When it comes to vehicles, tires are one of the most critical components. They directly affect your car’s handling, safety, fuel economy, and comfort. Yet, for many drivers, the numbers and letters printed on the sidewall of a tire look like a confusing code. That’s where a tire size chart comes in handy.
A tire size chart helps you decode these numbers, understand what they mean, and select the right tires for your vehicle. Whether you are replacing worn-out tires, upgrading to performance tires, or simply trying to understand your vehicle better, knowing how to read a tire size chart will save you money, time, and stress.
In this guide, we will break down everything you need to know about tire sizes, explore how to read them, and provide a clear tire size chart for easy reference.
Why Tire Size Matters
The size of your tires influences nearly every aspect of your driving experience:
Safety: Correct tire size ensures proper traction, braking, and handling.
Fuel efficiency: Larger or smaller tires than recommended can reduce fuel economy.
Comfort: The wrong size tire may cause vibrations or rough rides.
Performance: Proper tire size maintains speedometer accuracy and vehicle balance.
Using the wrong size tire is more than just an inconvenience—it can lead to faster wear, suspension issues, or even accidents. That’s why car manufacturers specify exact tire sizes for every model.
How to Read Tire Sizes
If you look at the sidewall of your tire, you’ll see a series of numbers and letters like this:
Example: P215/65R15 95H
Here’s how to decode it:
Tire Type (P, LT, or no letter):
P = Passenger vehicle
LT = Light truck
If there’s no letter, it’s a European tire standard.
Tire Width (215):
The width of the tire in millimeters from sidewall to sidewall.
Example: 215 mm wide.
Aspect Ratio (65):
The height of the sidewall as a percentage of the width.
65 means the height is 65% of the tire’s width.
Construction Type (R):
R = Radial (most common today).
D = Diagonal or bias ply.
B = Belted bias.
Rim Diameter (15):
The diameter of the wheel rim in inches.
Example: Fits a 15-inch rim.
Load Index (95):
A numerical code showing the maximum weight the tire can carry.
95 means the tire can carry 1,521 lbs.
Speed Rating (H):
A letter that shows the maximum safe speed for the tire.
H = up to 130 mph.
Tire Size Chart (Quick Reference)
Below is a simplified tire size chart to help you understand the common sizes and what they mean.
| Tire Size Example | Tire Width (mm) | Aspect Ratio | Rim Diameter (in) | Load Index | Speed Rating |
|---|---|---|---|---|---|
| P195/65R15 89H | 195 | 65 | 15 | 89 (1279 lbs) | H (130 mph) |
| P205/55R16 91V | 205 | 55 | 16 | 91 (1356 lbs) | V (149 mph) |
| P215/60R17 96T | 215 | 60 | 17 | 96 (1565 lbs) | T (118 mph) |
| LT245/75R16 120R | 245 | 75 | 16 | 120 (3086 lbs) | R (106 mph) |
| P225/40R18 92W | 225 | 40 | 18 | 92 (1389 lbs) | W (168 mph) |
Tire Size Conversion: Metric vs. Standard
Some drivers still refer to tire sizes in inches instead of the metric system. For example, instead of 265/70R17, you may hear “31-inch tires.”
Here’s a quick formula to convert metric sizes into inches:
Convert tire width from millimeters to inches: (1 inch = 25.4 mm)
Multiply width by aspect ratio to find sidewall height.
Double the sidewall height and add rim diameter: That gives the overall diameter.
Example: 265/70R17
Width = 265 mm ÷ 25.4 = 10.43 in
Sidewall height = 265 × 0.70 = 185.5 mm (7.3 in)
Overall diameter = 7.3 × 2 + 17 = 31.6 inches
So, 265/70R17 ≈ 31.6-inch tires.
Choosing the Right Tire Size for Your Vehicle
Here are some key tips when using a tire size chart to pick tires:
Check the Owner’s Manual or Door Sticker
Most vehicles have a placard inside the driver’s side door frame listing the recommended tire size.
Stay Close to OEM Specifications
You can switch to slightly wider or narrower tires, but don’t deviate too much from the manufacturer’s recommendation.
Consider Your Driving Conditions
Off-road vehicles often use larger tires for ground clearance.
City driving may favor smaller, more fuel-efficient tires.
Mind the Load and Speed Ratings
Always match or exceed the factory ratings for safety.
Check Rim Compatibility
A tire must fit the rim width properly. Using mismatched tires and rims can be dangerous.
Common Tire Size Categories
Passenger Car Tires (P-metric):
Example: P195/65R15
Found on sedans, hatchbacks, and compact cars.
Light Truck Tires (LT-metric):
Example: LT265/70R17
Stronger sidewalls for SUVs, trucks, and towing vehicles.
Temporary Spare Tires (“Donut” tires):
Smaller and narrower, designed only for short-term use.
Performance Tires:
Low-profile with larger rims for high-speed handling.
Example: P225/40R18.
Off-Road Tires:
Larger diameters and aggressive treads for rough terrain.
Impact of Changing Tire Size
Many drivers wonder if they can upsize or downsize their tires. While it’s possible, you need to consider the consequences:
Upsizing (larger tires):
Improves ground clearance and aggressive look.
May reduce fuel efficiency and affect speedometer accuracy.
Downsizing (smaller tires):
Can improve comfort and fuel economy.
May reduce handling and performance.
Always consult a tire size chart or a professional before changing tire sizes.
Tire Size and Speedometer Accuracy
Your speedometer is calibrated based on the factory-installed tire size. If you install larger tires, your vehicle will actually travel faster than your speedometer shows. With smaller tires, the opposite happens.
For example:
Factory tire: 205/55R16 → Speedometer accurate.
Larger tire: 225/55R16 → Speedometer may read 60 mph, but you’re actually going 62 mph.
This may not seem like much, but over time it affects mileage tracking, cruise control, and fuel economy calculations.
Common Mistakes Drivers Make with Tire Sizes
Even with charts and guides, many drivers still make costly mistakes when choosing tires. Here are the most common ones:
Mixing Different Sizes on One Vehicle
Some drivers install different tire sizes on the front and rear axles without realizing the risk. Unless your vehicle is specifically designed for staggered setups (like some sports cars), this can lead to poor handling, uneven wear, and drivetrain stress.
Ignoring Load Index and Speed Rating
Many focus only on width and diameter, forgetting that the load index and speed rating are just as important. A tire with a lower load rating may not safely carry the vehicle’s weight, especially when fully loaded.
Choosing Tires for Looks, Not Function
Bigger tires may look sporty, but they can hurt fuel economy, alter suspension dynamics, and make rides less comfortable. Always balance style with safety and practicality.
Tips for Tire Maintenance and Longevity
Once you’ve chosen the right size using a tire size chart, proper care will ensure they last longer:
Check Tire Pressure Regularly: Underinflated or overinflated tires wear unevenly and reduce fuel efficiency.
Rotate Tires Every 5,000–7,000 Miles: This prevents uneven wear across all four tires.
Balance and Align Wheels: Misaligned wheels can wear tires prematurely and affect handling.
Inspect for Damage: Look for cracks, bulges, or punctures that can compromise safety.
The Bottom Line
A tire size chart is your roadmap to safe and smart tire choices. By understanding tire codes, avoiding common mistakes, and maintaining your tires properly, you’ll get the best performance, safety, and lifespan out of them.
Final Thoughts
A tire size chart is more than just a table of numbers—it’s a guide that helps you keep your vehicle safe, efficient, and reliable. By learning how to read tire sizes, you can confidently choose the right tires for your car, truck, or SUV.
Next time you see a code like P215/65R15, you’ll know exactly what it means, how it affects your ride, and whether it’s the right fit for your vehicle.
Whether you stick with your manufacturer’s recommendation or explore different options, always use a tire size chart to guide your decision. Your safety, comfort, and wallet will thank you.
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