Tires have codes and symbols molded into the sidewalls. What do they all mean? And should you care?
Let’s answer the last question first: Yes, you should care about the codes embossed onto your tires. They convey important information that, if you ignore it, can have catastrophic consequences. The codes tell you that you’re buying a tire that is the right size, can support the right load, and can handle the heat and stresses of certain speeds.
Interpreting Tire Codes
Let’s break down the following code:
- 195. This is the tire’s tread width in millimeters.
- 55. This is the aspect ratio—the height between the bead and the top edge of the tread as a percentage of tire width. The 55 means the height is 55 percent of 195 mm, or about 107 mm.
- R. That’s short for radial.
- 15. This is the diameter in inches of the proper wheel. Never deviate.
- 85. This represents the weight the tire can support. The higher the number, the more weight the tire can support.
- V. This is the speed rating. V means the tire is built to withstand the stresses of speeds up to 149 mph. Other common speed ratings: Q (up to 100 mph, truck tires); R (up to 106 mph, truck tires); S (112 mph); T (118); H (130); Z (over 149); W (168); (W) (over 168); Y (186); and (Y) (over 186)
Other Alpha-Numeric Codes
P. - P is for Passenger tires (not always present).
C. - C is for Commercial tires (not always present).
LT. - Light Truck tires are intended for pickups, vans, and heavy SUVs. They typically have a higher Load Range (see below).
M+S or M&S stands for Mud and Snow. It means the tread is designed with a certain percentage of openings that promote traction in light mud and light snow. These are all season tires. The words All Season may appear on the sidewall instead. They can handle light mud and light snow; they are not as effective either as a mud tire or a winter tread.
Outside, SFO (Side Faces Out) or similar messages appear on some tires with asymmetrical tread. These tires have a different-shaped tread on the outer ribs than on the inner ribs. For the tire to deliver traction properly, certain parts of the tread must be either toward the outside or inside. Usually, these tires can be rotated side to side as well as front to back. Some tires may be coded SFI (side faces in).
The tiny type that is typically near the bead, where the tire adheres to the wheel, indicates Maximum Pressure and Load Range.
- Maximum Pressure. This is the highest pressure you can use to inflate the tire safely. Typical is 36 psi (pounds per square inch). Tires that can handle higher pressures often engender better fuel mileage.
- Load Range. Most passenger tires are Load Range B, which is the measured equivalent of the strength derived from a 4-ply rating. XL means extra load, indicating that the tire can be inflated to higher pressure, usually on high-performance tires. Some truck tires have a load range letter deeper into the alphabet, reflecting a stronger tire that’s good for heavy loads; for towing; or for traveling off road: Load Range C (6 ply), D (8 ply), E (10 ply) and F (12 ply).
- Tire Wear. A 3-digit number, it guides a buyer on miles to expect. The higher the number, the longer the expected tread life. A tire with a 760 or 620 treadwear grade will last longer than a tire coded 300.
- Traction. The deeper into the alphabet, the worse the traction performance—the ability of a tire to generate straight-line traction on dry pavement. AA is best, followed by A, B and C.
The Department of Transportation requires all tires to be used in the United States to carry the DOT code. The first four letters/numerals are a code for where the tire was manufactured. The final four numerals show the week (48, for example) and year (15 would be 2015). If the last four digits are 4815, the tire was built in the 48th week of 2015. PTO tells you in every tire listing the year a tire was made.
- Mountain snowflake. This indicates a winter tire. It is designed for deep snow, with an aggressive tread design and probably a higher silica content in the tread compound to keep the tire more flexible in cold weather. Winter tires should be removed before warm weather; failure to do so will lead to premature wear.
- Arrow. If the tire is engineered to roll in one direction, the arrow shows that direction. Directional tires can be rotated on the same side only, front to back and back to front.