How to Read Your Tire Sidewall Numbers (Complete Guide)

Every tire on your car has a series of numbers and letters molded into the sidewall. To most people, it looks like a secret code: P225/65R17 95H. But this sequence tells you everything you need to know about the tire — its size, what it's designed for, how fast it can safely go, how much weight it can carry, and even when it was manufactured.

Understanding these numbers matters for three practical reasons: buying the correct replacement tires, understanding your vehicle's capabilities, and knowing when your tires are too old regardless of tread depth. Let's decode every character.

The Primary Tire Size Code

The most prominent marking on any tire sidewall is the size code. Using P225/65R17 95H as our example, here's what each part means:

Tire Type Prefix: "P"

The letter before the numbers indicates the tire's intended use:

• P — Passenger vehicle. This is the most common prefix on cars, crossovers, and light SUVs.
• LT — Light Truck. Designed for heavier vehicles like full-size trucks and SUVs. These have stronger sidewalls and higher load capacities.
• ST — Special Trailer. Made exclusively for trailers — never for driven axles.
• No prefix — Euro-metric sizing. Functionally similar to P-metric but follows European standards. Common on European vehicles.

The prefix matters when replacing tires. Putting P-rated tires on a truck that calls for LT tires is dangerous — they can't handle the load.

Section Width: "225"

This is the tire's width in millimeters, measured from sidewall to sidewall when properly mounted and inflated. A 225 tire is 225mm (about 8.9 inches) wide. Wider tires generally provide more grip but may reduce fuel economy and increase road noise. Your vehicle was designed for a specific width — stick with it unless you know what you're doing.

Aspect Ratio: "65"

This is the height of the sidewall expressed as a percentage of the width. A 65 aspect ratio means the sidewall height is 65% of 225mm, which equals approximately 146mm. Lower numbers mean shorter sidewalls (sportier handling, harsher ride). Higher numbers mean taller sidewalls (more comfortable, more flex).

• 40-50: Low-profile, sporty. Common on performance cars.
• 55-65: Mid-range. Good balance of comfort and handling. Most sedans and crossovers.
• 70-80: Tall sidewall. Comfortable ride, good for trucks and SUVs. More puncture resistant.

Construction Type: "R"

The letter after the aspect ratio indicates internal construction:

• R — Radial. Virtually all modern passenger tires are radial. The internal cord plies run perpendicular to the direction of travel, providing flexibility and better heat dissipation.
• D — Diagonal (bias-ply). Older technology, still used on some trailers and specialty applications.
• B — Belted. Rare. A hybrid of radial and bias construction.

Wheel Diameter: "17"

The rim size this tire fits, measured in inches. This must match your wheel exactly — a 17-inch tire only fits a 17-inch wheel. Common passenger car sizes range from 14 to 22 inches, with 16-18 being the most common for everyday vehicles.

Load Index: "95"

This number corresponds to the maximum weight each tire can support when properly inflated. It's not the actual weight in pounds — it's an index that maps to a weight chart:

• 85: 1,135 lbs per tire
• 90: 1,323 lbs per tire
• 95: 1,521 lbs per tire
• 100: 1,764 lbs per tire
• 105: 2,039 lbs per tire
• 110: 2,337 lbs per tire

Never install tires with a lower load index than what your vehicle requires. You can find the required load index on the tire placard inside the driver's door jamb.

Speed Rating: "H"

The maximum speed the tire is engineered to sustain safely. Common ratings:

• S: 112 mph
• T: 118 mph
• H: 130 mph
• V: 149 mph
• W: 168 mph
• Y: 186 mph

In practice, you'll never reach these speeds legally. But the speed rating also reflects the tire's heat resistance and handling characteristics at all speeds. Higher-rated tires generally handle better but may wear faster and ride more firmly.

The DOT Date Code: How Old Are Your Tires?

This is the most overlooked and potentially the most important marking on your tire. On one sidewall, you'll find a DOT (Department of Transportation) code that ends with four digits. These four digits are the manufacturing date.

For example: DOT XXXX XXXX 2319

The last four digits — 2319 — mean the tire was manufactured in the 23rd week of 2019.

Why does this matter? Rubber degrades over time, regardless of use. The oils and chemicals that keep the rubber flexible slowly evaporate. Industry experts and most manufacturers recommend replacing tires that are 6 years old from the date of manufacture, regardless of remaining tread depth. At 10 years, tires should be replaced unconditionally.

This is especially important when buying used tires or when tires have been sitting in a shop's inventory. A "new" tire that was manufactured 4 years ago only has 2 years of safe service life remaining.

UTQG Ratings: Treadwear, Traction, and Temperature

The Uniform Tire Quality Grading (UTQG) system, required by the U.S. government, provides three ratings:

Treadwear Rating

A comparative number indicating how long the tread should last relative to a reference tire. A tire rated 400 should last twice as long as one rated 200, under the same conditions. Most passenger tires range from 200 to 800. These numbers are assigned by the manufacturer and can be somewhat optimistic.

Traction Rating

Measures the tire's ability to stop on wet pavement in a straight line. Grades from best to worst: AA, A, B, C. Most quality passenger tires are rated A or AA. Avoid C-rated tires if you drive in rain.

Temperature Rating

Indicates the tire's resistance to heat buildup. Grades: A, B, C. All tires sold in the U.S. must meet at least a C rating. Higher-speed-rated tires generally have higher temperature ratings because they're engineered to manage heat at sustained high speeds.

Other Sidewall Markings

M+S or M/S

Stands for "Mud and Snow." Indicates the tread pattern is designed for some off-road and winter capability. This is a self-declared rating by the manufacturer and doesn't require testing. Most all-season tires carry this marking.

Three-Peak Mountain Snowflake (3PMSF)

A more rigorous winter capability rating that requires actual testing. Tires with this symbol provide significantly better snow traction than M+S-only tires. If you drive in real winter conditions, look for this symbol.

Max Pressure

Stamped on the sidewall as "Max Press XX PSI." This is the maximum pressure the tire can safely hold — not the recommended inflation pressure for your vehicle. Your correct pressure is on the placard in the driver's door jamb. Over-inflating to the max pressure on the sidewall will give you a harsh ride and uneven center wear.

Directional and Asymmetric Indicators

Some tires have specific mounting requirements:

• "Rotation" with an arrow: Directional tires must be mounted so they rotate in the indicated direction.
• "Outside" marking: Asymmetric tires have different tread patterns on each side and must be mounted with the correct side facing out.

Practical Applications

Buying Replacement Tires

Match the size code on your current tires (or the tire placard on your door jamb) exactly. Same width, aspect ratio, construction type, and wheel diameter. You can go up or down slightly on load index and speed rating, but never below the vehicle manufacturer's specification.

Checking Tire Age Before Purchase

Always check the DOT date code on any tire before buying — especially from warehouse stores or online sellers. If the tire is already 2+ years old, negotiate a discount or choose a fresher set.

Identifying Mixed Tires

After buying a used car, check all four tires. Ideally, they should be the same brand, model, and size. Mixed tires can affect handling, especially in emergency maneuvers. At minimum, ensure both tires on each axle match.

Your vehicle's complete tire specifications are part of the data we store when you add your car to Your Service Book. We track tire age alongside your maintenance schedule so you know when it's time for replacement — even if the tread looks fine.