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.
- L - 75 mph
- M - 81 mph
- N - 87 mph
- P - 93 mph
- Q - 99 mph
- R - 106 mph
- S - 112 mph
- T - 118 mph
- U - 124 mph
- H - 130 mph
- V - 149 mph
- W - 168 mph
- Y - 186 mph
- (Y) - more than 186 mph
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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Director, Vehicle Testing
Dave VanderWerp has spent more than 20 years in the automotive industry, in varied roles from engineering to product consulting, and now leading Car and Driver's vehicle-testing efforts. Dave got his very lucky start at C/D by happening to submit an unsolicited resume at just the right time to land a part-time road warrior job when he was a student at the University of Michigan, where he immediately became enthralled with the world of automotive journalism.
Tire Buying and Maintenance Guide
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Example tire number: P215/65R15 95H
The number 215 indicates the tire width in millimeters from sidewall to sidewall, so 215 millimeters in this case. 65 is the aspect ratio code, which means the ratio of its height to width. This tire has a height equal to 65% of its width.
You'll see a number like P215/55R17 97V. The 215 is the width in mm, 55 is the aspect ratio and 17 is the diameter.What do the 3 numbers mean on tire size? ›
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.What does 92y mean on a tire? ›
|Tire size component||What it is||What it means|
|92||Load index||A measurement of how much weight each tire can support. Refer to a load index chart for the total weight allowed.|
|Y||Speed rating||The top speed at which the tire can travel for an extended time. See speed rating table above.|
An arrow points to the numbers 265/70R17 115T on the inner part of the tire sidewall. 265 is the width, 70 is the aspect ratio, R stands for radial, 17 is the wheel diameter and 115T is the load index and speed symbol.How do I read tire codes? ›
The DOT serial number is located on the inside sidewall near the rim. The letters “DOT” are followed by eight to thirteen letters and/or numbers that identify where the tire was manufactured, tire size, and the manufacturer's code, along with the week and year the tire was manufactured.What does 180 55 R17 mean? ›
180/55 ZR 17 M/C (73W) TL. 180. The first number indicates the width of the tyre in millimetres, taken from the widest point of the tyre. 55. The second number indicates the aspect ratio (or height) of the tyre.What's the difference between 225 55 R17 and 225 65 R17? ›
The difference in the dimension of the two tyres is purely in the aspect ratio of the sidewall so the /65 tyres will have a bigger sidewall (note that the number is 65% of the width, not 65 somethings - i.e. 165.75mm vs 140.25mm and that's effectively doubled because you're taking radius, not diameter) and therefore ...Can I use 225 60 17 instead of 215 65r17? ›
Those tires will fit. The diameter difference is very small. All you have to do is roll one over to your car and compare!
A tire's load index is a measurement of how much weight each tire is designed to support. The larger the number, the higher the load capacity. This is one of the most important numbers on your tire. To find out what "95" means, you have to look it up on a Load-Carrying Capacity Per Tire chart.
H-Rated Tires: This is a perfect, average tire for most sedans and commuter vehicles. It might not seem to fit in our chart, but the tire speed rating “H” is rated for up to 130 mph. T-Rated Tires: This tire is often recommended for family sedans and vans. It's rated for up to 118 mph.What does LT mean on a tire? ›
An “LT” on your sidewall before that long string of numbers and letters denoting your tire size signifies the tire is a "Light Truck-metric" size; it was designed for use on a vehicle that carries heavy cargo loads or tows a large trailer.What does Z and R mean in tires? ›
The ZR rating indicates that a tire is capable of high-speed operation, while an R rating indicates that a tire is rated for speeds up to 106 mph. ZR tires are typically used on high-performance vehicles, while R-rated tires are more common on passenger cars.What does the W mean on tires? ›
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).What does SL mean on a tire? ›
“Standard load (SL) tires are intended for normal, everyday use. They will either be marked with 'SL' after the size or not marked at all. Extra load (XL) tires are designed to be able to carry a higher load than Standard Load tires,” explained Mosier of Cooper Tire & Rubber.What does 235 55r19 mean? ›
235 - Tire width in millimeters. 55 - Aspect ratio. The tire's section height as a percentage of its width. R - Tire construction code (Radial). 19 - Rim diameter in inches.What does the 2 digit number on a tire mean? ›
The two-digit number after the slash mark in a tire size is the aspect ratio. For example, in a size P215/65 R15 tire, the 65 means that the height is equal to 65% of the tire's width. The bigger the aspect ratio, the bigger the tire's sidewall will be.What does M and S mean on a tire? ›
M+S stands for Mud+Snow, indicating that the tires are suitable for use in the winter (studded or non-studded winter tires). The official winter tire marking is the snowflake symbol, also known as the 3PMSF marking. (the techinical name is 'Servere Service Emblem".What is the T speed rating on tires? ›