UN GTR No.16: Global Tire Technical Regulations Explained

Understanding UN GTR No.16: Global Technical Regulations for Tires

UN Global Technical Regulation No.16 (UN GTR No.16) establishes unified performance requirements for new pneumatic radial tires used on vehicles with gross mass up to 4,536 kg (10,000 lbs). This guide summarizes the regulation’s scope, test methods, key thresholds, and the history of its amendments.

Keywords: UN GTR 16; tire regulation; tire testing; rolling resistance; wet grip; tire noise; endurance test; bead unseating

Regulation Background

UN GTR No.16 was developed under the 1998 UN Agreement, harmonizing tire requirements drawn primarily from four core documents: UN R30, UN R54, UN R117, and US FMVSS 139. Before harmonization, tire makers produced nearly identical tires but had to make region-specific changes for different markets — particularly sidewall markings — driving up costs. The regulation aims to enable a “global tire” that meets all major markets with one product.

Development History

• 2004: Informal work began in Paris; France led the proposal.
• 2006: AC.3 formally approved the project at WP.29 session 140.
• 2009: AC.3 approved a two-phase approach: Phase 1 for passenger car tires, Phase 2 for LT/C (light truck/commercial) tires.
• Original GTR-16: Harmonized passenger car tire requirements; LT/C provisions from existing UN/US regulations were included as non-harmonized placeholders.
• Amendment 1 (2016): Updated wet grip to latest R117; added rolling resistance and severe-snow tire grading tests.
• Amendment 2: Harmonized LT/C tire physical dimensions and high-speed performance tests, incorporating latest R30, R54, and FMVSS updates.

Key harmonized areas: high-speed performance, physical dimensions, mandatory sidewall markings. Tests that existed in only one regulation (endurance, low-pressure endurance, bead unseating, strength, rolling noise, wet grip, run-flat) were adopted directly without reconciliation.

Scope

Applies to new pneumatic radial tires for Category 1 and 2 vehicles (gross mass ≤4,536 kg). Does not apply to:

• T-type temporary spare tires
• Rim diameter code ≤8 (≤203 mm)
• ST special trailer tires
• LT/C tires with tread depth ≥14.3 mm (18/32″)
• C3 category tires (except load index 122–131 with LT/C designation)

Sidewall Markings

The Tire Identification Number (TIN) follows format YYY-MMMMMM-DDDD:

• YYY: 3-digit global plant code (assigned by NHTSA)
• MMMMMM: 6-digit manufacturer code (internal)
• DDDD: 4-digit date code (2 digits week + 2 digits year, e.g., 0110 = week 1 of 2010)

Required markings include: manufacturer/trademark (≥4 mm), commercial name, country of origin, size designation (≥6 mm), R (radial) or RF (run-flat radial), service description, max load/pressure, M+S or alpine (three-peak mountain snowflake) symbols, and TWI.

Key Test Requirements

High-Speed Performance Test

Drum diameter 1.7 m or 2.0 m; load = 85% of max rated load. For speed symbols F–S: 90 minutes continuous at 140 → 150 → 160 km/h (30 min each). For T–Y: staged test starting at ITS (rated speed minus 20 km/h), with 10–20 min steps up to rated speed. Pass criteria: no separation, chunking, cracks, or cord breaks; pressure after 15–25 min must be ≥95% of initial; outer diameter change after 2 hours within ±3.5%.

Strength Test

Hemispherical indentor (19 mm diameter) pressed at 50 mm/min into inflated tire. Minimum destruction energy:

Bead Unseating Resistance

Minimum unseating force applied at ≥4 points around circumference:

Endurance Test (Passenger Car)

On 1.7 m drum at 120 km/h (110 km/h for snow tires):

• 4 hours at 85% load
• 6 hours at 90% load
• 24 hours at 100% load

Followed immediately by 90 minutes low-pressure endurance. Pass: no separation, chunking, cracks, or cord breaks.

Rolling Noise Limits (dB(A))

Wet Grip Index (G) Minimum Requirements

Rolling Resistance Coefficient (Cr) Maximum

Severe snow tires get +1 N/kN allowance. Test at 80 km/h (C1/C2 LI≤121) or 60/80 km/h (C2/C3 LI>121), on a drum test stand using force, torque, or deceleration methods.

Severe Snow (Three-Peak Mountain Snowflake)

Three optional test methods: snow braking (C1), spin traction per ASTM F1805-06 (C1/C2), or snow acceleration (C3). Minimum Snow Grip index: C1 ≥1.07 (braking), C2 ≥1.02 (spin traction), C3 ≥1.25 (acceleration).

Speed Symbols

Key Takeaways

• Harmonization reduces cost: A single tire design meeting GTR-16 can be sold across multiple markets, cutting redundant testing and mold changes.
• Three performance pillars: safety (endurance, high-speed, strength, bead retention), environment (rolling resistance, noise), and grip (wet, snow).
• LT/C endurance remains non-harmonized: Two options remain — FMVSS-139 sequential test or UN-R54 (for Q-speed-and-below tires only).
• Transition period up to 10 years allowed to amortize mold changes (tire molds last 5–10 years; NHTSA estimates full turnover within 13 years).