Tire Load Index vs. Wheel Offset
Comparing 2 standards across 13 specifications. 13 key differences identified.
The Tire Load Index (standardized under ISO 4000-1) is a numerical code assigned to a passenger or commercial tire indicating the maximum physical weight (in kilograms and pounds) the tire can carry when inflated to its maximum operating cold tire pressure. Spanning Load Index 70 (335 kg / 739 lb) to Load Index 120 (1400 kg / 3086 lb) per tire.
Wheel Offset (denoted as ET from the German 'Einpresstiefe', measured in millimeters) is the distance from the wheel's true centerline to the mounting hub face. Dictating whether wheels tuck inside fenders (Positive ET), sit centered (Zero ET), or poke outwards (Negative ET), offset directly controls suspension scrub radius, steering stability, and brake caliper clearance.
Specification Comparison Table
13 Parameters| Parameter / Spec | ||
|---|---|---|
|
Standardization
|
ISO 4000-1 / ETRTO / TRA Load Tables | — |
|
Standard Load (SL) Pressure
|
Calibrated at 2.5 bar (36 psi) cold inflation pressure for passenger car tires | — |
|
Extra Load (XL / Reinforced)
|
Reinforced internal carcass calibrated at 2.9 bar (42 psi) for heavy electric vehicles (EVs) and SUVs | — |
|
Common Passenger Load Indices
|
LI 82: 475 kg (1,047 lb) | LI 88: 560 kg (1,235 lb) | LI 91: 615 kg (1,356 lb) | LI 95: 690 kg (1,521 lb) | — |
|
Heavy EV & SUV Load Indices
|
LI 100: 800 kg (1,764 lb) | LI 104: 900 kg (1,984 lb) | LI 108: 1,000 kg (2,205 lb) | LI 112: 1,120 kg (2,469 lb) | — |
|
Vehicle Axle Calculation
|
Sum of two tire load capacities on an axle must exceed the Gross Axle Weight Rating (GAWR) | — |
|
HL (High Load) EV Benchmark
|
New standard for heavy battery packs carrying higher load at equivalent tire volume and pressure | — |
|
Definition of Offset (ET)
|
— | Distance in millimeters from the physical geometric centerline of the wheel width to the mounting hub contact face |
|
Positive Offset (+ET, e.g. ET+45)
|
— | Hub face is located toward the outer street-facing side of the wheel (standard on front-wheel drive and modern AWD cars) |
|
Zero Offset (ET0)
|
— | Hub mounting face aligns exactly with the true centerline of the wheel width |
|
Negative Offset (-ET, e.g. ET-12)
|
— | Hub face is recessed toward the back/suspension side, pushing the wheel outwards into a deep-dish stance (lifted 4x4 trucks) |
|
Scrub Radius Impact
|
— | Decreasing positive offset pushes wheels outwards and creates positive scrub radius (increases steering kickback and torque steer) |
|
Brake Caliper Clearance (X-Factor)
|
— | Spoke curvature independent of ET that clears large Brembo multi-piston fixed brake calipers |