ENCYCLOPEDIA OF TIRE
SIDEWALL MARKINGS & SPECS
The definitive technical authority on passenger, performance, and racing tire sidewall markings. Decodes UTQG ratings, speed ratings, load index tables, OEM factory homologations, severe winter certifications, and extended mobility run-flat technologies under NHTSA and ETRTO standards.
UTQG (UNIFORM TIRE QUALITY GRADING)
Mandated by the U.S. National Highway Traffic Safety Administration (NHTSA) for passenger tires (excluding winter and deep-tread truck tires), UTQG evaluates relative tread life, wet straight-line braking coefficient, and high-speed thermal dissipation.
A comparative numerical index based on wear results over a 7,200-mile government test course in San Angelo, Texas. A tire rated 400 will wear twice as long on the test track as a baseline tire rated 200. High-performance track tires often carry 100-200 ratings, while touring tires reach 600-800.
Evaluates straight-line wet stopping capability on skid pads at 40 mph over wet asphalt and wet concrete. AA is the absolute highest rating reserved for extreme wet grip performance, followed by A, B, and C (lowest). Note: UTQG traction does NOT measure wet cornering grip.
Measures the tire’s resistance to heat generation and its ability to dissipate thermal buildup during sustained indoor high-speed test wheel runs. Rating A withstands speeds over 115 mph, B between 100–115 mph, and C meets minimum federal safety requirement (85–100 mph).
SPEED RATING SYMBOLS & MAXIMUM VELOCITY CHART
The speed rating symbol is an alphabetical code indicating the maximum certified speed at which a tire can carry a load corresponding to its Load Index under specified laboratory conditions.
| Speed Symbol | Max Certified Speed (MPH) | Max Certified Speed (KM/H) | Typical Vehicle Category |
|---|---|---|---|
| L | 75 mph | 120 km/h | Off-Road & Heavy Commercial Light Truck |
| M | 81 mph | 130 km/h | Special Temporary Spare Tires |
| Q | 99 mph | 160 km/h | Studded Winter & Heavy 4x4 Off-Road Tires |
| R | 106 mph | 170 km/h | Heavy Duty Light Truck & Van Tires |
| S | 112 mph | 180 km/h | Standard Passenger Cars & Family Sedans |
| T | 118 mph | 190 km/h | Family Passenger Cars & Crossovers |
| H | 130 mph | 210 km/h | Sport Sedans, Coupes & Mid-size SUVs |
| V | 149 mph | 240 km/h | High Performance Sedans & Sports Cars |
| W | 168 mph | 270 km/h | Ultra High Performance (UHP) GT Cars |
| Y | 186 mph | 300 km/h | Supercars & Exotic High Speed Sports Cars |
| (Y) | > 186 mph | > 300 km/h | Hypercars (Tested individually above 186 mph) |
| ZR | > 149 mph | > 240 km/h | High Speed Designation embedded in Size Rating (e.g. 245/40ZR18) |
FACTORY VEHICLE MANUFACTURER APPROVAL MARKS
Leading luxury and sports car manufacturers collaborate with tire makers to engineer custom compound blends, casing stiffness, and tread patterns specifically tuned for their suspension geometry. These original equipment (OE) tires carry specialized homologation stamps on the sidewall.
MO = Original Equipment, MOE = Extended Mobility (Run-Flat), MO1 = AMG High Performance.
Factory star mark indicating custom compound tuning for BMW xDrive and rear-wheel dynamics.
AO = Audi Original, RO1 & RO2 = Audi Sport RS performance model homologations.
Sequential revision series (N0 to N4) mandatory for Porsche 911, Cayman, and Taycan warranty specs.
Custom compound and casing structure designed for Ferrari mid-engine and V12 supercars.
Tesla homologation featuring low rolling resistance and internal acoustic foam for noise reduction.
General Motors Tire Performance Criteria number ensuring strict handling and treadwear standards.
Bespoke compound certification for Aston Martin GT models and DB Series sports cars.
3PMSF SNOWFLAKE VS M+S SYMBOLS
The 3PMSF symbol (a snowflake inside a mountain with three peaks) is the official regulatory standard proving a tire has passed objective, standardized acceleration tests on packed snow under ASTM F1805 standards. It guarantees a minimum 10% traction improvement over standard M+S reference tires. Required by law in winter-zone mountain passes across North America and Europe.
The M+S (or M&S, MS) marking indicates that a tire’s tread geometry has a minimum 25% open tread ratio designed to pack and evacuate loose mud or light snow. Unlike 3PMSF, M+S is a self-certified geometric rating that does NOT require laboratory snow traction testing. Most all-season tires carry M+S, but they harden in severe cold below 45°F (7°C).
RUN-FLAT & SELF-SEAL BRAND CODES
Run-flat tires feature reinforced self-supporting sidewalls or internal support rings that allow continued driving up to 50 miles (80 km) at 50 mph (80 km/h) following a complete loss of air pressure.