Those numbers and letters on your tire sidewall might look like a complex code at first glance. But here’s the thing – they tell you everything about your tires’ capabilities.
Your tire markings pack crucial details about speed ratings (from 3 mph to 186+ mph), load capacity, and safety features. Most drivers overlook these vital specifications, though they’re easily visible on your door jamb and gas tank hatch.
The right tire size means more than just proper fitment. Your safety depends on choosing tires with appropriate traction (AA to C ratings) and temperature resistance (A to C grades). These ratings directly affect how your vehicle handles on the road.
Want to read tire sizes like a pro? Let’s walk through these markings step by step. You’ll learn exactly what to look for when choosing the perfect tires for your vehicle.
Table of Contents
5 Places to Find Your Tire Size: Quick Location Guide
Need to check your tire size? Car manufacturers make this information easy to spot throughout your vehicle. Here’s your complete guide to finding the right specifications without any special tools.
Tire Sidewall
Your tire’s sidewall offers the most straightforward source for size information. Look for number-letter combinations like “P225/55R17” or “215/55Z R17” prominently displayed on the outer and inner walls. These codes pack essential details about width, aspect ratio, and wheel diameter. While the markings might seem puzzling at first, they become second nature with practice. Pro tip: Check all four tires – some vehicles use different sizes for front and rear wheels.
Driver’s Door Jamb
The driver’s side door jamb serves as your go-to spot for tire specifications. Here you’ll find a manufacturer-installed sticker showing recommended tire sizes and inflation pressures. This information proves especially valuable since it reflects your vehicle’s original specifications.
Owner’s Manual
Your vehicle’s manual packs everything you need to know about tire specifications. Flip through the dedicated wheels and tires section for detailed size recommendations, pressure guidelines, and even approved alternative tire sizes. The index makes finding this information quick and simple.
Fuel Door
Pop open your fuel door to spot another helpful reference point. Many manufacturers tuck a small sticker here displaying the original equipment tire size. This location proves particularly handy during exterior vehicle checks.
Glove Box
Check inside your glove compartment door for a tire information decal. These stickers feature easy-to-read graphics showing proper tire sizes and pressure levels. Classic car owners take note – many vintage vehicles came standard with these helpful glove box references.
Remember to cross-check these locations, especially if your vehicle runs on replacement tires different from the original set.
If you ever wondered how to read tires. pic.twitter.com/DGJLsgGKXW
— World of Engineering (@engineers_feed) March 18, 2025
Tire Size Explained – Basic Tire Size Markings: Your Essential Guide
Here’s what those numbers and letters on your tire sidewall really mean. Each marking plays a crucial role in your tire’s performance and safety specs.
Tire Type Letters: P, LT, ST
Your tire’s first letter tells you exactly what type of vehicle it’s built for:
- P (Passenger): Made for cars, minivans, SUVs, and light pickup trucks
- LT (Light Truck): Built tough for heavy loads and trailer towing
- ST (Special Trailer): Specifically designed for trailer use, from boat haulers to utility trailers
- T (Temporary): Your spare tire, with limited speed and distance ratings
No letter up front? You’re looking at a European metric tire – these pack different load ratings than P-metric options.
Width Numbers: Millimeter Measurements
Next comes a three-digit number showing your tire’s width. Take “P225/60R16” – that “225” means your tire measures 225 millimeters across at its widest point.
Aspect Ratio: Height vs Width
The number after the slash tells you about sidewall height. A 225/60 tire’s sidewall reaches 60% of its width (225mm × 0.60 = 135mm).
Taller sidewalls (higher numbers) give you:
- Smoother rides with better shock absorption
- Extra rim protection
- Tougher performance on rough roads
Shorter sidewalls (lower numbers) deliver:
- Sharper handling response
- Better cornering grip
- That sporty look you might want
Construction Code: R Means Radial
That “R” in your tire size? It stands for radial construction, with internal cords running at 90-degree angles. Radial tires beat older designs by offering:
- Better fuel economy through lower resistance
- Stronger road grip
- Longer-lasting comfort
Watch for less common codes like “B” (bias belted) or “D” (diagonal bias-ply) on specialty tires.
Rim Diameter and Fitment: The Perfect Match
Those last numbers in your tire size code make all the difference. Wheel diameter demands exact matching – there’s no wiggle room here.
Wheel Diameter Numbers
Look at the final digits in your tire size (P225/70R16 91S) – that’s your wheel diameter in inches. This number shows the distance across your wheel between bead seats. Here’s the golden rule: 16-inch tires fit only 16-inch wheels. No stretching, no compromising.
Perfect Tire-to-Wheel Matching
Diameter matches? Great. Now let’s talk width compatibility. Your tire width must match your rim’s recommended range. Take a 6-inch rim – it needs tires between 175mm and 205mm wide, with sweet spots at 185mm or 195mm.
Swapping wheels? Check these crucial points:
- Bolt pattern: Count studs and measure their spacing
- Hub size: Your wheel’s center bore must match vehicle specs
- Offset: Watch that mounting surface position
Car makers pick wheels that perfectly match your vehicle’s suspension, gearing, and body design. Straying too far from these specs puts your ride quality at risk.
Size Mistakes That Cost You
Wrong tire size tops the list of buying blunders. Poor sizing wrecks handling and burns extra fuel. Many drivers fall for a dangerous myth – thinking any tire that slides onto a wheel works fine.
Watch out for these common traps:
- Mounting tires too wide or narrow for your rims – hello, premature wear and safety risks
- Picking wrong load ratings for your vehicle’s weight
- Skipping speed rating checks on replacement tires
- Choosing oversized tires for looks without checking clearance
Remember: proper fitment keeps tires from rubbing against wheel wells or suspension parts. That’s not just about comfort – it’s about keeping you safe on the road.
Performance Ratings: What Your Tire Numbers Really Mean
Want to know if your tires can handle your driving needs? Performance ratings tell you exactly what your tires can do. Here’s your guide to reading these crucial safety markers.
Load Index: Your Tire’s Strength Score
Check that two-digit number after your tire size (P225/60R16 91V) – it’s your load index. A 91 rating means each tire handles up to 615 kg (1,356 pounds). Most passenger cars need ratings between 75 and 100 – higher numbers mean stronger tires.
Light truck owners, watch for double numbers like 120/116 . These show weight limits for single and dual tire setups. Never pick tires with lower load ratings than your vehicle needs – that’s asking for trouble and early tire failure.
Speed Ratings: The Letter That Matters
That last letter in your tire code (P225/60R16 91V) packs crucial speed info. These ratings run from L (75 mph) all the way to Y (186 mph).
Here’s a quirky fact: The “H” rating jumps between U and V, originally meaning “high performance” at 130 mph. Remember though – these ratings show what’s possible in perfect conditions, not your green light to speed.
UTQG Ratings: The Government’s Grade
The Department of Transportation created these ratings to help you compare tires:
- Treadwear: Numbers from 100-1000 show longevity. A 400 tire should last twice as long as a 200
- Traction: Grades AA to C tell you about wet braking power
- Temperature: A, B, or C grades show heat resistance. “A” means the tire handles 115+ mph
Pressure Limits: The Numbers That Keep You Safe
See that “MAX PRESS” on your sidewall? That’s not your target pressure. Always check your door jamb or manual for the right numbers.
Getting pressure right matters big time. Just 10% too low cuts fuel economy by 1% and slashes tire life by 25%. Plus, proper inflation keeps you safe with better handling and no surprise blowouts.
The Bottom Line: Your Tire Knowledge Toolkit
Those tire markings aren’t just random numbers anymore, right? Each code tells you exactly what your tires can handle – from heavy loads to high speeds.
Smart tire shopping starts with these specs. Match them perfectly to your vehicle, and you’ll get the handling, fuel savings, and safety you need. Plus, now you know exactly where to find this info – whether you’re checking the sidewall, door jamb, or flipping through your manual.
Here’s what matters most: tire specs pack more punch than just size. Load indexes keep you safe with heavy cargo. Speed ratings match your driving needs. UTQG grades tell you about durability. Put them all together, and you’ve got the complete picture.
Ready to shop for tires? You’ve got all the knowledge you need right here. Keep these specs handy, check your pressure regularly, and your tires will deliver the performance and safety you’re looking for.
Read more:
- Best Car to Buy According to your Monthly Salary in 2025
- How to Jump Start a Car Safely? The Emergency Guide for Beginners
FAQs
How do you correctly read a tire size?Â
To read a tire size, start with the width in millimeters, followed by the aspect ratio, then the construction type (usually R for radial), and finally the wheel diameter in inches. For example, 225/60R16 would be read as “225, 60, R, 16.”
What do the letters and numbers in a tire size mean?
The letters and numbers in a tire size provide important information. For instance, in P225/60R16 91H, “P” indicates a passenger vehicle tire, “225” is the width in millimeters, “60” is the aspect ratio, “R” means radial construction, “16” is the wheel diameter in inches, “91” is the load index, and “H” is the speed rating.
Where can I find my vehicle’s recommended tire size?
You can find your vehicle’s recommended tire size in several locations, including the driver’s side door jamb, inside the fuel door, in the vehicle owner’s manual, on a sticker in the glove compartment, or on the sidewall of your current tires.
What is the importance of the load index and speed rating on a tire?
The load index indicates the maximum weight a tire can support when properly inflated, while the speed rating represents the maximum speed a tire can safely maintain. These ratings are crucial for ensuring your tires can handle your vehicle’s weight and intended use safely.
How does tire size affect vehicle performance?
Tire size can significantly impact vehicle performance. Wider tires generally provide better traction and handling, while taller sidewalls (higher aspect ratio) often offer improved ride comfort. However, changing tire size from the manufacturer’s recommendations can affect speedometer accuracy, fuel efficiency, and overall driving dynamics.
