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05 / WHEEL TOOLS

Wheel Offset Calculator

Wheel position from width and offset.

GEOMETRY CHECK

Your setup

Wheel dimensions
Example: 18x8.5 ET35 · Negative offset: ET-10
Enter separate dimensions

What changes

NOMINAL GEOMETRY

Example calculation. Replace these values with your setup.

Nominal inner reach136.6 mm

Nominal position around the hub

Nominal wheel geometry

Where the wheel sits

Inner reach

Your setup
136.6 mm

From the mounting face to the inside bead seat. More inner reach leaves less space toward the car.

01Your setup

Your setup: Inner reachInner reach: 136.6 mm. The gray band spans the nominal bead-seat planes. The dashed blue line is the wheel center; the solid orange line is the hub mounting face. Both comparison cards use one lateral scale. Band height is illustrative; physical wheel lips and a rim diameter are not inferred. Signed positions may lie on the same side of the mounting face.Wheel centerMounting faceInner reach136.6 mm
← Inside · toward carOutside · toward fender →

Band: nominal bead-seat width.

Orange arrows show the selected measurement. Change your inputs to update the drawing. Values describe static geometry.
Geometry results
MeasurementValue
203.2 mm
35.0 mm
136.6 mm
66.6 mm
Assumptions & limits
  • Nominal wheel planes use bead-seat width. They do not describe the outside lips unless physical dimensions are provided.
  • Positive inner clearance change means more room toward the suspension. Positive outer extension means farther toward the fender.

Understand positive and negative wheel offset

Calculate nominal inner and outer wheel reach from bead-seat width and signed offset. ET is the offset value in millimeters.

Example · 18x8 ET35

An 8-inch nominal width is 203.2 mm. With +35 mm offset, the nominal inner reach is 136.6 mm and the outer reach is 66.6 mm from the hub mounting plane.

These positions describe nominal bead-seat geometry, rather than the physical outside edges of the wheel lips.

Wheel offset questions

What does positive offset mean?

Positive offset places the hub mounting face toward the outside of the wheel’s nominal centerline. At the same width, a larger positive offset increases inner reach and reduces outer reach.

Does wheel diameter affect the calculated reach?

No. The lateral nominal positions use width and offset. Diameter is part of the wheel specification, but the calculation does not infer brake clearance from diameter or offset.

Is wheel offset the same as backspacing?

No. Offset is measured from the nominal wheel centerline to the mounting face. Backspacing uses the physical inboard edge, so it also needs an explicit overall-width or inner-flange measurement.

Methodology & limits

How this tool works

Nominal inner reach = nominal width / 2 + offset. Nominal outer reach = nominal width / 2 − offset. Convert wheel width from inches to millimeters first.