Alloy wheels offset explained

The offset is the distance from the hub-mounting surface to the wheel's true center. It is quantified by an ET value and measured in mm. A positive offset means the hub-mounting surface is closer to the outside edge of the wheel, while a negative offset means the hub-mounting surface is closer to the inside edge of the wheel.

A wheel with too little positive offset will be closer to edge of the fender. This can cause clearance issues between the tire and the fender. One that has too much positive offset will be closer to the suspension components and could cause the tire to rub on them. Wheel width, offset, and its accompanying tire size all determine how a particular wheel/tire combination will fit on a given vehicle. Offset also affects the scrub radius of the steering, so it is advisable to follow the vehicle manufacturer`s advice. Because wheel offset changes the lever-arm length between the center of the tire and the centerline of the steering knuckle, the way bumps, road imperfections, and acceleration/braking forces turn into steering torques (bump-steer, torque-steer, etc.) and thus, will change the drivability of the vehicle depending on wheel offset. Likewise, the wheel bearings will see increased thrust loads if the wheel centerline is moved away from the bearing centerline.