Find the Best Tires for your car — top-rated and reliable options.
This article is part of our Tires Guide.
The sidewall of your tire is packed with information, but at first glance it can look like a random mix of letters and numbers. Once you know how to read it, that code tells you the tire’s width, sidewall height, wheel diameter, load capacity, speed capability, and more.
If you are shopping for replacement tires, checking fitment, or comparing options online, understanding these markings helps you avoid buying the wrong tire. It also helps you stay within your vehicle manufacturer’s safety requirements, which matters for handling, braking, ride quality, and tire life.
In this guide, you’ll learn how to read a common tire code, what load index and speed rating actually mean, and which sidewall markings matter most for everyday DIY car owners.
Start with the Full Tire Size Code
A common passenger-car tire size looks like this: P215/60R16 95H. That one line contains most of the key information you need. Each section means something specific, and reading it left to right makes it much easier to understand.
- P = tire type
- 215 = tire width in millimeters
- 60 = aspect ratio
- R = radial construction
- 16 = wheel diameter in inches
- 95 = load index
- H = speed rating
Not every tire starts with a P. Some may start with LT for light truck, ST for special trailer, or have no letter at all on certain metric tires. The exact code can vary by tire type, but the layout is similar enough that once you understand one, the others are easier to decode.
What the First Letter Means
Tire Type Prefixes
The first letter, if present, identifies the tire category. For most everyday cars, SUVs, and minivans in the U.S., you’ll usually see P-metric tires. That means the tire is built to passenger-vehicle standards.
- P = Passenger vehicle tire
- LT = Light truck tire, often used on pickups, vans, and some heavy-duty SUVs
- ST = Special trailer tire, not for use on passenger vehicles
- T = Temporary spare tire
If there is no prefix, the tire may still be a standard metric passenger tire, depending on the manufacturer and market. The safest move is to match the type shown on your door-jamb sticker or owner’s manual unless you know exactly why you are changing it.
How to Read Tire Width, Aspect Ratio, and Wheel Diameter
Tire Width
In P215/60R16, the 215 means the tire is approximately 215 millimeters wide from sidewall to sidewall at its widest point. Wider tires can improve grip in some situations, but they may also affect fuel economy, steering feel, road noise, and clearance.
Aspect Ratio
The 60 is the aspect ratio. It tells you the sidewall height as a percentage of the tire width. In this example, the sidewall height is 60% of 215 mm. A lower aspect ratio usually means a shorter sidewall, firmer ride, and sharper handling. A higher aspect ratio usually means a taller sidewall and more ride comfort.
Construction Type
The R stands for radial, which is the standard construction for modern passenger tires. You may rarely see other letters on specialty tires, but for most drivers, R is what you should expect.
Wheel Diameter
The 16 means the tire fits a 16-inch wheel. This number must match your wheel size exactly. A 16-inch tire cannot be mounted on a 17-inch wheel, and vice versa.
When replacing tires, the easiest rule is this: match the tire size listed on your current tire and confirm it matches the Tire and Loading Information sticker on the driver’s door jamb. If the tire on the car now is not the factory size, trust the vehicle sticker and owner’s manual first.
What Load Index Means
The number after the wheel diameter is the load index. In P215/60R16 95H, the 95 is the load index. This number corresponds to the maximum weight a single tire can carry when properly inflated.
The important thing to understand is that the load index is not the weight itself. It is a code that must be looked up on a chart. For example, a load index of 95 equals 1,521 pounds per tire.
Why Load Index Matters
Your replacement tire should meet or exceed the original equipment load requirement. Installing a tire with a lower load index than your vehicle requires can reduce safety margins, especially when carrying passengers, cargo, or towing loads where allowed.
- A higher load index means the tire can carry more weight.
- A lower load index than factory spec is usually not acceptable.
- Load capacity depends on proper inflation, not just the number on the sidewall.
A Few Common Load Index Examples
- 91 = 1,356 pounds
- 94 = 1,477 pounds
- 95 = 1,521 pounds
- 98 = 1,653 pounds
- 100 = 1,764 pounds
- 104 = 1,984 pounds
If your vehicle came with load index 95 tires, you can generally move to a higher load index if the tire otherwise fits and matches manufacturer guidance. But going lower is where trouble starts.
What Speed Rating Means
The final letter in a code like 95H is the speed rating. This indicates the tire’s maximum speed capability under controlled testing conditions when properly loaded and inflated. It does not mean you should drive at that speed on public roads.
Common Speed Ratings
- S = 112 mph
- T = 118 mph
- H = 130 mph
- V = 149 mph
- W = 168 mph
- Y = 186 mph
For everyday use, speed rating also affects more than top speed. Tires with higher speed ratings often have different handling, ride, treadwear, and temperature characteristics. That is one reason why your car may feel different if you install a tire with a very different rating.
Can You Use a Different Speed Rating?
In general, you should use a tire with the same or higher speed rating than the original equipment specification unless your vehicle manufacturer or tire professional says otherwise. Dropping below factory spec can affect handling and safety, and may not be recommended on many vehicles.
Other Important Sidewall Markings You Should Know
DOT Code
The DOT code identifies the manufacturer, plant, and production details. The last four digits tell you the tire’s build date. For example, 2524 means the tire was made in the 25th week of 2024.
Maximum Inflation Pressure
You may see a maximum PSI listed on the tire sidewall. This is not the recommended pressure for your vehicle in normal driving. Use the pressure on the driver’s door-jamb sticker unless you have a specific reason to adjust it.
Maximum Load
This tells you the tire’s rated carrying capacity at a specified pressure. It works with the load index, but again, your vehicle’s recommended tire spec is the best baseline.
M+S and Three-Peak Mountain Snowflake
M+S means mud and snow, which is common on all-season tires. The Three-Peak Mountain Snowflake symbol indicates a tire meets a higher standard for severe snow service. If you live in a snowy region, this symbol matters much more than marketing language.
UTQG Ratings
Many passenger tires list treadwear, traction, and temperature grades. These can help compare tires within broad categories, but they are not as critical for fitment as size, load index, and speed rating.
How to Make Sure You Buy the Correct Replacement Tire
Before ordering tires online or buying at a shop, verify the tire information in more than one place. The sidewall is useful, but the vehicle manufacturer’s sticker and manual are your final authority for original tire sizing and pressure.
- Check the driver’s door-jamb sticker for the original tire size and recommended PSI.
- Confirm the same size, load index, and speed rating on your existing tires.
- Make sure the wheel diameter matches exactly.
- If considering a different size, verify overall diameter, width, clearance, and speedometer impact before buying.
- Replace tires in matching sets when possible, especially on AWD vehicles where tire diameter differences can matter.
If your car currently has a different size than the factory spec, do not assume the current tire is correct. Used cars often come with mismatched or incorrect tires, so check the door sticker every time.
Common Mistakes to Avoid
- Confusing the tire sidewall maximum PSI with the vehicle’s recommended inflation pressure.
- Buying a tire with the right width and diameter but the wrong load index.
- Ignoring the speed rating because you assume it only matters at high speed.
- Mixing very different tire sizes or types on the same vehicle.
- Using old tires with good tread but an unsafe manufacture date.
- Assuming every tire marked 215/60R16 performs the same way. Construction, compound, load range, and speed rating still matter.
A tire can physically fit the wheel and still be the wrong choice for the vehicle. Always look at the full code, not just one or two numbers.
Quick Real-world Example
Let’s decode P225/45R17 91V:
- P = passenger tire
- 225 = 225 mm wide
- 45 = sidewall height is 45% of the width
- R = radial construction
- 17 = fits a 17-inch wheel
- 91 = load index, equal to 1,356 pounds per tire
- V = speed rating up to 149 mph under test conditions
If your car requires this exact specification, replacing it with a tire marked 225/45R17 87T would be a problem because the load index and speed rating are lower. Even though the size looks close enough, it would not properly match the vehicle’s original requirement.
Bottom Line
Reading a tire sidewall gets much easier once you break the code into pieces. The most important parts for replacement shopping are the size, load index, and speed rating. Those tell you whether the tire will fit your wheel, carry your vehicle safely, and meet the intended performance standard.
When in doubt, match the original specification on the driver’s door-jamb sticker and owner’s manual. That simple step prevents a lot of expensive mistakes and helps keep your car safe on the road.
FAQ
Can I Use a Tire with a Higher Load Index than Stock?
Usually yes, as long as the tire size, wheel fitment, and other specs are correct. A higher load index means the tire can carry more weight, but it may also change ride quality or cost more.
Can I Use a Tire with a Lower Speed Rating than the Original Tire?
It is generally not recommended unless the vehicle manufacturer specifically allows it. A lower speed rating can affect handling, heat resistance, and overall performance.
Is the PSI on the Tire Sidewall the Pressure I Should Use?
No. The tire sidewall usually shows the maximum pressure for that tire, not the recommended operating pressure for your car. Use the pressure listed on the driver’s door-jamb sticker.
What Happens if I Choose the Wrong Tire Size?
The wrong size can cause rubbing, incorrect speedometer readings, poor handling, reduced fuel economy, and possible ABS or traction-control issues. In severe cases, it can be unsafe.
Where Can I Find the Factory Tire Size for My Car?
Check the sticker on the driver’s door jamb, the owner’s manual, or the original equipment information from the vehicle manufacturer. Those sources are more reliable than guessing from the current tires.
How Do I Tell How Old a Tire Is?
Look for the last four digits of the DOT code. For example, 2524 means the tire was made in the 25th week of 2024.
Do All Four Tires Need the Exact Same Load Index and Speed Rating?
For most passenger vehicles, matching tires across the axle is strongly recommended, and many vehicles perform best with all four matching. This is especially important on AWD vehicles.
Want the full breakdown on Tires - from costs and replacement timing to DIY tips and how to choose the right option? Head over to the complete Tires guide.