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How to Read Tire Size

Are you at the point where your vehicle is due for a tire replacement? Picking the right tire size is crucial for fit and performance. If you’re not sure how to tell tire sizes, the team at the Fletcher Jones Motorcars tire center can help. We can help you learn how to read tire sizes, and then our team in Newport Beach can help fit your vehicle with Mercedes-Benz Original Tires

What Do Tire Sizes Mean?

RepairThe sidewall of your tires will be marked by a series of letters and numbers. These markings indicate things like the size and construction of your tire. Fletcher Jones Motorcars covers the most common tire markings below: 

Tire Type

Tire classes are the first mark and indicate the type of vehicle the tire is made for. Euro metric tires are the exception as they don’t come with a letter. However, passenger vehicles are indicated by the letter “P,” and light trucks are indicated by the letters “LT.”

Tire Width

A three-digit number is next in line and is used to represent the tire width. This measurement is taken in millimeters from one of your tire’s sidewalls to the other. So, if you have a passenger vehicle with a tire width of 245 millimeters, the marker will look like, “P245/.” 

Aspect Ratio

The height of the tire’s cross-section to its width is called the aspect ratio. This measurement, which is a two-digit number, will be found after the tire width and slash mark. 


Tires can be constructed differently, but the most common tire type is a radial tire. Radial tires are noted by the letter “R” and are built with layers of fabric with cords that run at right angles to the circumference of the tire. These tires offer increased performance and durability. 

Wheel Diameter

The measurement in inches of the wheel the tire will fit is called the wheel diameter. For example, the number “17” means your tire will fit a 17-inch wheel. 

Load Index

The maximum load a tire can carry while properly inflated follows the wheel diameter and is called the load index. Vehicle manufacturers set specifications that you need to meet or exceed when choosing your next tire. 

Speed Rating

Next is the speed rating. Tires can range in their speed ratings, and these ratings are represented by a letter. Starting with the low “Q” rating, tires are able to have a top speed of 99 mph. Topping off the tire range, “(Y)” tires are built for a speed of 186 mph and up. It’s important to keep in mind that the speeds your tires are capable of are not the same as the speed at which you should actually travel. Posted speed limits, weather, and road conditions all need to be accounted for. 

Other Tire Codes & Marks

While the above are the top indicators of tire size, there are still more tire markings to decipher. On the sidewall, you may also see the following tire markings: 

DOT Symbol

“DOT” is a mark placed by the Department of Transportation to show that the tire has passed all the minimum DOT standards to be sold in the U.S. This required symbol is followed by another letter and number. These denote where the tire was manufactured. Following that, there are two more letters that indicate the size. 

Tire Identification Number

This code is an optional code and is placed by the tire’s manufacturer to indicate tire tread, construction, and the week and year the tire was created. 


Uniform Tire Quality Grading, otherwise known as UTQG, is a system developed by the U.S. Department of Transportation. This system grades tires based on tread wear, traction, and temperature resistance. System ratings run from A to C for traction and AA to C for temperature. C is considered the lowest rating on the scale. 

Maximum Tire Pressure & Load

Maximum tire pressure is marked by a number followed by the letters “PSI.” This indicates the maximum tire pressure a tire can hold and safely operate with. A number followed by the letters “LBS” is the maximum load. The maximum load is the amount in pounds that a tire can carry when the tires are at maximum inflation. These numbers are truly maximums, not the ideal numbers for vehicle operation. Check your owner’s manual for ideal specs. 

What Size Tires Do I Need For My Mercedes-Benz?

You now know how to read tire sizes, but you still need to pick the right tire to fit your vehicle. Your owner’s manual is a great place to start, or the techs at the Fletcher Jones Motorcars tire center can help. We stock Mercedes-Benz Original Tires designed to fit the size and performance of your Mercedes-Benz.  

Contact Us for Mercedes-Benz Tire Tips Near Orange County!

Whether you’re in need of repairs or are looking for tire maintenance tips, you can find the help you need at Fletcher Jones Motorcars. Contact us today to learn more about picking the right Mercedes-Benz Original Tires or how to care for the tires you have near Costa Mesa!

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