Different Tire Sizes With Pictures

November 23, 2021

How to Read Your Vehicle's Tire Size

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Your vehicle's performance and safety depend on buying the right tires for your vehicle. Choosing the best model for performance is half the game. You must buy the tires that fit your vehicle. To know what tires fit your car or truck, you must learn how to read your vehicle's tire size. You may think that you need a tire to rim size calculator but that's not true. Reading your vehicle size is a lot easier than you may think. Here is your step-by-step guide to reading your vehicle's tire size today.

Locate Your Vehicle's Tire Size

The first step is finding the recommended manufacturer tire size for your vehicle. This 10-digit sequence is a combination of numbers and letters. The easiest way to find it is by looking in the owner's manual. But, don't worry if you lost it or can't find it. You can find the tire size in one of the following places:

Inside your vehicle's glove box door
Driver's side door jam
Gas tank hatch

If your vehicle has more than one door, you should check the side door jam for all drivers' side doors.

Write Down Your Tire Size and Divide It into Sections

An example of a vehicle tire size is P225/70R16 91S. It's recommended that you split the sequence into three sections to read it easily. The example above can be split into the following sections:

P225
70R16
91S

Learn the Tire Type and Width of Your Vehicle's Tire

The first section of the tire size sequence is the type and width of your vehicle's tire. All tires are type P, LT, T, or ST. The P stands for passenger vehicles. P tires can fit cars, minivans, SUVs, and some light duty trucks. If your tire size has LT instead, it's a light truck type of tire. It fits vehicles that can handle heavier duty such as pulling trailers or carrying heavy cargo. Also, there are special designations for spares and special trailer tires. If the tire label has a T, it means it's the vehicle's spare. In contrast, tires for a special trailer have an ST prefix.

The numbers after the letters are your tire width in millimeters. The width is the measurement from one sidewall to the other. Our example is a tire for a passenger vehicle with a width of 225 millimeters.

Figure out the Aspect Ratio, Construction, and RIM Diameter

In the section after the slash, you will find the aspect ratio, construction, and RIM diameter. The aspect ratio refers to the wheel rim offset.

The tire aspect ratio is a percentage calculated by dividing the tire height off the rim by the tire width. You may calculate this number by using a wheel offset calculator but it's a lot more complicated than reading your tire size. If your tires have a ratio of less than 60, they may provide better vehicle handling performance.

There are two types of tire construction. Tires are radial, diagonal or bias ply. The construction refers to the orientation of the tire's internal ply cords. R stands for tire ply cords being oriented in a radial direction, perpendicular to the axis of rotation.

After the construction, you will find the RIM diameter for your tire. The example mentioned in step two is a tire with 70 percent aspect ratio of radial construction that fits a 16-inch rim.

Learn the Load Index and Speed Rating of Your Vehicle's Tire

In the section after the space, you will read the load index and speed rating of your vehicle tire. The load index is the number that indicates how much weight your tire can support. The number is an index so you can't figure out the exact weight by only using the number. You must search the number on your size in the load index to learn the exact weight. A tire load index can range from one to 150.

The letter after your load index is your speed rating. This number tells you the speed capability of your tire based on certain tests. If your tire speed rating is S, your tire can handle speeds up to 112 miles per hour. In contrast, tires rated R can only handle speeds up to 106 miles per hour.

In our example, the tire has a load index of 91 and an S speed rating. The tire may be able to support 1,356 pounds and handle up to 112 miles per hour.

Reading your vehicle's tire size is easier than using a rim and tire size calculator. You must break your 10-digit sequence into several parts to make sure you understand the measurements better. Keep in mind that your vehicle may have more than one tire size depending on the vehicle and tire use.

Guerin Whilich