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What Tire Size Do I Need?

Learn how to find your tire size with help from Blain’s Farm & Fleet.

When you’re looking for new tires, the most important thing to know is your tire size. There are a few places you can look to find the tire size that is compatible with your vehicle. You can look for your tire size:

  1. In your vehicle’s owner’s manual.
  2. On a sticker that’s often located inside the driver-side door jamb, glove compartment, or fuel door.
  3. If you see multiple sizes listed, it’s best to look on the tire itself (see below).

Reading the sidewall markings on your tires to get the tire size:

Finding Your Tire Size

Treadwear – The treadwear rating measures the tire’s durability. It does not measure the projected tread life. Tread life can be affected by driving habits, driving surfaces and other factors. Individual tire manufacturers determine the treadwear rating. The ratings can vary between tire brands, so when you’re comparing tires, it’s important to compare ratings within the same brand. The higher the treadwear rating, the longer the tire tread will last. In our example, the 440 treadwear rating indicates the tread would last twice as long as a tire with a rating of 220.

Traction – The tire’s traction rating measures the tire’s ability to stop on a wet, straight surface in controlled conditions. The traction rating doesn’t include the tire’s traction on ice or snow. It also doesn’t include the tire’s cornering ability. Traction can be graded by AA, A, B, or C, with AA being the highest traction grade.

Temperature – Temperature rating measures the tire’s resistance to generated heat at the recommended tire pressure, in normal driving conditions. Temperature grade ranges from A to C. “A” is the highest rating a tire can have, making it the most resistant to generated heat.

Tire Class – The first character on the sidewall markings is the tire’s class. “P” means that the tire is a passenger car tire. “LT” means the tire is a light truck tire. “ST” means special trailer. If there is no letter before the tire size, it means the tire is a European metric tire.

Width – The next section of the tire size is the width. The tire’s width is measured in millimeters.

Ratio – The ratio number is the height of the sidewall from the wheel to the top of the tire tread. The height is a percentage of the width. In our example, the ratio is 55 percent of the 205 mm width, equaling 112.75. A lower aspect ratio equals less sidewall, meaning the tire moves less on turns.

Rim Size – Rim size is the next character on the sidewall markings. The size of the tire’s rim is measured in inches. Our example shows a 16 inch diameter. That means you need to pair it with 16 inch rims.

Load Index – The next figure on your sidewall is the load index. The tire’s load index measures the maximum amount your tires can safely carry. Your tire’s load index will range from 0 to 279. Each index rating represents a different weight, measured in pounds. In our example, the tire has a load index of 89. A load index of 89 indicates that 1,279 pounds is the maximum amount the car can carry safely. Maintaining the correct load index is very important for your tires.

Load range identifies the load and inflation limits of a tire. Tire load ranges are indicated by letters B, C, D, E or F. The load pressure is measured in PSI.

B = 35 PSI
C = 50 PSI
D = 65 PSI
E = 80 PSI
F = 95 PSI

Speed Rating – Speed rating is determined by the U.S. Government. Tires are tested to see if they meet the minimum standards for reaching and keeping a specific speed. Different letters designate specific speed ratings for each tire.

Q = 99 mph
S = 112 mph
T = 118 mph
U = 124 mph
H = 130 mph
V = up to 149 mph
Z = 149 mph and above
W = 168 mph
Y = 186 mph

Once you know your tire size, you can use our tire lookup feature to find tires online. You can also find quality tires for sale at your local Blain’s Farm & Fleet tire shop. Ask one of our friendly associates about tires for sale and even discount tires. At Blain’s Farm & Fleet, you don’t have to settle for cheap tires. We offer quality brands you trust, such as Goodyear, Michelin and Cooper Tire. We also offer a variety of tire services including tire balancing and tire repair. You can call 1-800-365-9936 to schedule an appointment or request a quote online.


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