Wheel Offset
Tires & Wheels · 6 specs
Direct Answer
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.
Source: SAE J109 / ETRTO Wheel Engineering Guidelines · Last reviewed Aug 28, 2026
Specs
| 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 |
Understanding Scrub Radius Dynamics
When modifying offset with aftermarket wheels or wheel spacers (e.g. going from stock ET+50 to ET+30), the tire contact patch moves 20 mm outward. This alters the vehicle's scrub radius (the intersection of the steering kingpin axis and the ground): an excessive positive scrub radius causes severe steering wheel kickback over bumps, tramlining in road ruts, and aggressive torque steer during hard acceleration.