How to Read Tire Sizes: Complete Guide for Beginners

Ever looked at the side of your tire and seen something like P275/55R20 and wondered what it means? You're not alone. Understanding tire sizes is essential for buying the right tires for your vehicle.

Breaking Down the Tire Size Code

Let's use P275/55R20 as our example:

P = Tire Type

• P = Passenger vehicle tire
• LT = Light Truck tire (heavier duty)
• ST = Special Trailer tire
• No letter = European metric tire

275 = Width in Millimeters

This is the width of the tire from sidewall to sidewall when mounted. 275mm equals about 10.8 inches.

Common widths:

• 205-225mm = Compact cars
• 235-265mm = Sedans and crossovers
• 275-305mm = Trucks and SUVs
• 315-355mm = Performance cars and lifted trucks

55 = Aspect Ratio

This is the sidewall height as a percentage of the width. A 55 aspect ratio means the sidewall is 55% as tall as the tire is wide.

• Lower number (30-45) = Shorter sidewall, sportier look, stiffer ride
• Higher number (55-75) = Taller sidewall, more comfortable, better off-road

R = Construction Type

• R = Radial (99% of modern tires)
• B = Bias-ply (rare, specialty use)
• D = Diagonal (very rare)

20 = Wheel Diameter in Inches

This tells you what size wheel the tire fits. A 20 means it fits a 20-inch wheel.

Additional Tire Markings

Load Index

Usually appears after the diameter (e.g., P275/55R20 113). The load index tells you how much weight each tire can support.

| Load Index | Max Load (lbs) | |------------|----------------| | 100 | 1,764 | | 105 | 2,028 | | 110 | 2,337 | | 115 | 2,679 | | 120 | 3,086 |

Speed Rating

A letter after the load index (e.g., P275/55R20 113H). This indicates the maximum speed the tire is rated for.

| Rating | Max Speed | |--------|-----------| | S | 112 mph | | T | 118 mph | | H | 130 mph | | V | 149 mph | | W | 168 mph | | Y | 186 mph |

Common Tire Size Questions

Can I Use a Different Tire Size?

Yes, but be careful. You can usually go slightly wider or taller, but:

• Stay within 3% of original diameter to avoid speedometer errors
• Check for fender clearance
• Maintain similar load capacity

What's the Difference Between P and LT Tires?

P-metric tires are designed for passenger vehicles and prioritize comfort and fuel efficiency.

LT tires are built tougher for trucks and heavy loads. They have:

• Stronger sidewalls
• Higher load capacity
• Better puncture resistance
• Slightly rougher ride

How Do I Find My Original Tire Size?

Check these locations:

1. Driver's door jamb - Look for a sticker with tire info
2. Owner's manual - Lists recommended sizes
3. Current tires - If they're original equipment

Example Tire Sizes by Vehicle Type

Compact Cars

• Toyota Corolla: 205/55R16
• Honda Civic: 215/55R17

Midsize Sedans

• Toyota Camry: 235/45R18
• Honda Accord: 235/40R19

Trucks

• Ford F-150: 275/55R20
• Chevy Silverado: 275/60R20
• RAM 1500: 275/55R20

SUVs

• Toyota 4Runner: 265/70R17
• Jeep Wrangler: 255/70R18
• Ford Bronco: 285/70R17

Find Your Perfect Tires

Now that you understand tire sizes, finding the right tires is easy. At Warehouse Tire Direct, simply:

1. Enter your year, make, and model
2. Select your trim level
3. Browse tires guaranteed to fit

All our tires are fitment-verified, so you'll never get the wrong size.

Shop Tires for Your Vehicle →