When you glance at your tire, it might just look like a big round piece of rubber that gets you from point A to point B. But if you look closer—right on the sidewall—you’ll notice a series of numbers, letters, and codes that look a little like a secret language. And in a way, they are.
Those tire sidewall markings are packed with important information about your tire’s size, capabilities, and performance limits. Knowing how to read them isn’t just a “car enthusiast” thing—it directly affects your safety, fuel efficiency, and even how smoothly your vehicle drives.
At Burt Brothers Tire & Service, we know that most drivers don’t think about their tires until there’s a problem. That’s why we’re here to make decoding those tire codes easy, approachable, and useful—so you can feel confident about your vehicle’s safety and performance every time you hit the road.
What Is a Tire Sidewall and What Information Does It Hold?
The sidewall is the outer portion of your tire that faces you when the tire is mounted on your car. It’s not just a smooth piece of rubber—it’s essentially your tire’s ID card.
On every sidewall, manufacturers include key specs such as:
- Tire size
- Load index and speed rating
- Tire construction type
- DOT (Department of Transportation) manufacturing code
- Seasonal designations (like M+S or the Three-Peak Mountain Snowflake)
- Maximum inflation pressure and load information
- Performance ratings for treadwear, traction, and temperature
These markings aren’t random—they’re standardized by law so that drivers, mechanics, and tire retailers all “speak the same language” when it comes to tire fitment and safety.
How to Read Tire Size: Breaking Down the Code
Let’s start with the most common thing you’ll see: tire size. Take this example:
P215/65R15
Here’s what each part means:
- “P” → Stands for “Passenger Vehicle.” Other options might be “LT” for light truck or “T” for temporary spare.
- “215” → This is the width of the tire in millimeters, measured from sidewall to sidewall. In this case, the tire is 215mm wide.
- “65” → Known as the aspect ratio. It’s the height of the sidewall as a percentage of the tire’s width. Here, the sidewall height is 65% of 215mm.
- “R” → Refers to the tire’s construction. “R” means radial, which is by far the most common type on modern vehicles.
- “15” → The diameter of the wheel (or rim) in inches that this tire will fit.
Why does this matter? Because putting the wrong size tire on your vehicle can mess with handling, fuel economy, and even your speedometer reading. That’s why at Burt Brothers, we always double-check your vehicle’s recommended size to make sure you get the perfect fit.
Understanding Load Index and Speed Rating
Beyond the size, you’ll also see a combination of numbers and letters, like 95H.
- Load Index (95) → This tells you how much weight each tire can safely support. A “95” load index equals 1,521 pounds. Multiply that by four tires, and you get the total safe load capacity for your car.
- Speed Rating (H) → This is the maximum sustained speed the tire can handle safely. For example, “H” means up to 130 mph, “V” means 149 mph, and “W” goes up to 168 mph.
Even if you never drive that fast, speed ratings matter because they also reflect how the tire handles heat and stress. In other words, a mismatched speed rating can mean less stability in everyday driving.
Decoding DOT Code and Tire Age
On every tire, you’ll see a longer code starting with DOT. This stands for the Department of Transportation and gives information about where and when the tire was manufactured.
The last four digits of the DOT code tell you the tire’s age. For example:
- 1223 → This tire was made in the 12th week of 2023.
Why does this matter? Because tires naturally degrade over time—even if you don’t drive much. Rubber hardens, cracks, and loses grip. Most experts (including us at Burt Brothers) recommend replacing tires that are 6–10 years old, regardless of tread depth.
Other Key Sidewall Markings to Know
- M+S (Mud and Snow) → Indicates that the tire is designed to handle light winter conditions.
- 3PMSF (Three-Peak Mountain Snowflake) → A stricter winter performance rating, showing the tire has passed tests for severe snow conditions.
- UTQG Ratings (Treadwear, Traction, Temperature) → These grades give you a snapshot of how long the tire should last, how well it grips on wet surfaces, and how resistant it is to heat.
- Max Inflation Pressure / Load → Not the same as your recommended tire pressure (that’s found in your vehicle’s manual or door placard), but the absolute maximum limit for that tire.
How Tire Specs Affect Driving Performance
Every spec on your sidewall has a direct impact on how your car performs.
- Tire size influences fuel efficiency, ride comfort, and handling.
- Load index ensures your vehicle can safely carry passengers and cargo.
- Speed rating affects cornering, stability, and safety at highway speeds.
- Seasonal markings make the difference between gripping the road in winter vs. sliding around.
Using the wrong specs can lead to uneven wear, reduced traction, and even dangerous blowouts. That’s why Burt Brothers technicians always match your tires to your driving needs—whether that’s commuting on I-15, heading to the ski slopes, or taking a road trip through the desert.
How to Choose the Right Tires Based on Sidewall Specs
Now that you know how to decode the markings, here’s how to use that knowledge:
- Check your vehicle’s tire placard (usually inside the driver’s side door) or owner’s manual for OEM specs.
- Use the sidewall info to compare tires when shopping online or in-store.
- Decide if you need a seasonal upgrade—like winter tires with the 3PMSF symbol.
- Consult with experts—if you’re unsure, bring your car to Burt Brothers, and we’ll walk you through the best options for your lifestyle and budget.
When to Inspect Your Tire Sidewalls
Even if your tread looks good, your sidewalls can tell you a lot about tire health. Look for:
- Cracks or dry rot
- Bulges or bubbles (often caused by potholes)
- Cuts or abrasions
Any of these signs can mean your tire’s structure is compromised—and it’s time to replace it. The safest move is to stop by Burt Brothers for a free inspection before hitting the road.
Know Your Tire Specs for a Safer, Smarter Drive
Your tire sidewall might look like a jumble of numbers and letters, but now you know it’s actually your roadmap to safer, smarter driving. From size and load rating to speed limits and seasonal performance, each marking tells you something vital about your tire’s capabilities.
By learning how to decode this information, you’ll be more confident in choosing the right tires, maintaining them properly, and knowing when it’s time for replacements.
At Burt Brothers Tire & Service, we believe informed drivers make safer drivers. So take a few minutes today, inspect your tire sidewalls, and if you have any questions, stop by one of our locations. Our team is always happy to help you decode your tires and keep your car running at its best.
Because at Burt Brothers, it’s not just about tires—it’s about keeping your family safe, your car reliable, and your journeys stress-free.
