What do numbers on tires mean? Tires are one of the most important components of your vehicle, and understanding the tire number meaning can help you select the right tires for your driving needs and preferences.
To give you the best vision on this subject, we have gathered all the basic essential info about the matter. Let’s delve deeper into it.
In this article:
About The Numbers & Letters On The Tire Sidewall
Novice drivers, you might not be familiar with the string printed on each tire, right? Normally, you will encounter several strings that tell you about the tire type, tire size, load index, speed rating, UTQG rating, and even the manufacture date.
Take my M+S P235/45R18 94V tire for example:
- M+S: for mud and snow terrain
- P: tire type (passenger car)
- 235/45R18: tire size (235mm width, 45% aspect ratio, Radial construction type, 18-inch diameter)
- 94V: Load index of 94, V speed rating
On the same tire, I can also spot a string: DOT 12 34 5210
- DOT: Department Of Transportation
- 12: manufacture code
- 34: the code of the plant where the tire was produced
- 52: week of production – 52nd week
- 10: year of production – 2010
Also, there are other 3 specs on my tire, including treadwear rating (360), traction (A), and temperature (A), which are explained clearly.
Now, let’s dig deeper into each specification and rating.
What Do The 3 Numbers On Tire Size?
The 3 numbers on a tire provide information about the tire’s width (3 first digits), aspect ratio (2 next digits), and wheel size (the last 2 digits).
This number is typically listed in millimeters and indicates the distance between the two tire sidewalls. For example, a tire with a width of 205mm is 205 millimeters wide from sidewall to sidewall. This number can also be listed in inches, but millimeters are more commonly used.
The aspect ratio represents the height of the sidewall as a percentage of the tire’s width. For instance, a regular tire with an aspect ratio of 55 has a sidewall height that is 55% of the tire’s width. A tire with a smaller aspect ratio will have a shorter sidewall, and a greater aspect ratio equals a higher sidewall.
The standard ratio is 75, which holds true on a majority of tires now.
It indicates the diameter in inches of the wheel that can match with the tire. For example, a tire with a wheel size of 16 inches is designed to work on a 16-inch wheel.
Note that the wheel size listed on a tire is not the same as the overall diameter of the tire. The overall diameter of the tire will be larger than the wheel size due to the tire’s sidewall height.
Tire Load Index Brief Explanation
The tire load index chart is a code that represents the maximum load that a tire can safely carry at a specified speed. It is based on a standard set by the Tire and Rim Association, and it ranges from 0 to 279.
Each number on the index corresponds to a specific weight capacity, with higher numbers indicating a higher loading capacity.
For instance, a tire with a standard load index of 95 may securely support up to 1521 pounds. It’s crucial to pick tires whose load indexes match or surpass your automobile’s weight, plus any extra weight from passengers or baggage.
Selecting the incorrect load index could lead to tire failure, poor handling, and other safety problems.
Tire Speed Rating Explain
The speed rating is one of many things to take into account when selecting the correct tires for your car. The greatest speed a tire can safely operate is indicated by its speed rating.
What It Is
The tire speed rating is a letter code representing the highest speed which a tire can safely operate at. It is based on a set of standards established by the Tire and Rim Association and ranges from L (75 mph) to Y (186 mph).
4 most common speed ratings are H, V, T, and W, so let’s see how they differ.
Tire Speed Rating V Vs. W
V and W are two typical tire speed classifications. 149 mph is the maximum speed at which a tire with a V speed rating is safe to drive. Meanwhile, it’s 168 mph for a W-speed-rating tire. High-performance automobiles like sports cars or opulent sedans frequently have tires with these speed grades.
Tire Speed Rating H Vs. T
Another common speed rating for tires is H and T. A tire with an H rating can safely spin at 130 mph, tops. And for a V tire, the number is up to 118 mph. Tires with these speed ratings are often found on standard passenger vehicles and SUVs.
UTQG For Tires
The U.S. Department of Transportation developed the Uniform Tire Quality Grading (UTQG) rating system, which includes these indicators, to assist consumers in making knowledgeable tire purchasing decisions.
What It Is
The UTQG is a rating system that provides information about three important aspects of a tire’s performance: treadwear, traction, and temperature resistance. The sidewall of the tire displays the ratings, which are determined by standardized tests that are administered by the tire manufacturer.
Tire Treadwear Rating
The treadwear rating is a number that indicates how long the tire is expected to last concerning a control tire. To give you an idea, a tire with a 400 treadwear rating is supposed to last 2X as long as one with a 200 rating.
Still, keep in mind that the treadwear rating does not guarantee how long the tire will last, as many factors can affect tire life.
Tire Traction Rating Chart
The tire’s competence to stop on slippery and wet terrain is indicated by the traction rating, which is represented by a single letter code. The ratings range from AA (best) to C (worst), with most tires falling into the A or B categories.
On slick conditions, a tire with a greater traction grade will typically offer more stopping power.
Tire Temperature Rating
The temperature rating is a code of letter that shows how well the tire resists heat. Similar to the traction rating, the categories for temperature grade are A and B, with A being the best and C being the worst.
In most cases, a tire with a greater temperature rating can endure higher temperatures without blowing out or suffering other damage.
Other Tire Markings And Labels
When it comes to choosing the right tires for your vehicle, there are a lot of factors to consider beyond just the size and UTQG rating.
The letter code on the tire type label designates the type of tire. P stands for passenger car, LT stands for light truck, and ST stands for special trailers.
Choosing a tire that is designed for your type of vehicle is necessary as it ensures proper fit and performance.
The marking for the tire’s construction type describes its design. The most typical style of tire construction is known by the initials R, which stands for radial.
Bias-ply, a more traditional kind of construction that is still utilized on some vehicles, is represented by the letter B. Diagonal construction, denoted by the letter D, is a less frequent design.
Sometimes, you might encounter a letter “F” after the symbol of the construction type, which represents a “Run Flat” tire, or “M+S” for mud and snow tires.
The load range marking designates the tire’s maximum load capacity. The load range can range from A (lowest capacity) to F (highest capacity). The range you select should be suitable for the weight and load-carrying requirements of your vehicle.
To locate this info on your tire, find the DOT symbol. The next 4 digits and/or letters indicate the brand and the manufacturing plant. The born-on date will be decoded via the last 4 digits, telling you the week and the year of manufacture.
Why Tire Size Important
Tire size is an essential aspect of your vehicle’s overall performance, safety, and efficiency. The size of your tire impacts everything from your speedometer and odometer readings to your automobile’s handling and stability on the road.
If your tires are too small, they won’t provide enough traction and can lead to poor handling, particularly in wet or icy conditions.
On the contrary, when your tires are too large, they can put extra strain on your vehicle’s suspension and brakes and can even cause damage to the body of your car.
Additionally, suppose you want to replace just one or two tires; you need to ensure they are the same size as the other tires on your car to maintain proper handling and stability.
Frequently Asked Questions
Which One Is Better: Small Or Big Tires?
It depends on your driving needs and preferences, as well as the terrain you’ll be driving on. Smaller tires generally provide better fuel efficiency, handling, and acceleration.
Meanwhile, larger ones can offer better traction and stability in adverse conditions. Thus, the one that is compatible with your car and won’t compromise its performance or safety is the preferable choice.
How Often Should I Change My Tires?
It’s recommended to change your tires every 6 years regardless of the remaining tread depth. However, the frequency also depends on your driving habits, the vehicle type, and the type of tires you are using.
Check your tires’ tread depth regularly and replace them when they reach 2/32 of an inch, which is the legal minimum tread depth in most states.
Can I Change The Tire Size For My Car?
Yes. You can change the tire size if you want. Still, I suggest you consult with a tire professional or refer to your vehicle’s owner’s manual to determine the appropriate tire size for your car.
The Bottom Line
What do the numbers mean on a tire? Now you know the meaning of numbers on tires. Having this knowledge in hand will help maintain optimal performance grade, safety, and longevity.
These three main numbers on your tires can offer useful insight into your tires’ capacities, whether you want to enhance your car’s handling and traction or make sure that your tires can manage big loads or fast speeds.
You may drive with confidence if you spend some time learning about the specs of your tires and are certain that they are the correct fit for your car and your driving requirements.