[TireFitLab](https://tirefitlab.com/) › [Tire & wheel reference guides](https://tirefitlab.com/learn/) › Wheel width and offset compensation study # 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](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=6Jx18%20ET9.6) | -0.0 mm | -50.8 mm | | 6.0 in | Inner | [ET60.4](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=6Jx18%20ET60.4) | -50.8 mm | -0.0 mm | | 6.5 in | Outer | [ET16.0](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=6.5Jx18%20ET16.0) | +0.0 mm | -38.1 mm | | 6.5 in | Inner | [ET54.0](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=6.5Jx18%20ET54.0) | -38.1 mm | +0.0 mm | | 7.0 in | Outer | [ET22.3](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=7Jx18%20ET22.3) | -0.0 mm | -25.4 mm | | 7.0 in | Inner | [ET47.7](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=7Jx18%20ET47.7) | -25.4 mm | +0.0 mm | | 7.5 in | Outer | [ET28.6](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=7.5Jx18%20ET28.6) | +0.0 mm | -12.7 mm | | 7.5 in | Inner | [ET41.4](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=7.5Jx18%20ET41.4) | -12.7 mm | +0.0 mm | | 8.0 in | Outer | [ET35.0](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=8Jx18%20ET35.0) | +0.0 mm | +0.0 mm | | 8.0 in | Inner | [ET35.0](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=8Jx18%20ET35.0) | +0.0 mm | +0.0 mm | | 8.5 in | Outer | [ET41.4](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=8.5Jx18%20ET41.4) | -0.0 mm | +12.7 mm | | 8.5 in | Inner | [ET28.6](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=8.5Jx18%20ET28.6) | +12.7 mm | -0.0 mm | | 9.0 in | Outer | [ET47.7](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=9Jx18%20ET47.7) | +0.0 mm | +25.4 mm | | 9.0 in | Inner | [ET22.3](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=9Jx18%20ET22.3) | +25.4 mm | +0.0 mm | | 9.5 in | Outer | [ET54.0](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=9.5Jx18%20ET54.0) | +0.0 mm | +38.1 mm | | 9.5 in | Inner | [ET16.0](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=9.5Jx18%20ET16.0) | +38.1 mm | +0.0 mm | | 10.0 in | Outer | [ET60.4](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=10Jx18%20ET60.4) | +0.0 mm | +50.8 mm | | 10.0 in | Inner | [ET9.6](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=10Jx18%20ET9.6) | +50.8 mm | +0.0 mm | | 10.5 in | Outer | [ET66.8](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=10.5Jx18%20ET66.8) | +0.0 mm | +63.5 mm | | 10.5 in | Inner | [ET3.3](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=10.5Jx18%20ET3.3) | +63.5 mm | +0.0 mm | | 11.0 in | Outer | [ET73.1](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=11Jx18%20ET73.1) | +0.0 mm | +76.2 mm | | 11.0 in | Inner | [ET-3.1](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=11Jx18%20ET-3.1) | +76.2 mm | +0.0 mm | | 11.5 in | Outer | [ET79.4](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=11.5Jx18%20ET79.4) | +0.0 mm | +88.9 mm | | 11.5 in | Inner | [ET-9.4](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=11.5Jx18%20ET-9.4) | +88.9 mm | -0.0 mm | | 12.0 in | Outer | [ET85.8](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=12Jx18%20ET85.8) | -0.0 mm | +101.6 mm | | 12.0 in | Inner | [ET-15.8](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=12Jx18%20ET-15.8) | +101.6 mm | -0.0 mm | Download the complete dataset: [JSON](https://tirefitlab.com/data/wheel-width-offset-study.json) · [CSV](https://tirefitlab.com/data/wheel-width-offset-study.csv) Use these values for geometry screening only. Real wheels, tires, spokes, brakes and suspension require physical and manufacturer-specific verification. [Wheel offset (ET) decoder](https://tirefitlab.com/wheel-offset-calculator/?old=8Jx18%20ET35&new=8Jx18%20ET35.0) 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. [Estimate tire budget](https://tirefitlab.com/tire-budget-calculator/) ## More in this topic: Wheel fitment depth Rim, offset, spacer and bolt-pattern guides for physical fitment checks. - [**Bolt pattern guide** Find which bolt pattern your car uses and which wheels are compatible. PCD tables for 4x100, 5x112, 5x114.3 and more.](https://tirefitlab.com/learn/bolt-pattern/) - [**Rim diameter guide** Find which tire sizes fit each rim diameter from 14 to 22 inches.](https://tirefitlab.com/learn/rim/) - [**Rim types and materials guide** Rim types explained: steel stamped, cast aluminium alloy, flow-formed alloy, forged alloy, carbon fibre. Weight comparison, heat dissipation, repair cost, corrosion resistance, and which type suits which driving application.](https://tirefitlab.com/learn/rim-types/) - [**Rim width and tire fitment guide** Use an editorial rim-width screening chart, then verify the approved range for the exact tire product, vehicle clearance and wheel specification.](https://tirefitlab.com/learn/rim-width-tyre-fitment/) ### 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. [Methodology](https://tirefitlab.com/methodology/)