You look at the sidewall of a tire and see a string of numbers, letters, and symbols that mean nothing to you. Yet those markings are crucial every time you buy new tires, because the wrong size or an expired DOT date can directly affect your safety and driving performance. This guide covers everything you need to confidently read the markings on any tire.
What the numbers on the tire sidewall mean
Let's take the most common example: the marking 205/55 R16. Each part of that designation has a clear meaning and refers to a specific physical dimension of the tire.
The number 205 indicates the tire width in millimeters, measured from one sidewall to the other when the tire is mounted on the prescribed rim width. A wider tire means a larger contact patch with the road, but also higher fuel consumption and slightly slower steering response. A narrower tire cuts through water better on wet roads but has less grip in dry conditions.
The number 55 is the aspect ratio, the height of the sidewall as a percentage of the width. In this case, the sidewall height is 55% of 205 mm, which works out to roughly 113 mm. A lower number means a lower, sportier tire with sharper handling, but also a less comfortable ride on rough roads. A higher number means a taller sidewall that absorbs bumps and imperfections better.
The letter R stands for radial construction, which is the standard on all passenger vehicles today. The number 16 at the end is the rim diameter in inches. If you have 16-inch rims, you need a tire marked R16.
Load index and speed rating
After the size designation you'll find a marking like 91V or 95H. You need to understand these two values before buying, because they directly affect safety.
The number 91 is the load index, indicating the maximum weight a single tire can support at the prescribed pressure. A load index of 91 means 615 kg per tire, while 95 means 690 kg. Multiply by four tires and you get the total load capacity. If you drive a heavily equipped car or frequently carry a full trunk and passengers, the load index must match or exceed the vehicle manufacturer's specification. A lower index than prescribed means risking tire damage under full load.
The letter V is the speed rating, indicating the maximum speed at which the tire can safely operate under full load. Here are the most common ratings: T means up to 190 km/h, H up to 210 km/h, V up to 240 km/h, and W up to 270 km/h. Never fit a tire with a lower speed rating than the one your manufacturer specified, because it affects vehicle behavior at higher speeds and can be grounds for failing the vehicle inspection.
If you see the marking XL or RF on a tire, it means a reinforced construction for heavier loads. This marking matters for vans, SUV models, and heavily equipped vehicles, as these tires withstand higher pressure and weight without sidewall deformation.
DOT marking and how to check tire age
The DOT marking is something many drivers completely overlook, yet it can save you stress and money. On the tire sidewall, look for the letters DOT (Department of Transportation), and at the very end of that string you'll find four digits inside an oval.
The first two digits indicate the week of manufacture, and the last two the year. For example, the marking 2523 means the tire was produced in the 25th week of 2023, which is late June. A marking of 0819 would mean the 8th week of 2019, or February.
Why does this matter? The rubber compound ages regardless of how many kilometers you've driven. A tire older than 5-6 years loses elasticity and grip, even when the tread visually looks fine. This is especially critical with used tires, where a seller may offer a tire with full tread depth but a DOT date from 2018 or earlier. Such a tire is dangerous regardless of appearance, because hardened rubber drastically increases stopping distance on wet roads.
The DOT marking is sometimes found only on the inner side of the tire, so you can't see it without bending down or lifting the car. During every tire change, we check the DOT date and warn the owner if the tires are older than five years, because on wet roads the difference in braking distance can be several meters.
M+S, 3PMSF, and other seasonal markings
On winter and all-season tires you'll often see the M+S marking (Mud and Snow) and a mountain-with-snowflake symbol known as 3PMSF (Three Peak Mountain Snowflake). The difference between these two markings is significant.
The M+S marking means the tire has a tread pattern suited for mud and snow, but this is a manufacturer's self-declaration and doesn't go through any standardized grip test. Many summer tires with a more aggressive tread pattern carry the M+S marking even though they aren't true winter tires. The 3PMSF marking, on the other hand, means the tire has passed snow testing and meets minimum grip criteria in winter conditions.
In the EU, since November 2024, only the 3PMSF marking is recognized as a winter designation. BiH follows similar regulatory trends, but specific rules may vary between entities, so check the current requirements before buying winter tires. If you're purchasing new winter tires, choose ones with the 3PMSF marking so you're covered regardless of future regulation changes.
Where to find the right size for your car
The easiest place to find the correct tire size for your vehicle is on the sticker located on the B-pillar, the door jamb on the driver's side. Open the door and look at the edge; the sticker is usually at the bottom. It lists the recommended tire size and the prescribed pressure for front and rear tires, often for different load conditions.
Another source is the service booklet or the vehicle's technical documentation. Some manufacturers allow two or three alternative sizes, usually with notes about differences in pressure and handling. If you don't have any of that information, you can also look up the size by the vehicle's VIN number at an authorized dealer.
Never change tire sizes on your own without checking first. Changing the width or diameter affects speedometer accuracy, ABS system operation, suspension geometry, and can cause the tire to rub against the fender at full lock. If you're thinking about a different size, say a wider tire for a better look or a lower profile, make sure your model allows it and in which combinations.
If you're not sure which size fits your car or you want to check the tread depth and age of your current tires, stop by the workshop. It's better to check now than to risk driving on the wrong tires.