How to Read a Tire Sidewall: Size, Load Index and Speed Rating

A tire sidewall is more than a strip of rubber with a brand name on it. The letters and numbers molded into the side of a tire identify its size and construction, describe important limits, and help distinguish one tire from another. Knowing how to read those markings makes it easier to compare tires, check the tire on your vehicle, and have a clearer conversation when you need service.

The sidewall does not tell the whole story about whether a tire is right for a particular vehicle. Vehicle manufacturers specify appropriate tire sizes and service characteristics, and the placard on the driver’s door area is an important reference. A basic understanding helps prevent common mix-ups.

Start with the tire size sequence

Many passenger tires use a size description that looks like P215/60R16 94H. Read it as a group rather than as one long number. Each part describes a different feature of the tire.

Service type: the first letter

The first letter, when one appears, indicates a service type. A P commonly identifies a passenger tire. LT commonly identifies a light-truck tire. Some metric tire sizes start directly with the width and do not include a leading letter. Service type matters because a tire built for a light truck may use different load conventions from a passenger tire of a similar size. Do not assume that two tires are interchangeable just because the diameter looks close.

Section width: 215

In the example, 215 is the nominal section width in millimeters: the approximate width of the tire at its widest point when mounted on its specified measuring rim. It is not the tread width, and it is not a promise that every 215 tire will measure identically. Design differences and wheel width can affect the installed measurement. The number is most useful as part of the complete size, not by itself.

Aspect ratio: 60

The number after the slash is the aspect ratio. Here, 60 means the sidewall height is approximately 60 percent of the section width. A lower aspect ratio generally means a shorter sidewall relative to the tire’s width. For example, a 215/60 tire and a 215/45 tire have the same nominal width but different sidewall heights. That difference can affect overall tire diameter, ride characteristics, clearance, and the way the vehicle’s systems behave.

Construction: R

The R means radial construction, which is common on modern road-going tires. In a radial tire, the body cords are arranged in a way that differs from bias-ply construction. This letter is a construction descriptor, not a wheel size or a performance grade. Other construction letters may appear on some tires, so it is best to read the complete marking rather than focusing only on the R.

Wheel diameter: 16

The final number in the size portion, 16, is the wheel diameter in inches that the tire is designed to fit. It must match the wheel diameter. A tire with a 16-inch wheel-diameter marking cannot be installed on a 17-inch wheel, even if other numbers seem similar. This mixed use of millimeters for width and inches for wheel diameter is one reason sidewall markings can look confusing at first.

Understand load index and speed rating

After the basic size, the example shows 94H. These are the load index and speed symbol. They provide additional information about the tire’s capability when it is used within its stated conditions. They should be considered along with the vehicle manufacturer’s specifications, not as isolated upgrade labels.

Load index: 94

The load index is a coded number that corresponds to a maximum load capacity in a standardized table. It is not a weight in pounds or kilograms written directly on the tire. A higher number corresponds to a higher listed load capacity, but the proper choice depends on the vehicle, axle requirements, tire pressure, and the manufacturer’s recommendation. Replacing tires with a lower load index than specified may not provide the intended capacity. A tire professional can help compare the tire’s markings with the vehicle placard and owner’s information.

Speed symbol: H

The speed symbol is a letter associated with a tested speed category under specified conditions. It does not mean a driver should operate at that speed, and it does not override posted limits, road conditions, tire condition, inflation, load, or safe-driving judgment. The symbol helps identify the performance category designed for the tire. When replacing tires, maintaining the vehicle manufacturer’s specified rating is generally the sensible starting point unless a qualified professional advises otherwise.

Find the maximum load and cold inflation statement

Most sidewalls also state a maximum load and a maximum inflation pressure. These lines are frequently misunderstood. The maximum pressure molded on the tire is not automatically the recommended everyday pressure for the vehicle. It is the maximum cold inflation pressure for the tire itself under its rating conditions.

For normal inflation guidance, look for the vehicle tire-information placard—often located on the driver’s door jamb or door edge—or consult the owner’s manual. The placard usually lists the recommended cold inflation pressure and original equipment tire size for the vehicle. “Cold” means the vehicle has been parked long enough for the tires to return close to ambient temperature. Checking pressure after a long drive can produce a higher reading because tires warm during use.

Use a reliable gauge and follow the vehicle’s specified front and rear pressures if they differ. Do not lower or raise pressure simply to match a number noticed on the tire sidewall. If a tire repeatedly loses air, has visible damage, or shows unusual wear, it needs inspection rather than repeated inflation alone.

Read the DOT tire identification number and date code

Tires sold for road use in the United States carry a DOT tire identification number. The sequence begins with DOT and includes plant, tire-size, and manufacturer-specific information. The complete number may be molded on only one side of the tire, so it is sometimes necessary to look at the inward-facing sidewall.

The final four digits indicate the week and year of manufacture. For example, 2325 means the tire was made in the 23rd week of 2025. This date code is useful when identifying tires for recalls, understanding their age, or discussing an inspection. Age is only one part of tire condition. Storage, climate, use, maintenance, damage, and visible cracking can all matter. If you are unsure whether an older tire remains appropriate for use, have it evaluated by a qualified tire professional.

Other markings you may see

Sidewalls contain additional labels that can be useful but are easy to overinterpret. M+S generally indicates a mud-and-snow tread designation. A three-peak mountain snowflake symbol indicates a tire meets a separate snow-traction performance requirement. Neither marking removes the need to drive for current conditions or to follow local requirements.

XL or “Extra Load” may identify a tire built to carry more load at a specified pressure than a standard-load tire of the same size. Run-flat markings vary by manufacturer and indicate a design intended to provide limited mobility after some pressure loss under specified conditions. Directional tires may have an arrow showing the required rolling direction; asymmetric tires may be marked “outside” and “inside.” These installation markings are critical because mounting them incorrectly can affect their intended performance.

You may also see Uniform Tire Quality Grading information, such as treadwear, traction, and temperature grades, on many passenger tires. These grades are comparative and have defined testing contexts; they should not be treated as a prediction of exact mileage or as a complete measure of tire quality. A tire’s intended use, fitment, handling needs, climate, and maintenance all remain relevant.

Use the sidewall to compare, not to self-diagnose

Reading a sidewall is helpful when comparing what is on the vehicle with a replacement option. Start by recording the complete size, load index, speed symbol, and any special markings. Then compare that information with the vehicle placard and owner’s manual. A difference may be intentional, but it is worth understanding before purchasing or installing tires.

A sidewall cannot diagnose an alignment issue, suspension problem, leak, vibration, or internal tire damage. Look for obvious concerns such as cuts, bulges, exposed cord, deep cracks, or a tire that will not stay inflated, but avoid making assumptions about safety based only on appearance. Tire concerns can involve internal damage that is not visible from the outside. A trained inspection is the right next step when something seems wrong.

FAQ: reading tire sidewall markings

Where can I find my vehicle’s correct tire pressure?

Check the vehicle tire-information placard, often in the driver’s door area, or the owner’s manual. The maximum pressure shown on the tire sidewall is not necessarily the vehicle’s recommended cold inflation pressure.

Can I replace one tire with a different size?

Changing size can affect clearance, handling, speedometer readings, vehicle systems, and load capability. Confirm fitment and manufacturer guidance with a qualified professional before making a change.

Is the DOT date code the tire’s expiration date?

No. It identifies the manufacturing week and year. Tire suitability depends on condition, use, storage, visible damage, and applicable manufacturer guidance, not the date code alone.

What does a bulge on the tire sidewall mean?

A bulge can indicate damage and should be inspected promptly. Avoid relying on a tire with a visible sidewall bulge until a qualified tire professional has evaluated it.

Do all four tires need the same speed rating?

Vehicle and tire manufacturer guidance should lead the decision. Matching the specified tire characteristics across the vehicle is generally important for predictable handling, but the right answer can depend on the vehicle and tire setup.