Tire size can be confusing. Some numbers on the sidewall are listed in millimeters while others are inches. Plus, the right size for your car, truck, or trailer can differ depending on where and how you drive.
You can see your original equipment tire size in your owner’s manual or on the placard generally located on the driver’s side door jam. This is the sizing recommended by the vehicle manufacturer.
If you’re interested in switching out your tires for a different look or performance, a good place to start is the numbers and other indicators on your existing tires’ sidewall. Next, have a tire professional help you determine a tire size range that will fit your vehicle and driving needs.
Here’s what those numbers and indicators on the sidewall indicate and how to understand them:
A: TIRE TYPE The first letter in the code tells you what class of tire it is.
P stands for passenger vehicle tire. P-class tires include cars, SUVs, crossovers, minivans and smaller pickup trucks.
LT means light truck tire, designed for vehicles that are capable of carrying heavy loads, towing trailers, or for those looking for an extra heavy duty option. These are often equipped on three-quarter or 1 ton trucks and SUVs.
ST stands for Special Trailer. These tire sizes are meant for trailers, including fifth wheels and other travel trailers, as well as boat and utility trailers.
If there’s no letter before the first number, you have a metric tire most commonly referred to as European size. It’s also measured in millimeters but may have a different load capacity than a P or LT tire.
B: TIRE WIDTH The three-digit number following the letter is the tire’s width (from side to side, looking at the tire head on) in millimeters. This may also be referred to as the section width.
C: ASPECT RATIO The forward slash separates the tire width number from the two-digit aspect ratio. The bigger the aspect ratio, the higher/taller the tire’s sidewall, or “profile” as it’s sometimes called.
The aspect ratio is indicated on the tire sidewall as a percentage. It’s the height of the sidewall measured from wheel rim to top of the tread, expressed as a percentage of tire width.
In this example, the aspect ratio is 65, meaning the sidewall is 65 percent as high as the tire is wide. To get the sidewall height, take the tire width of 215 mm and convert it to inches (8.46). Then multiply this by 65% (.65). This gives you an answer of 5.5, the sidewall height in inches.
D: CONSTRUCTION TYPE This single letter tells you about the internal construction of the tire.
R is for radial tires, the industry standard for most tires today. They have better road grip, lower rolling resistance for better gas mileage, ride comfort and durability than previous generations of tires.
In a radial tire, the plies — layers of strong cords made of a blend of polyester, steel and fabric and coated with rubber — are laid perpendicular to the direction of travel.
D is for tires built with diagonal (crisscrossed) plies, called bias-constructed tires. They are also called conventional, x-ply, or cross-ply tires. Some motorcycle and trailer tires still use this internal construction.
Some run-flat tires are identified with an F followed by the type of internal construction.
E: WHEEL DIAMETER This two-digit number specifies wheel diameter in inches. It’s the distance between the two bead seat areas (where a tire gets tightly sealed onto the wheel).
F: LOAD INDEX The two-digit or three-digit number that follows the gap specifies tire load index. The load index symbol indicates how much weight a tire can support, based on the following standard chart. In our example, the load index is 89, which indicates the tire has a load capacity of 1,279 pounds, when inflated to the tire’s maximum air pressure rating.
G: SPEED RATING The last letter is the tire speed rating. This indicates the top speed it’s safe to travel at for a sustained amount of time. A tire with a higher speed rating can handle heat better and provide more control at faster speeds. The maximum operating speed of a vehicle is no more than the lowest speed rating of all tires mounted on the vehicle. (Of course, you should always abide by speed limits for safer driving.) Speed rating is usually, but not always, a single letter (see the chart).
Below you will find several charts that will help you understand tire sizing numbers, including a load index chart and speed rating chart.
A tire size calculator is a quick way to see whether the tire size you’re considering will likely fit your car, SUV, sports car, light truck or crossover.
But remember that is only an estimate. It’s important to stay within the sizing tolerances of your vehicle.
Tires that are the wrong size could cause some pull in the steering wheel, rub against the suspension or body of your vehicle, reduce clearance on hills, or result in a stiffer or noisier ride.
If you’re considering mounting a different tire size on your vehicle, check with a tire expert. Find out whether the tires and wheels you have your eye on are the right fit for your vehicle’s suspension, gearing, and bodywork. And ask how any differences in revolutions per mile, tire speed, load index, and speed rating will affect your ride quality and vehicle performance.
See how new tires and rims will look on your car or truck using our Virtual Wheels simulator, available at any Les Schwab.
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Tires
What would you say if you had to describe your tires in a few words? You might say something like, “They’re black, grooved, rubbery, and round.
” While you’re certainly right, you’re missing some key information—and it’s printed right on the tire! Find out what your tire numbers mean so you can make the best, most informed decisions about your tire and car care.
For the purpose of this piece, let’s pretend we’re looking at a tire with 215/65 R15 printed on its sidewall. What do the numbers on this tire mean?
“215” in this sequence refers to the tire’s width in millimeters. In other words, this tire is 215 millimeters wide, from sidewall to sidewall.
“65” in the sequence is the aspect ratio of the tire. The aspect ratio is a percentage, and it tells you the ratio of the tire’s height to its width. In this example, the aspect ratio number “65” means that the tire’s height is 65 percent of its width.
The “R” in this sequence refers to the construction of this tire.
Specifically, the “R” means that the layers run radially across the tire. The majority of tires on the road today are radial tires, in which the internal layers are perpendicular to the axis of rotation (and the direction of travel).
The other letter you might see here is a “D,” which denotes a tire that has a diagonal or bias ply construction. These tires have plies that are laid out in a diagonal, or crosshatch, pattern.
The very last number in the sequence, “15,” is the diameter of the tire. This is an important number—this is the number you’ll refer to when you need to know your tire size! The “15” indicates that this particular tire would fit a rim with a 15-inch diameter.
Now that you know how to read numbers on tires, you'll be able to describe your tires with much more knowledge and accuracy than, “black, grooved, rubbery, and round.” Check out our latest tire deals and head to your nearest Firestone Complete Auto Care to chat it up with people who speak tire, too! Our technicians are here for everything you need, from tire repair to tread depth checks.
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Do you want to choose a tire for your car, but do not understand tire markings well? It's not a problem! In this section, we will help you figure out what tire parameters are, what they mean, and which tire is right for your car.
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195/65 R15 91 T XL
195 is the tire width in mm.
65 - Proportionality, i.e. profile height to width ratio.
In our case, it is equal to 65%. Simply put, with the same width, the larger this indicator, the higher the tire will be and vice versa. Usually this value is simply called “profile”.
Since the tire profile is a relative value, it is important to take into account when choosing rubber that if you want to put tires with a size of 205/65 R15 instead of the size 195/65 R15, then not only the width of the tire will increase, but also the height! Which in most cases is unacceptable! (except when both of these sizes are indicated in the car's operating book). You can calculate the exact data on changing the outer dimensions of the wheel in a special tire calculator.
If this ratio is not specified (for example, 185/R14C), then it is equal to 80-82% and the tire is called full profile. Reinforced tires with this marking are usually used on minibuses and light trucks, where a large maximum wheel load is very important.
R - means a tire with a radial cord (in fact, almost all tires are made this way now).
Many mistakenly believe that R- means the radius of the tire, but this is the radial design of the tire. There is also a diagonal design (indicated by the letter D), but recently it has practically not been produced, since its performance is noticeably worse.
15 - wheel (rim) diameter in inches. (It is the diameter, not the radius! This is also a common mistake). This is the “landing” diameter of the tire on the disk, i.e. is the inside size of the tire or the outside of the rim.
91 - load index. This is the level of maximum permissible load on one wheel. For passenger cars, it is usually done with a margin and is not a decisive factor when choosing tires (in our case, IN - 91 - 670 kg.). For minibuses and small trucks, this parameter is very important and must be observed.
T is the tire speed index. The larger it is, the faster you can ride on this tire (in our case, IS - H - up to 210 km / h).
Speaking about the tire speed index, I would like to note that with this parameter, the tire manufacturer guarantees the normal operation of the rubber when the car is constantly moving at the specified speed for several hours.
There are two different American tire markings. The first one is very similar to the European one, only the letters “P” (Passanger - for a passenger car) or “LT” (Light Truck - light truck) are placed before the size. For example: P 195/60 R 14 or LT 235/75 R15. And another tire marking, which is fundamentally different from the European one.
Example: 31x10.5 R15 (corresponds to European size 265/75 R15)
31 is the outside diameter of the tire in inches.
10.5 is tire width in inches.
R - a tire with a radial design (older tire models were with a diagonal design).
15 is the inner diameter of the tire in inches.
Generally speaking, except for inches that are unusual for us, the American tire marking is logical and more understandable, unlike the European one, where the height of the tire profile is not constant and depends on the width of the tire. And here everything is simple with decoding: the first digit of the standard size is the outer diameter, the second is the width, the third is the inner diameter.
XL or Extra Load is a reinforced tire, the load index of which is 3 units higher than that of conventional tires of the same size. In other words, if a given tire has a load index of 91 marked XL or Extra Load, then this means that with this index, the tire is able to withstand a maximum load of 670 kg instead of 615 kg (see the table of tire load indices).
M+S or tire marking M&S (Mud + Snow) - mud plus snow and means that the tires are all-season or winter.
Many summer tires for SUVs are labeled M&S. However, these tires must not be used in winter, as winter tires have a completely different rubber compound and tread pattern, and the M&S badge indicates good flotation performance.
All Season or AS all season tires. Aw (Any Weather) - Any weather.
Pictogram * (snowflake) — rubber is designed for use in harsh winter conditions. If this marking is not on the sidewall of the tire, then this tire is intended for use only in summer conditions.
Aquatred, Aquacontact, Rain, Water, Aqua or icon (umbrella) Special rain tires.
Outside and Inside ; asymmetric tires, i.e. It is important not to confuse which side is the outside and which is the inside. When installing, the Outside inscription must be on the outside of the car, and Inside on the inside.
RSC (RunFlat System Component) - RunFlat tires are tires on which you can continue to drive a car at a speed of no more than 80 km / h with a FULL tire pressure drop (due to a puncture or cut).
On these tires, depending on the manufacturer's recommendations, you can drive from 50 to 150 km. Different tire manufacturers use different designations for RSC technology. For example: Bridgestone RFT, Continental SSR, Goodyear RunOnFlat, Nokian Run Flat, Michelin ZP etc.
Rotation or arrow This marking on the tire sidewall indicates a directional tire. When installing the tire, you must strictly observe the direction of rotation of the wheel, indicated by the arrow.
Tubeless - tubeless tire. In the absence of this inscription, the tire can only be used with a camera. Tube Type - indicates that this tire must be used only with a tube.
Max Pressure ; maximum allowable tire pressure. Max Load - the maximum allowable load on each wheel of the car, in kg.
Reinforced or the letters RF in the size (for example 195/70 R15RF) means that this is a reinforced tire (6 layers). The letter C at the end of the size (for example 195/70 R15C) indicates a truck tire (8 layers).
Radial this marking on the rubber in the standard size means that this tire is a radial design. Steel means that there is a metal cord in the tire structure.
Letter E (in a circle) - the tire meets the European requirements of ECE (Economic Commission for Europe). DOT (Department of Transportation - US Department of Transportation) is an American quality standard.
Temperature A, B, or C The temperature resistance of the tire at high speeds on the test bench (A is best).
Traction A, B, or C
Treadwear ; relative expected mileage compared to a specific US standard test.
TWI (Tread Wear Indiration) - tire tread wear indicators. The marking on the TWI wheel can also be with an arrow. Pointers are located evenly in eight or six places around the entire circumference of the tire and show the minimum allowable tread depth. The wear indicator is made in the form of a protrusion with a height of 1.
6 mm (the minimum tread value for light vehicles) and is located in the tread recess (usually in the drainage grooves).
DOT - Manufacturer's coded address, tire size code, certificate, issue date (week/year).
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In this article:
Are you looking for a set of summer or winter tires for your car but don't understand all those numbers and letters? This problem is easily solved. In this article, we will show you how to easily and quickly understand what the numbers on the tires mean, what parameters are hidden behind them, and which tires are suitable for your car.
Only then the car will confidently stay on the road when it is shod with rubber with optimal technical characteristics corresponding to the weather, type of coverage and season.
The marking of car tires consists of several meanings. For example, on any wheel, the manufacturer, brand of rubber, and tire size are indicated. The first three numbers on the wheel indicate the size of the rim (in inches, 1 inch equals 2.54 cm), how wide the tire is, and the height of the profile. This marking can be seen if you look at the wheel from the outside.
Photo: Shutterstock
Let's analyze what the numbers on the tires mean on a specific example of a wheel marked 195 60 R16. The first digit of 195 mm is the tread width. What does the second number on a tire label mean? It shows the relationship between tread height and tire width. The wheel will cling to the coating perfectly if the value of this index is high. Most often, drivers call this parameter the height of the profile.
The last number is the inner diameter of the tire (in inches). Many car owners make the following mistake: they buy tires without taking into account the fact that external parameters change.
So, the height of two wheels marked 185 65 R15 and 210 65 R15 will be different, but the landing diameter is the same. Due to small differences in the profile height and tire width in this example, it will not be possible to mount tires on a car. This should not be forgotten when buying a set of wheels. You can use the tire calculator to find the right tire size for you.
In addition, one more parameter is applied to any wheel, this is the permissible speed. It is located after the numbers on the tires indicating the tire size. This index indicates what maximum speed the tire is designed for.
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What do the numbers on the tires after the speed index mean? Usually there is an indication of the permissible load on one tire.
For example, it may look like this: "88T". This figure means that when driving at the maximum possible speed of 190 kilometers per hour, the load on one wheel should be no more than 560 kilograms.
Photo: Shutterstock
To make it clearer what the numbers on the tires mean, consider the European marking of the Cordiant Sport 3 225/65 R17 106H tire model.
On American tires, you can find two different types of markings that differ from each other.
Consider the first marking: P 195/60 R 14 or LT 235/75 R15. As you can see, it practically does not differ from the European one. However, the size is preceded by the letter P on passenger tires or LT on tires for light trucks.
There is also a second marking, it looks different: 31x10.5 R15. In this case, the usual European marking would look like this: 265/75 R15.
What do the numbers on tires with this marking mean (in inches):
It is worth noting that if you do not pay attention to the units of measurement (inches, which are unusual for us), then the American marking will be clearer and more logical in comparison with the European one. Indeed, in the second case, the height of the rubber profile depends on the width of the wheel.
In the American labeling, everything is simpler. For clarity, consider what the first digit in tire size means. It shows the size, that is, the outer diameter. The second number indicates the width, the third - the inner diameter.
You can follow the current promotions on the Halva Installment Card, which will help you profitably purchase the goods you need, here.
How to find out the width of the tire in the usual units of measurement, that is, in mm? To do this, multiply the width in inches 10.5 by 25.4, because one inch equals 2.54 cm. The result is a value of 267 mm. Since there is no given size, we take into account the width of the tire 265, which is obtained after rounding.
The next step is to find out the height of the sidewall, which is measured as a percentage. To do this, perform the following steps: subtract the bore diameter from the outer diameter. Then we divide the resulting value by 2. The figure that we get, then needs to be divided by the width of the profile.
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Thus, in our example, we have the following: ((31 - 15) : 2) : 10.5 = 0.76. The resulting value must be rounded up to 75.
As a result, we will have the following markings on tires: 265/75 R15.
If the profile height is not indicated on the tire, do not forget that for passenger tires this figure is 80 - 82%, for trucks 88%.
To convert from metric to inch system, we need to perform calculations:
So, we figured out what the numbers on tires with the American marking mean 31 * 10.
5 R15
Photo: Shutterstock
XL or Extra Load - this inscription on the wheels means that they are reinforced, that is, the load index is more than 3 units, compared to standard tires with the same size. Simply put, when you see a load index of 9 on rubber1, as well as the inscription XL, which means that this tire is designed for a load of not 615 kg, but 670. For clarity, it is recommended to study the load index plate.
M+S , M&S ("mud and snow") means that the tires are designed for winter (or all-weather). This marking can also be seen on summer wheels for SUVs. But in this case, rubber is not suitable for use in winter, since winter tires have a different composition, as well as a specific tread pattern. "M&S" means you have an off-road wheel in front of you.
All Season or AS, ("for all weather") - all-weather tires.
The snowflake badge indicates that the tires are designed for winter use. Don't see this marking on the side of the tire? So, you can ride on such tires only in the summer.
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Aquatred, Aquacontact, Rain, Water, Aqua or the symbol "umbrella" - means that you have rain tires in front of you.
Outside and Inside the inscription indicates that these are asymmetrical tires. When installing them on the car, you should be extremely careful, because they have an outer and inner side. During installation, pay attention to the fact that the inscription "Outside" is located outside, "Inside" - from the inside.
RSC, RunFlat - on such rubber, even if a puncture occurs, you can continue driving at speeds up to 80 kilometers per hour. These tires allow you to drive a distance of 50 - 150 km after the pressure has completely dropped. Depending on the manufacturer, the marking may vary slightly, for example Bridgestone RFT, Continental SSR, Goodyear RunOnFlat, Nokian Run Flat, Michelin ZP.
Rotation or the "arrow" icon on the side of the tire means that you have a directional tire in front of you.
When mounting it, you should take into account the direction of rotation of the wheel, which is indicated by the arrow.
Tubeless - wheel without a chamber. If there is no such marking, the tire can only be used with a tube. The inscription Tube Type means that rubber can only be used with a camera.
Max Pressure is the highest allowable pressure in the wheel, Max Load is the maximum load capacity (kg) that the tire is designed for.
Reinforced, RF (for example, 195/70 R15RF) means that the tire is reinforced, it has 6 layers. When the letter C is at the end of the marking (for example, 195/70 R15C), which means that this rubber is cargo and it has 8 layers.
Radial – The inscription indicates that the tire has a radial construction. If there is the word "Steel", then the tire is reinforced with a metal cord.
Letter E, circled - rubber meets European ECE standards. The inscription DOT means that the tire meets the American quality standard.
Temperature (A, B or C) - shows how rubber is resistant to high temperatures when driving at maximum speed. When the letter A is indicated, then the heat resistance is the best.
Traction (A, B, C) - indicates how well the tire will brake on wet roads.
Treadwear – The inscription indicates the relative mileage of the tire.
TWI (Tread Wear Indiration) - means tread wear indicator. Most often, next to this inscription is the sign "arrow". Characters distributed in 6 – 8 sections all over the wheel. They indicate the smallest tread depth at which the tire is allowed to operate. The wear indicator protrudes 1.6 mm. This is the minimum allowable tread height for passenger tires. The wear indicator is located in a recess in the tread, most often in the grooves to drain water.
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DOT - manufacturer's address code, coded tire size, certificate, and the week and year the tire was manufactured.
We have analyzed what the numbers mean on winter tires, as well as on summer and all-season tires. However, in addition to them, there is also a color marking, the meaning of which also needs to be known. Usually on tires you can see various symbols of four colors: red, yellow, white and blue.
Photo: Shutterstock
The most commonly used white label is . For example, you might see icons in a small circle. The white marking is applied by a specialist when checking the compliance of the tire with quality standards. If this symbol is present, it means that the product has been checked by the technical control department.
Red marker can have two meanings. Usually rubber, which has such a marking, is installed at the factory. A small red circle indicates that the tire is the heaviest in this place.
The yellow marker indicates the lightest area of the tire.
