All About Tires: What Do The Numbers On a Tire Mean?

All About Tires: What Do The Numbers On a Tire Mean?

Tires are one of the most important pieces of what makes your car go, and yet they can sometimes be a little mysterious. Each tire has several numbers and symbols on it that have different meanings, and other important things that you should know about your tires.

If you need help understanding any of the tires sold on our website or need to talk to a tire expert, just contact us and we're always happy to help!

How To Find Your Tire Size

Every tire has three numbers that determine the specific tire size. It is extremely important to get this information correct, because before mounting tires on wheels, the tire and wheel diameters must always be confirmed to match.

You can find your tire size in your car owner's manual, or by looking at your tire sidewall where you'll see a series of numbers and letters that looks something like this: 205/65 R 15.

Tire Width

The first number you see, 205, is what's called the tire's width. This means that the tire width is 205 millimeters wide.

Aspect Ratio

The second number you see is the aspect ratio, and what this means is what the sidewall height (from wheel rim to top of the tread) of your tire will be as a percentage of the width. So in our example the height of the tire is 65% of the tire width.

Rim Size

The last two digit number is what's called the rim size or rim diameter. In our example, this tire requires a 15-inch diameter wheel to be put on your vehicle. Since we need our new tires to fit the wheel, the numbers for the rim diameter are critical when purchasing new tires!

In addition to these three numbers that are visible from outside of the tire, there are several other codes and markings that help you determine what type of performance features you have within your tires! We'll go over what each one means below:

The tire letter meaning refers to the tire's construction: R for radial, D for diagonal and RF which means run-flat. This means that the tire in our example has a radial construction.

This gives us an idea about what those numbers on tires mean and how to read your tire size! There are also other key elements you should know about your tires such as knowing when it's time to replace them or how to read their temperature rating which can affect fuel economy.

Once you know the tire's width, aspect ratio, and rim size you can then search for new tires by tire size, which is the only accurate way to replace tires.

How To Find Your Tire's Speed Rating

The tire speed rating, or maximum speed sustainable by the tires, is indicated by a letter which is located on the sidewalls of your tires. As you advance through the alphabet, each letter gets faster than the one before it. The exception is H which we'll explain that below.

The tire speed rating is what will keep your car in control while traveling at high speeds. Each letter represents the maximum speed for which these tires are rated to be driven at by the Department of Transportation, and what you'd like to know next is what that number means!

B - 50 mph (80 km/h)

C - 61 mph (98 km/h)

D - 68 mph (109 km/h)

E - 80 mph (129kmph ) If you're driving on a highway where the legal limit of speed is 70mph or above but less than 81mph, this would apply to you. These numbers represent how many kilometers per hour your vehicle can go over any given period of time so they may seem arbitrary

High performance racing tires are rated ZR and can reach speeds over 168MPH on some models when needed for high demand driving conditions or challenging roadways.

The tire load index and speed rating are what you should pay the most attention to, and what will be of greatest benefit to your vehicle.

How To Find Your Tire's Load Index

To find the load index of your tires you'll need to look your tire's sidewall. There you'll find three different numbers, which are also sometimes accompanied by a number and a letter combination.

The higher the tire load index number, the greater its carrying capacity for weight-bearing activities such as tow trailers; with load index values ranging from 0 (no capability) up through 150 which equals full lifting power!

The letter after this number provides information about what type of vehicle the tires are used for; H stands for passenger car use only but there are other letters like which stand for whether they are used in trailers, other passenger vehicles, light trucks, or other vehicles.

The carrying capacity for each value can be found on a load index chart.

How To Find Your Tire Tread Depth

Tire tread depth is one way we measure how much wear a tire has before they need replacing. Tires should be checked for tread depth every time you rotate your tires at the recommended mileage interval.

Here's a simple trick you can use: Place a penny head first into several tread grooves across the tire. If you always see George Washington's forehead, then your tires are in definite need of replacement and it may be time for an upgrade!

Other Tire Numbers and Symbols

In addition to things like the tire size and speed rating, there are other symbols and and letters that you may find on your tire's sidewall which you can use to learn other things about your tires.

Winter Tires

If you see the three-peak mountain snowflake symbol on your tire, this indicates that they are rated for severe winter weather conditions. The unique shape is identified by a single snowflake bordered outside with an outline of 3 peaks in zigzag form; it means these tires have met rigorous standards and can handle any type of winter storm!

Tire Comfort Index

You can also find what's called a tire comfort index (or TCI) on the sidewall. The number is used to rate how comfortable and quiet your tires will be, while you're driving on them. Not all tires have this rating, but tires with higher numbers are going to give you a more luxurious ride!

S-Mark Rating

The S-Mark is a symbol that the tire has met all sound approval requirements to be sold in compliance with European Union standards. All new tires produced since 2011 must have an S-Mark rating in the EU, but not all tires sold here on U.S soil carry it - so make sure you check before buying this pertains to you!

E-Mark Meaning

The E-mark, found on the sidewall of a tire designates that it meets minimum EU and international standards relating to size, load index/speed rating. This marking confirms testing has met adequate EU performance regulations for your safety.

How To Find The Year of Production

The last four digits of a tire's DOT serial number indicate what year the tire was manufactured. The first two letters represent what week, and then what day which is based on a standard calendar that starts with "A" being the first week starting Sunday - ending Saturday seven days later.

So for example: If your DOT code reads A0118 it means the tire was produced in January 18th of 2018. There can be no more than eight numbers to determine what year so if you have any other combination besides those shown above, simply add zeros as needed until there are only eight numbers total or less. This ensures accuracy!

Other Important Tire Type Information

LT - Tires for Light Trucks

LT stands for light truck and is a tire designed to be used in heavy duty pickup trucks and other light truck, such as the ones you see on our local roads. LT tires usually require higher inflation pressures than regular passenger tires, and are usually capable of carrying heavy loads.

P - Tires for Passenger Cars

P stands for passenger vehicles. These are tires designed to be used on what you think of as normal cars or other vehicles that require this type of tire, such as minivans and family sedans.

PS - Tires with the Performance System

This is not a speed rating system like P-metric but rather an optional feature added by the manufacturer which allows your car to take advantage of different road conditions through traction control sensors in each wheel that can detect what surface you're driving on and adjust accordingly. The PS symbol may look familiar because it's found on certain new Porsche models – they call theirs PSM (Porsche Stability Management).

ST - Trailer Tires

ST on a tire stands for special trailer tires and means they're designed specifically to be pulled in towing trailers with axels that don't have power, such as utility trailers.

Flotation Tires

Flotation tires are wider, oversized tires designed to carry heavy cargo loads and/or tow trailers on loose surfaces such as sand, gravel, or dirt.

Z - Higher Speed Rating

If you see a Z it means the tire has been tested at speeds over 186 miles per hour!

Find The Right Tires at Pay Later Tires

We have a huge selection of tires and we'll get you the right ones, delivered for free, to your front door or a licensed installer. We guarantee it! 

Click here to start searching for the tires you need at Pay Later Tires.