Unlocking the Mysteries of Tire Symbols: Discover the Meaning Behind Tire Numbers with Confidence

Last Updated on 3 months

Deciphering the Mystery of Tire Symbols and Codes

You’ll notice a series of numbers and letters when you look at the sidewall of your vehicle’s tires. These tire symbols may seem like a secret code, but they hold valuable information about your tires. Understanding these markings is essential because they detail your tire’s size, type, and capabilities. In this guide, we’ll decode the tire symbols and help you decide when to replace your tires.

Suppose you’ve done a lot of shopping for tires – online or in-store – and you know many styles, types, and designs. Some are easy to understand compared to all-terrain styles, such as winter tires. Others can be more difficult. Many kinds of groupings within tire categories are conveyed with tire symbols. Unless you are an expert in how to read tire codes, chances are that you’ve got some questions about what these symbols mean.

It is essential to understand all of the markings on a tire before you purchase new ones – especially if you are ordering them online. Tires can be a pretty significant investment; plus, the safety and performance of your vehicle depend on the tires you install. A great set of tires will ensure that your car, truck, or SUV can safely drive through inclement weather conditions or improve fuel efficiency.

Why Tire Symbols Matter

Understanding these tire symbols is crucial for several reasons:

1. Safety: Using tires with the correct load capacity and speed rating is essential for safe driving. Overloading or using tires with lower speed ratings can be dangerous.
2. Performance: The right tire size and type can enhance your vehicle’s handling, traction, and fuel efficiency.
3. Compatibility: When it’s time to replace your tires, knowing how to read these tire symbols ensures you get the right ones for your vehicle.
4. Regulatory Compliance: In some regions, using the wrong type of tires may lead to legal issues or voided warranties.

Now that you’ve unlocked the mystery behind tire symbols, you’re better equipped to make informed decisions when it’s time for new tires.

The Basics of Tire Symbols

First, let’s break down the most common tire symbols displayed. These are usually listed in the tire sidewall in the following order to make it easy to understand the details about the tire at a glance.

Tire Type

After the brand name of the tire, there will be a long line containing some numbers and letters. The very first letter listed is the vehicle tire type.

This states what type of vehicle the tire is designed for. Here is what the letters mean:
• P – Passenger
• LT – Light truck
• T – Temporary (spare)
• ST – Special trailer

Tire Width

Next, there will be a three-digit number that indicates the tire width. This measurement is in millimeters and covers the width from the front-facing sidewall to the back sidewall.

Aspect Ratio

After the three-digit tire width, you will notice a front slash (/) symbol followed by another set of numbers. This digit is the aspect ratio, which is the comparison of the width of the tire to the sidewall height. So, say that a tire has the symbol 215/65. This means that the tire’s width is 215 millimeters, and the aspect ratio is 65% of 215. Mathematically, this equates to 139.75 millimeters.

Now, doing that kind of math can be tricky. What’s important to remember is that the ratio impacts the driving experience of the tire. Lower ratios generally have higher performance ratings, meaning that the tires have fantastic handling and are great for high speeds. A higher aspect ratio results in a quieter, smoother ride.

Construction

After the aspect ratio, a single letter representing the tire construction will be listed. There are various construction styles for tires that help to improve their performance for specific vehicles.

Most passenger vehicles use radial tires, represented by the letter R. – this marking is mandated. Radial construction uses cords made from polyester, steel, and fabric coated with rubber, laid perpendicular (or radially) on the tire.

Bias tires can be represented with a B or a D. Bias tires are made with belts with a slant forming an X pattern across the tire. The B stands for bias, and the D stands for diagonal. Unlike radial tires, letter marketing is not mandated for bias tires.

Run-flat tires use a combination of diagonal piles designed to protect the interior from any punctures. Run-flat tires can be identified by the letters RF, RFT, SSR, EMT, or ZP. The variation is due to different manufacturers using different markings.
Trailer tires are commonly marked with an ST – for Special Trailer.

Diameter

The following number states the wheel diameter on which the tire should be mounted. This is typically a two-digit number representing the number of inches between the part of the wheel where the tire will be sealed, known as the bead seat area. This number ranges from 13″ to 24″.

Load Index

Next is the load index number, which will be two or three digits long. Based on a loading chart, this number tells you the maximum weight the tire can support. We will cover this chart in detail later in the post.

Speed Rating

Next will be the tire’s speed rating, again based on a chart. This is represented by a letter that correlates to the tire’s maximum speed capability.
Most vehicle tires have a speed rating that is far higher than the average driver will ever go. This ensures that you can still keep safe control of your vehicle at typical highway speeds – you don’t want to get too close to the maximum speed rating for too long. There’s no need to push your luck!

DOT Symbol

Next is the Department of Transportation (DOT) number code, which proves that this tire model meets the National Highway Traffic Safety Administration’s safety standards.
This code begins with DOT and then is followed by three sets of 4 digits, a combination of letters and numbers. The first two numbers represent the week the tire was manufactured. The second two represent the year. So, if the DOT number is 3620, the tire was manufactured in the 36th week of 2020.

Tire Identification Number (TIN)

The numbers following DOT on the tire are part of the identification numbers. The first step of 4 digits and letters represents the manufacturer and factory where the tires were constructed. Next is the manufacturer-specific coding, which is used for tracking. This number is essential if there is ever a recall listed.
Finally, the last four numbers are the date the tire was produced – as discussed.

UTQG (Uniform Tire Quality Grading)

The US DOT uses the Uniform Tire Quality Grading System to measure the tire’s performance in specific performance categories. The grading rates include:

• Treadwear – This number grades the tire’s wear based on a 7,200-mile vehicle test. The higher the number, the longer the tire will last. This number can be anywhere between 100 to 1000.
•  Traction – This is based on a letter grading scale, and it rates the tire’s braking ability on wet surfaces on a test track. The traction grades are similar to school grading, as they can be AA (the highest), A, B, or C (the lowest).
• Temperature – Next, the tire is rated for the heat resistance it generates when driven at high speeds. The grade ranges from A to C, with A being the best at dispersing heat.
  These values are determined by the manufacturer’s testing facilities – or independent testing agencies hired by the manufacturer.

What Do Tire Size Numbers Mean?

• Now, let’s review the tire size numbers and review them so you know exactly how to read tire size symbols.
• These will be the first set of numbers on the tire sidewall after the letter representing the tire type (P, T, LT, etc.)
• Next will be the set of three numbers measuring the tire’s width in millimeters.
• The 2nd set of numbers is the aspect ratio, which compares the tire’s height to the width.
• Next, there will be a letter representing the tire’s construction with a letter, such as R or B.
• The following numbers state the diameter of the tire in inches.
• These letters and numbers are how you tell tire size quickly and compare it to the requirements for your vehicle.
• Most tire models offer a range of sizes to fit the most common passenger, truck, and SUV models.

What Are Tire Codes?

After the size markings, you will run into the load index and speed index rating codes. These can be a bit more confusing since they require additional charts.

Deciphering the Code

Let’s start with a typical example of a tire symbol you might see: P215/65R15 95H.

1. P – The “P” at the beginning indicates the tire’s type. In this case, it stands for “Passenger.” Other standard designations include “LT” for Light Truck or “ST” for Special Trailer.
2. 215 – This number represents the tire’s width in millimeters. In our example, it’s 215 millimeters.
3. 65 – The aspect ratio is indicated by this number, which represents the tire’s height as a percentage of its width. Here, it’s 65%, showing the sidewall height is 65% of the tire’s width.
4. R – The “R” signifies the tire’s construction type, which is radial in this case. Radial tires are the most common and provide excellent handling and durability.
5. 15 – This number denotes the diameter of the tire in inches. So, the tire in our example is designed for 15-inch wheels.
6. 95 – The load index, represented by a number, indicates the maximum weight the tire can support. In this instance, it’s 95, corresponding to 1,521 pounds (690 kilograms).
7. H – The last letter, “H,” signifies the tire’s speed rating. Speed ratings range from “A” (lowest) to “Y” (highest). “H” corresponds to a maximum speed of 130 mph (210 km/h).

How to Read Tire Codes

The load index code ranges from 60 to 139, which indicates the chart rating of the weight in kilograms and pounds the tire can handle when inflated. It’s essential to remember that this number is the weight load limit for one tire – so if you’re buying a set of 4, the maximum load limit should be multiplied by 4.
To determine this number, look up the code correlation on a load index chart. For example, if the tire has the number “85” on it, the weight load limit is 1,135 lbs. per tire. The weight load limit for a set of four would be 4,450 lbs.

Next is the speed rating, which is indicated by a letter. Some low-speed tires are rated as A1 – A8 –, but these have significantly low-speed ratings. Most passenger, truck, and SUV tires are rated as T, H, V, W, or Z, ranging from 118 to 149 mph.
Again, you can refer to a speed rating index chart to determine the tire’s speed rating.

Understanding Tire Symbols When Buying Tires Online

When buying a tire online, it’s essential to have at least a basic understanding of all these tire symbols to find the right type. Giga Tires offers a handy feature that lets you narrow the selection based on these critical factors.

You can enter the criteria for the tires you need, such as the section width and aspect ratio. This is to make sure you get the right tires. The best way to begin your tire shopping is to get the size of your current tires and input that size to see your available options.

You can filter the results by optional features like brand type, style, category, and season.

Winter Tire Symbols

Winter tires have unique tire symbols, indicating their capabilities and ratings for snowy or icy roads. When buying winter tires, it’s important to note these features to find a model that will keep you safe in extreme driving conditions.

Many winter tires have the M+S rating symbol on the sidewall. This stands for Mud and Snow, meaning the tires are constructed to improve grip on muddy and snowy roads. These tires have a specific block tread pattern, which helps to improve traction.

Just because a winter tire has an M+S rating does not necessarily mean it is safe to use in inclement weather. The M+S test is not very in-depth by today’s standards (like freezing temperatures and ice.

It only measures a tire’s performance in packed snow and mud. It does not indicate how well the tire performs in thick, freshly fallen snow, dry, frozen roads, ice, or loose snow and mud. You may also see a unique tire symbol resembling a three-peaked mountain with a snowflake inside.

The Three Peaks Mountain Snowflake symbol indicates that the tire is rated for “severe snow service,” which is a far more reliable way to determine a winter tire’s safety rating.

These tires undergo a far more rigorous test to measure the traction performance on many types of roads, including slippery, low temperatures, and freezing surfaces.

Finding the exact style, type, and size of tire for your vehicle can be overwhelming. There are a lot of tire symbols to consider here! But knowing how to read tire codes and understand what the numbers and tire symbols mean will make it far easier to narrow down your options.

Our team at Giga Tires is on hand to answer any questions regarding tire codes, sizes, and styles. Please contact our team today to help find the exact fit for your vehicle!

Conclusion

In conclusion, understanding tire symbols and the meaning behind the numbers on a tire is the key to informed tire selection. These symbols are not just random markings; they hold vital information about your tire’s size, type, and performance capabilities. By decoding the tire symbols, you can ensure your vehicle’s safety, optimize its performance, and stay compliant with regulations.

When it’s time to replace your tires, knowing the significance of these numbers empowers you to make the right choice. So, don’t let tire symbols mystify you—embrace the knowledge and choose your tires wisely for a safer and smoother ride.

Ready to find the perfect tires for your needs? Shop Now at Giga Tires

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At Giga Tires, we offer a wide selection of tires with clear labeling, making it easy to find the perfect match for your vehicle. Don’t leave your tire choice to chance—shop confidently at Giga Tires.

Discover a treasure trove of tire-related insights! Don’t miss out on more valuable articles waiting for you at Giga Tires’ website.

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FAQs

What do the numbers on tires mean?

The numbers on tires provide essential information about the tire’s size, load capacity, speed rating, and more. For example, the first number represents the tire’s width in millimeters, while the second indicates the aspect ratio (height to width). The third number is the tire’s diameter in inches, and subsequent tire symbols and numbers convey additional details.

What do the three numbers on tire size mean?

The three numbers on tire size represent its width, aspect ratio, and diameter. For instance, if you see a tire size like 205/60R16, the first number (205) is the width in millimeters, the second number (60) is the aspect ratio, and the third number (16) is the diameter in inches.

How do you read tire numbers?

Reading tire numbers involves understanding the sequence of information. Start with the width, the aspect ratio, then the diameter. Additionally, tire symbols and letters might indicate speed ratings and construction type. Refer to your tire’s sidewall for a full breakdown of its code.

What do the letters and numbers mean in the tire code?

The letters and numbers in the tire code convey various details. Letters often represent speed ratings (e.g., “H” for high-speed). Numbers indicate load capacity, construction type (e.g., “R” for radial), and manufacturing information. Understanding these elements helps you select the right tires for your vehicle and driving style.