 is the basic tread wear rating.
The traction rating works just like grading — ‘A’ being the best, ‘B’ is good, and ‘C’ is acceptable. This number is also found on the sidewall.
Temperature ratings work the same — ‘A’ best, ‘B’ good, ‘C’ acceptable. If you drive your car very hard, you want a temperature rating of ‘A’ because a ‘C’ would fail faster under these conditions. Again, look for this number on the sidewall.