- P = Passenger Tire (LT = Light Truck)
- 235 = Overall width of the tire in millimeters
- 75 = Sidewall height (distance from rim to tread) as a percentage of the thread width (known as aspect ratio)
- R = Tire construction, this one is Radial (also, B = Belted Bias, D = Diagonal Bias
- 15 = Represents the size of the wheel in inches
- In this example, the tire has the number 89H. This is the weight capacity of the tire. However, in most cases, you will not see this heading on the sidewall.
- A speed rating is sometimes put in front of the R (or B or D). A straight R rating means that it is rated for speeds of up to 100mph. The manufacturer does not recommended this tire for speeds greater than 100 mph. Other speed ratings are: S=112mph, T=118mph, U=124mph, H=130mph, V=149mph, & a Z rated tire is for speeds in excess of 149mph.
- The V and Z rated tires have excellent dry pavement grip/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.
Tire Inflation and GAWR Information:
The vehicle’s tire information placard (certification label) includes information regarding the tire size, inflation, GAWR and other information. The tire information placard is usually located on the driver’s door hinge pillar, door latch post, or the door edge. In RVs the tire information placard is placed on the bulkhead at the left of the driver’s seating position.
Example – Tire Information Placard (Certification label):
Under no circumstances should the tire inflation pressure be reduced below that stated on the vehicle’s tire information (certification) placard to achieve improvements in ride comfort. If you do not know where the tire information placard is, contact your vehicle manufacturer for its location and tire inflation recommendation. For RVs, the certification label is usually placed on the wall or bulkhead to the left of the driver’s position.
Check Cold Tire Inflation Pressure Prior to Driving:
The cold tire inflation pressures of each wheel should be checked at least once a month and any corrections in cold tire inflation pressure should be made prior to a trip. “Cold” means that the tires are at the same temperature as the surrounding air, such as when the vehicle has been parked overnight. Never bleed air from a tire that has been run. It is normal for a tire’s inflation pressure to increase (hot inflation pressure) after running (for example 30 minutes or more driving time).