Wheel offset explained: ET, poke, and inner movement

Wheel offset is the distance between the wheel centerline and its hub-mounting surface, measured in millimeters. ET+45 means positive 45 mm. Zero offset places the mounting surface on the centerline; negative offset moves it toward the inner side of the wheel. Tire Rack explains the offset convention.

Does lower offset move a wheel outward?

At the same width, yes. Changing ET45 to ET35 moves both edges 10 mm outward. The outer edge projects 10 mm farther toward the fender, while the inner edge moves 10 mm away from the suspension. This is a relative position change, not a measurement of clearance left on the vehicle.

Wheel width changes the answer

Compare an 8-inch ET45 wheel with a 9-inch ET35 wheel. The extra inch adds 25.4 mm of nominal width, or 12.7 mm on each side of the centerline. The 10 mm offset reduction then shifts the wheel outward.

Outer wheel edge

22.7 mm farther toward the fender

Inner wheel edge

2.7 mm farther toward the suspension

Despite the lower offset, the wider wheel moves its inner edge closer to the suspension in this example. Looking only at ET would miss that change. The formulas are outer = width × 25.4 ÷ 2 − ET and inner = width × 25.4 ÷ 2 + ET. Subtract current from proposed for each edge.

Inspect the 8-inch ET45 to 9-inch ET35 example

Offset, backspacing, and tire width are different

Backspacing is measured from the mounting surface to the wheel's inner edge. Nominal wheel width is measured between bead seats, so calculating an exact overall backspacing value requires the wheel's flange dimensions too. FitMyTires reports relative nominal wheel-edge changes and does not invent flange thickness.

The tire can extend beyond the wheel, and its mounted section width depends on the measuring rim and model. Enter the actual tire sizes as well as wheel widths and offsets to inspect estimated tire-edge movement. An unchanged outer tire edge does not prove that the inner edge stayed still.

What the drawing cannot check

The mounting plane gives both setups a common reference. No fender or suspension outline is measured from your vehicle. Brake clearance, hub and fastener compatibility, approved rim width, steering lock, and movement under load still need checking. Read the position model's limits before using the comparison to choose parts.