Wheel width and offset compensation study
What ET preserves the outer or inner wheel edge?
This 26-row study uses the TireFitLab wheel engine to solve target ET from a reference 8J ET35 wheel across 6–12 inch widths, preserving one nominal edge at a time.
Method and formulas
Marked wheel width is converted to millimetres. Half of the width change is added to ET to preserve the outer edge or subtracted to preserve the inner edge.
outer: targetET = currentET + (targetWidthMm - currentWidthMm) / 2
inner: targetET = currentET - (targetWidthMm - currentWidthMm) / 2- Reference wheel: 8J ET35; no spacer.
- Width means nominal bead-seat width, not measured overall width.
- One nominal edge is preserved at a time; the opposite edge moves.
- Results do not establish vehicle, brake, suspension or arch clearance.
Calculated compensation table
| Target width | Preserved edge | Target ET | Outer change | Inner change |
|---|---|---|---|---|
| 6.0 in | Outer | ET9.6 | -0.0 mm | -50.8 mm |
| 6.0 in | Inner | ET60.4 | -50.8 mm | -0.0 mm |
| 6.5 in | Outer | ET16.0 | +0.0 mm | -38.1 mm |
| 6.5 in | Inner | ET54.0 | -38.1 mm | +0.0 mm |
| 7.0 in | Outer | ET22.3 | -0.0 mm | -25.4 mm |
| 7.0 in | Inner | ET47.7 | -25.4 mm | +0.0 mm |
| 7.5 in | Outer | ET28.6 | +0.0 mm | -12.7 mm |
| 7.5 in | Inner | ET41.4 | -12.7 mm | +0.0 mm |
| 8.0 in | Outer | ET35.0 | +0.0 mm | +0.0 mm |
| 8.0 in | Inner | ET35.0 | +0.0 mm | +0.0 mm |
| 8.5 in | Outer | ET41.4 | -0.0 mm | +12.7 mm |
| 8.5 in | Inner | ET28.6 | +12.7 mm | -0.0 mm |
| 9.0 in | Outer | ET47.7 | +0.0 mm | +25.4 mm |
| 9.0 in | Inner | ET22.3 | +25.4 mm | +0.0 mm |
| 9.5 in | Outer | ET54.0 | +0.0 mm | +38.1 mm |
| 9.5 in | Inner | ET16.0 | +38.1 mm | +0.0 mm |
| 10.0 in | Outer | ET60.4 | +0.0 mm | +50.8 mm |
| 10.0 in | Inner | ET9.6 | +50.8 mm | +0.0 mm |
| 10.5 in | Outer | ET66.8 | +0.0 mm | +63.5 mm |
| 10.5 in | Inner | ET3.3 | +63.5 mm | +0.0 mm |
| 11.0 in | Outer | ET73.1 | +0.0 mm | +76.2 mm |
| 11.0 in | Inner | ET-3.1 | +76.2 mm | +0.0 mm |
| 11.5 in | Outer | ET79.4 | +0.0 mm | +88.9 mm |
| 11.5 in | Inner | ET-9.4 | +88.9 mm | -0.0 mm |
| 12.0 in | Outer | ET85.8 | -0.0 mm | +101.6 mm |
| 12.0 in | Inner | ET-15.8 | +101.6 mm | -0.0 mm |
Download the complete dataset: JSON · CSV
Use these values for geometry screening only. Real wheels, tires, spokes, brakes and suspension require physical and manufacturer-specific verification.
Seasonal check
Planning a long summer drive?
Use the budget and running-cost tools before a trip, especially if the current tires are worn or the replacement size changes diameter.
- Technical check
- 2026-07-22
- Content updated
- 2026-07-22
What changed
- Published the engine-derived wheel-width and offset compensation study with JSON and CSV downloads.