Wheel offset calculator
Compare wheel width and offset to estimate how the inner and outer rim edges move. Positive offset moves the wheel inward.
Moves closer to the suspension; less inboard clearance.
Extends further outward.
Positive inner change uses more inboard clearance. Positive outer change adds outward extension. Compare these edge positions with the wheel maker’s dimensions and the vehicle’s available clearance.
Wheel position at the same mounting plane
Dashed line: wheel centerline. Positions are relative to the mounting plane: − inboard, + outboard.
A · Original
- Bead-seat width
- 203.20 mm8.00 in20.32 cm
- Offset · ET
- +35.00 mm+1.38 in+3.50 cm
- Inner edge position
- -136.60 mm-5.38 in-13.66 cm
- Outer edge position
- +66.60 mm+2.62 in+6.66 cm
B · New
- Bead-seat width
- 228.60 mm9.00 in22.86 cm
- Offset · ET
- +25.00 mm+0.98 in+2.50 cm
- Inner edge position
- -139.30 mm-5.48 in-13.93 cm
- Outer edge position
- +89.30 mm+3.52 in+8.93 cm
Photorealistic barrel-section illustration, cropped at nominal bead-seat boundaries. Both rows use the same horizontal scale. Vertical height is illustrative. Use the wheel maker’s drawing for diameter, flange shape, mounting-disk profile and brake clearance.
How we calculate it
Closer to suspension = Δ + ET B − ET A
Further outward = Δ − ET B + ET A
Example: 8 in ET35 → 9 in ET25 extends 2.7 mm (0.27 cm / 0.11 in) further inward and 22.7 mm (2.27 cm / 0.89 in) further outward. A negative result means movement in the opposite direction.
What to check before changing size
Use the vehicle and tire specifications to check these three points:
- Vehicle placard and manual: match an approved size and the required load and speed ratings.
- Wheel specifications: check the tire maker’s wheel-width range and the wheel offset.
- Available space: check clearance at full steering lock and throughout suspension travel.
Wheel width is measured between bead seats. Use the wheel maker’s drawing for overall width and flange shape; check the installed tire, steering travel, suspension movement and brake clearance.
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