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04 / WHEEL TOOLS

Wheel Offset Comparison

Current vs. new wheel position.

GEOMETRY CHECK

Your setup

A / Current
Example: 18x8.5 ET35 · Negative offset: ET-10
Enter separate dimensions
B / New
Example: 18x8.5 ET35 · Negative offset: ET-10
Enter separate dimensions

What changes

NOMINAL GEOMETRY

Example calculation. Replace these values with your setup.

Inner clearance change-13.3 mm

The new wheel sits closer to the suspension in the nominal model.

Nominal wheel geometry

Inner clearance change
-13.3 mm

Less space toward the car

Outer extension change
-0.7 mm

Farther inward

Where the wheel sits

Inner reach

Current / A
136.6 mm
New / B
150 mm
Change
+13.3 mm

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

ACurrent / A

Current / A: 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.

BNew / B

New / B: Inner reachInner reach: 150 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 reach150 mm
← Inside · toward carOutside · toward fender →

Band: nominal bead-seat width.

Inner clearance change-13.3 mm

Outer extension change-0.7 mm

Orange arrows show the selected measurement. Change your inputs to update the drawing. Values describe static geometry.
Geometry results
MeasurementCurrentNewChange
Inner clearance change——-13.3 mm
Outer extension change——-0.7 mm
203.2 mm215.9 mm+12.7 mm
35.0 mm42.0 mm+7.0 mm
136.6 mm150.0 mm+13.3 mm
66.6 mm65.9 mm-0.7 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.
CONTINUE WITH THIS SETUPAdd tires to this comparison Calculate new-wheel backspacing

Compare wheel width and offset together

Check how a replacement wheel moves the nominal inner and outer planes. A width change can matter even when the offset stays the same.

Example · 18x8 ET35 → 18x8.5 ET42

The new wheel reduces nominal inner clearance by 13.35 mm. Its outer bead-seat position moves inward by 0.65 mm, despite the wider nominal wheel width.

Wheel lips and the tire envelope can extend beyond these nominal planes.

Wheel comparison questions

What does a negative inner-clearance change mean?

The new nominal inner wheel plane reaches farther toward the suspension by that amount. It is a change in position, not a measurement of the remaining gap on a vehicle.

What does positive outer extension mean?

The new nominal outer plane sits farther outward from the same hub mounting reference. A negative value means it moves inward. The result does not include the tire or a measured wheel lip.

Can the wider wheel still sit farther inside the fender?

Yes. An offset increase can move the wheel inward enough to outweigh half of the added width. Evaluate the inner and outer changes together, then assess the tire envelope and actual clearances separately.

Methodology & limits

How this tool works

Inner clearance change = current inner reach − new inner reach. Outer extension change = new outer reach − current outer reach.