The three digits following the service type prefix (if present) tell us the cross-sectional width of the tire in millimeters.
In the example above, the tires width, measured from the widest point of the inner sidewall to the widest point of the outer sidewall when properly mounted, is 225 millimeters. The section width can be converted to inches by dividing the width in millimeters by 25.4 like so: (225 millimeters) / (25.4 mm/in) = 8.86 inches.
The two-digit number that usually follows the tire's section width tells us the aspect ratio, or tire profile measurement.
In this example, the 45 indicates that the sidewall distance, from the wheel rim to the outside of the tread, is 45% of the section width. A lower aspect ratio means a lower-profile tire with a shorter sidewall, while a tire with a higher aspect ratio will have a taller sidewall and look more like a donut. Because we know that the tire size shown in this example has a section width of 8.86 inches and the aspect ratio is 45%, the sidewall height for this tire is 3.98 inches: (8.86 inches) x (.45) = 3.98 inches.
Again using our example tire size from above, the 17 means that the tire should be matched to a 17-inch diameter wheel.
Tires usually come in the following widths (in inches): 8, 10, 12, 13, 14, 15, 17, 18, 19, 20, 22, 23, 24, 26, and 28. Tires in these sizes are typically found on most passenger cars, light-duty light trucks, SUVs, minivans, and vans. Tires with a rim diameter measured in inches are called "inch rim" sizes.
In addition to the inch rim sizes, there are also some unique tire sizes out there. Although not as common, tires are made in half-inch diameters for some heavy-duty light trucks, box vans, and heavy-duty trailers. These sizes are usually 14.
5, 15.5, 16.5, 17.5, and 19.5 inches, and an example would be 33x12.5R16.5 118R.
Tires and wheels with unique rim diameters should never be combined with traditional inch rim tires and wheels. Before mounting tires on wheels, the tire and wheel diameters should always be confirmed to match.
When a letter (R, D, or B) follows the two-digit aspect ratio, it tells us the tire's construction. In this example, the R means that the tire has radial construction. Over 98% of all tires sold today are radial tires, where the internal body plies of the tire radiate outward from the center. If there's a D instead of an R, the tire has a bias ply construction, meaning that the internal body plies of the tire crisscross on a diagonal pattern. In belted tires (marked as B), the internal plies crisscross like in a D construction, but there's also an extra layer of reinforcing belts under the tread area.
Belted tires are rarely seen these days.
Today, the only speed rating still included in the tire size is the Z rating (sports cars). Since 1991, all other speed ratings are included in the service description, as shown below.
Since 1991, the service description rating is mandatory for all speed ratings (except Z-rated tires) and appears at the end of the tire's size brand. The service description is used to identify the tire's load index (91 in the example above) and speed rating (V in the example).
For more on load indexes and speed ratings, read Breaking the tire code: Understanding tire service description, load index, and speed rating
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Your vehicle's trim/style
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Want to know how old your tires are or what size your tires are? You need to know how to read tire sidewall information, the alphanumeric code stamped on to the side of your tires. But if you've ever looked at the sidewall of a tire and thought that the blizzard of numbers, letters, and words was as confusing as hieroglyphics, we understand. The alphabet soup on tires' sidewalls can be off-putting, but it's pretty easy once you know what you're looking at.
Beyond the brand (Michelin, Continental, Hankook, etc.
) and model names of the tire, the plethora of data stamped on the sidewall is there largely to satisfy government regulations, which require all manner of information—from when and where the tire was built to how durable it is. Not to worry. Let us be your Rosetta stone to deciphering the language of the tire sidewall. The numbers highlighted in pink on the sample tire below correspond to the explanations that follow.
1) These are some of the most important numbers on any tire, as they tell you how big your tires are. In this case, the tire is 245 millimeters at its widest point (when it's mounted on a wheel of a specified width).
2) The number after the slash indicates its aspect ratio, or profile. This tire's sidewall height is 40 percent of its width.
3) The "R" stands for radial construction (rarer bias-ply and belted tires are denoted by a D and B, respectively).
4) The number 18 indicates that this tire fits an 18-inch wheel. Sometimes, letters precede the first number. A "P" stands for p-metric, which is a tire used primarily on passenger cars. An "LT" indicates a light-truck tire. A "T" means it's a temporary spare. Some tires get a "Z" or an "F" attached to the radial indicator, denoting a Z-rated tire (see service description below) or a run-flat tire.
5) This alphanumeric code is the service description, which provides two key insights into the tire's performance: how much weight it can carry and how fast it can run safely—the latter another good indication of whether it's intended for a family sedan or a hot sporty machine. In our example, the "93" stands for the maximum-load rating of 1433 pounds. The letter W denotes the maximum speed rating, which translates 168 mph—not something intended for mom's minivan. See our list of speed ratings below, which range from a low of "L" (just 75 mph for some off-road tires) to a high of Y (186 mph).
There is also one special ultrahigh speed rating: If a Y-rated tire has parentheses around its service description, say, "(93Y)," that means the tire is rated for speed "in excess of 186 mph." There are also Z-rated tires, but when that designation came out, no one thought a speed rating in excess of 149 mph would ever be needed. By definition, all W- and Y- rated tires are also Z-rated, though not all get a "Z" embossed on the sidewall.
6) Many but not all tiremakers note the heaviest spot of the tire with a red dot. It ultimately has no bearing on tire-and-wheel balance, so it's of little importance.
A tire's alphanumeric codes reveal everything from how fast it can run to where it was built.
7) The numbers after the word "treadwear" indicate (surprise!) the treadwear of the tire, or how long it's likely to last. The higher the number, the more likely it is that you'll get more miles out of it. But the tests that determine tread life are not exact. The experts at tire-seller Tire Rack report that treadwear ratings can vary. They cite the example of two different tires they sell—one from Goodyear and the other from Continental—both of which offer an 80,000-mile tread-life warranty. You'd expect them to have similar, if not identical, treadwear ratings, but the Goodyear's is 740, while the Continental's is 600. So take this number as an indicator, but not an exact predictor, of how long a tire will last.
8‑9) The letter after the word "traction" is a rating that results from a test of how much grip a tire generates when dragged across wet pavement without the tire rotating.
It's not of great relevance to today's cars, which have anti-lock brakes that keep the tires rolling even during emergency braking. The letter following the word "temperature" is an indicator of how well a tire dissipates heat, which increases severely at high speed. Again, it is of less importance than the tire's speed rating, which takes this into account.
10‑11) Some tires carry an "M+S" marking, which stands for "mud and snow." It means that the tire has some added capability in those circumstances because it has a little extra space between its tread blocks. But such tires are absolutely not winter (snow) tires and might not even be conventional all-season tires. That's where the three-peak mountain snowflake icon next to the M+S mark comes in. If a tire has that molded into its sidewall, it has significant snow capability and should be considered a viable winter tire.
12) This area of the tire may display what's called the original-equipment (OE) marking.
Automakers sometimes take a standard, off-the-rack commodity tire and modify its construction or rubber compound to work better on one of their models. So, a Ford Escort and a Chevy Cruze might both be equipped with Firestone Firehawk AS tires that look virtually identical, but each car's tires might differ significantly in ways that affect the ride and handling. If your vehicle's tires carry an OE code, it's best to replace them with the same brand and model of tire wearing the same code—if you can. Tire stores and online retailers can help you with finding tires with the correct OE code for your vehicle.
13) This is a list of the tire's construction materials, of interest primarily to tire engineers and tire geeks.
14) Every tire sold in the U.S. must have U.S. Department of Transportation (DOT) labeling. The first two characters indicate the factory of manufacture, and the next five or six are manufacturer-specific jargon (for tracking purposes, as in the case of a recall).
The last four numbers give the date of production which let you know how old your tires are with the first two digits indicating the week and the latter two the year (for example, "2318" means that tire was produced in the 23rd week of 2018). The European equivalent of the DOT code may also be present (it starts with an "e"), although fewer manufacturers are printing both on a tire's sidewall. If this string of numbers ends with "-S," it means the tire complies with European noise regulations.
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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.
Select tires / tire catalog
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 it is a radial construction tire. 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).
Find tires / tire catalog
Established marking standards allow you to find out the characteristics of a car tire by looking at its sidewall. But not all motorists, especially beginners, can easily "read" the applied designations.
Today we will analyze what tire parameters are and how manufacturers indicate them on their products.
The first and main parameter that you should pay attention to is the numbers on the sidewall.
A popular size for mid-size city cars.
For example, "205/55R16" means that
The manufacturer usually indicates the optimal size for your car in the owner's manual.
The use of tires of a smaller diameter will lead to a decrease in ground clearance, and larger models may simply not fit into the wheel arches.
Tires differ in the way they are tensioned with cord threads: in diagonal ones they are allowed to cross, in radial ones they are not.
The second option is more modern, characterized by increased rigidity and reliability. Designated with the word "Radial" or the letter "R" in the frame size.
Radial tires, due to the larger contact area, provide better traction.
After the standard size, there are load and speed indices, that is, the maximum allowable values for this type of rubber (in our case, “91V”).
In the presented version, the load on one wheel should not exceed 615 kg, and your speed should not exceed 240 km/h.
Choose the load index for a car based on half the maximum weight acting on the axle. Manufacturers recommend choosing tires with a margin of 15-20% of the calculated value.
Also calculate the speed index with a margin of about 15%. Such an amendment is needed due to the fact that the speed of the car can increase on long descents or with a strong tailwind.
Calculate the load index for SUV tires with a margin of 30%.
Tires are divided into winter, summer and all-weather. Manufacturers indicate belonging to a certain type using appropriate inscriptions or images (raindrops, sun rays, snowflakes, etc.). The presence of several images indicates the all-season product.
But the actual allowable load is determined only by the corresponding index. 
Tires without a manufacturer's name may not meet the declared characteristics, and their use may be unsafe. They come in red, green, yellow or white and help you properly install the tires on the car.
Colored stripes help warehouse workers recognize tire sizes and models stacked in stacks.
Most modern tires are tubeless. They are designated "TL" or "Tubeless". Outdated chamber models are labeled "TT" or "Tube Type".
They differ in the way they are attached to the rim of the disc.
Tubeless tires with minor punctures are repaired without removing them from the wheel; also, with periodic pumping, drive to the nearest car service.
During long-term storage, tires lose their elasticity, and their driving performance deteriorates.
But on the models of some manufacturers, you can "read" the year of manufacture and refuse to buy old products.
A 3- or 4-digit code is indicated on the side in a rectangular frame with rounded corners. In the first case, the tire was produced before 2000, in the second - after. The first two digits of the number indicate the week, the last - the year. For example, code 308 means that tires were released in July 98 or 88, 1517 - in April 2017.
Read also: What pressure should be in the tires
In the United States, tires are produced with two different markings.
