Tire Size Guide: How To Read Tire Sizes?

To know how to read tire sizes is very important when purchasing new tires for the vehicle, so our tire size guide will be really useful for those, who are freshmen in this area.

For many people reading sizes is like reading Chinese, because they do not know basic information.

The thing is that each tire number and letter correspond with particular information for the vehicle. Such marks are standard within different manufacturers.

The sizing is standardized to aid mechanics and customers in installing correct tires. Some cars have systems that are computerized, which measure speed data, which is affected by the size of the tire.

Vehicle Codes

The sidewall stamping provides tire speed rating information, its purpose and loading capacity. A code lists a series of numbers and letter that explain tire specifications and dimensions.

  • R means Radial construction. The tire thread gives it added strength. It is usually found between the rim size number and aspect ratio number.
  • D stands for bias-ply tire construction. It is designed for providing a smoother ride on rough terrain, but the trade off is weaker treads and weaker plies. It is found between rim size number and aspect ratio number.
  • B means for belted tire construction. The thread gives bet traction and a smooth ride.
  • P means for passenger. Such tires are made for passenger vehicles, and the mark is found between the numbers.
  • M+S is Mud and Snow. That means the tire rides on snow and mud in the city without any troubles. As a rule, it is found before the numbers.

Tire Size Useful Guide On Reading The Numbers

Reading the numbers that are given as a slash, one should be rather careful as they define the tire’s width, rim size, and aspect ratio. For instance, you can see numbers like 185/65. Each of them has to do with the size.

The number before the slash (in this case 185) means the tire’s width . It’s the width that touches the road from one sidewall to another. The size is given in millimeters.

Aspect ration gives the high of tire’s the sidewall as a percentage, when compared to the tire’s width. We have the number 65, so that shows that the aspect ratio is 65%. In this very case the sidewall height is 65% of 185.

One more thing to pay attention to is the rim size. It’s the last number in the sequence found after letters; it comes after the aspect ratio. That’s the car’s rim size you should place the tires on. It is rather important to match both the tires and the rim size of the car.

While reading you tire size remember of the numbers structure: Rim/Section Width/Profile/Outer Diameter.

Tire Ratings

Last two tire code’s designations refer to speed and load ratings. They indicate tire’s maximum endurance in normal conditions. Load rating shows how much weigh the tires will handle horizontally and vertically.

Speed rating shows the highest speed the tires can travel. Our tire size guide will become clearer, if we show the examples of tires marks reading.

  • 3.00-4, 3.50-6, 4.00-8, 5.20-10, 6.00-12…: 3.00 tell the width section and the tire sidewall height in inches. Number 4 stands for the rim diameter (rim size) in inches. 3.00-4 tires fit a 4” diameter rim.
  • 4.10/3.50-4, 4.10/3.50-6, 5.30/4.50-6 : there are four parts of the marking. 4.10 is the tires section width . 3.50 stand for the tires sidewall height. 4 is the rim size (rim diameter). So, 4.10/3.50-4 tires are 4.1” wide, 3.5” tall on the sidewall and fit 4” rim.

Our tire size guide will be rather useful for drivers, who feel difficulty, when buying new tires and reading their sizes. One more thing to remember that such markers are also listed on the door-end of the vehicle.

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