How to Read a Tire Sidewall: Size, Load, Speed and DOT Code

The size and service description

NHTSA's tire safety brochure uses P215/65R15 95H as its example:

Use our size calculator to turn the size into inches, and the load and speed decoder for the last two characters. For this example, 95 is 690 kg (1,521 lb) per tire and H is 210 km/h (130 mph).

The DOT Tire Identification Number

Tires sold in the United States carry "DOT" followed by a Tire Identification Number (TIN). It identifies the manufacturing plant, a size code, an optional manufacturer code, and the date of manufacture.

The date is the last four digits: two for the week and two for the year. NHTSA's example: 0308 means the tire was made in the third week of 2008. The full TIN may appear on only one side, so check both. More in our tire age guide.

UTQG grades

Most passenger car tires sold in the U.S. carry Uniform Tire Quality Grading marks, set by the U.S. government:

• Treadwear: a number comparing the tire's wear rate to a control tire graded 100. A 200 should wear about twice as long as the control tire in the test. NHTSA reports that most current tires fall between 201 and 500.
• Traction: AA, A, B or C, from best to worst, measuring stopping ability on wet pavement in a straight line.
• Temperature: A, B or C, measuring resistance to heat build-up at speed. NHTSA notes that sustained high temperature can cause a tire to deteriorate.

UTQG grades are useful for comparing tires from different makers, but treadwear tests are run under set conditions, and actual mileage varies.

Maximum pressure and load

Somewhere on the sidewall, in small print, you will find the maximum load and maximum inflation pressure. NHTSA stresses that the correct pressure for your vehicle is the one the vehicle manufacturer lists, not the maximum on the tire. Use the sidewall maximum only as a limit never to exceed.

Other markings

• Tread and sidewall plies: the materials and number of layers under the tread and in the sidewall.
• M+S or M/S: mud and snow, common on all-season tires.
• Mountain-snowflake symbol: a three-peak mountain with a snowflake, found on tires that meet a severe snow traction test.
• Load range letter (LT tires): such as C, D or E, indicating construction and maximum pressure.
• Tubeless: nearly all modern car tires are tubeless.
• Treadwear indicators: small arrows or "TWI" marks show where the raised wear bars sit in the grooves. When the tread is level with them, NHTSA says it is time to replace the tire.

Putting it together

When you buy tires, confirm four things against your vehicle's door label or owner's manual: the size, a load index at least as high as the original, a speed rating at least as high as the original, and the date code (newer is better). Our plus sizing guide covers changing sizes, and the tread and pressure guide covers care once they are on.

Common questions

Where is the tire size on the sidewall?

In large characters, usually starting with a letter or the width, such as P225/65R17 or 225/65R17, followed by the load index and speed rating.

Is the pressure on the tire the one I should use?

No. NHTSA says the correct pressure is what the vehicle manufacturer lists on the Tire and Loading Information label or in the owner's manual. The figure on the sidewall is the tire's maximum.

Why can't I find the DOT date code?

The full Tire Identification Number may be on only one side. NHTSA advises looking on both sides of the tire.

What is a good treadwear grade?

Higher numbers should wear longer relative to the control tire graded 100, so 400 should last about twice as long as 200 in the government test. Real mileage depends on driving, roads and maintenance.