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Tire Sidewall Decoder

How to Read a Tire Size Code

Learn what every number, letter, and safety symbol on your tire's sidewall actually means.

Sidewall Markings Breakdown & Meaning

Example Tire Sidewall Stamp
P225/55R17 97V
Technical blueprint diagram of tire sidewall anatomy showing section width in millimeters, sidewall height calculation, rim diameter in inches, and radial bead construction
Engineering HUD Blueprint
Tire Cross-Section Anatomy: Visualizing section width (305 mm), sidewall aspect height (30% = 91.5 mm), and wheel diameter (21").
ISO 4000-1 Metric Standard
P225 — Type & Section Width

P indicates Passenger car tire (LT = Light Truck, ST = Special Trailer). 225 is cross-section width in millimeters.

225 mm (8.86")
55 — Aspect Ratio (Profile)

Sidewall height is 55% of the tire's 225 mm section width (123.75 mm / 4.87 inches).

55% of Width
R — Internal Construction

Radial construction: internal cord plies run perpendicular at 90 degrees to the direction of travel.

Radial Ply
17 — Wheel Rim Diameter

Diameter of the metal wheel rim in inches that this tire is manufactured to mount onto.

17" Wheel
97 — Load Index

Numerical code representing maximum load capacity at proper cold tire pressure (97 = 1,609 lbs / 730 kg per tire).

1,609 lbs
V — Speed Rating

Maximum safe sustained highway velocity capability of the tire under full rated load.

149 mph (240 km/h)

Official Tire Speed Rating Chart

Rating Top Speed Limit Typical Vehicle Application
Q 99 mph (160 km/h) Winter & Off-Road Tires
R 106 mph (170 km/h) Heavy Duty Light Trucks
S 112 mph (180 km/h) Family Vans & SUVs
T 118 mph (190 km/h) Standard Sedans
H 130 mph (210 km/h) Sport Sedans & Coupes
V 149 mph (240 km/h) Performance Vehicles
W 168 mph (270 km/h) High-Performance Sports Cars
Y 186 mph (300 km/h) Exotic & Supercars
(Y) 186+ mph (300+ km/h) Ultra High-Performance Tracks

How to Find Tire Age: The DOT Date Stamp SAFETY ESSENTIAL

Every tire manufactured after 2000 has a 4-digit date code at the end of its DOT serial number (e.g. DOT XXXX 4223).

First 2 Digits (42): Week 42 (Mid-October)
Last 2 Digits (23): Year 2023

Tire manufacturers recommend replacing tires after 6 to 10 years regardless of remaining tread depth due to rubber oxidation and dry rot.

Frequently Asked Questions About Tire Sidewall Markings

What does the letter R stand for in a tire size?
The letter 'R' indicates Radial ply construction. Over 98% of modern vehicle tires are radials, meaning internal polyester and steel cord plies run perpendicular (at 90 degrees) to the direction of travel, delivering superior tread life, ride comfort, and fuel efficiency compared to bias-ply tires.
What do the P and LT prefixes mean?
'P' indicates P-Metric (passenger vehicles like sedans, minivans, and small crossovers). 'LT' indicates Light Truck (constructed with heavier plies for 1/2-ton, 3/4-ton, and 1-ton trucks carrying heavy cargo or towing trailers). If no letter precedes the width, it follows European (Euro-Metric) sizing standards.
How do you find out how old a tire is using the DOT code?
Look at the outer sidewall for the DOT serial number and check the final 4 enclosed digits (e.g. 2423). The first two digits represent the week of manufacture (Week 24 = June), and the last two digits represent the calendar year (2023). Regardless of tread depth, tires should be inspected or replaced once they reach 6 to 10 years of age due to dry rot.
Can I install tires with a lower speed rating than OEM?
Automakers and tire manufacturers strongly recommend never downgrading speed ratings below the vehicle's factory door placard specification. Fitting lower-rated tires can compromise emergency high-speed lane changes, alter anti-lock braking (ABS) calibration, and potentially void auto insurance liability coverage.