Nominal Ground Clearance Change Calculator
Estimate how much ground clearance changes with a new tire size. Half the diameter change, shown in mm and inches at the axle.
Estimate clearance changes from tire radius.
Nominal Ground Clearance Change Calculator: Tire Size Inputs
Compare two tire sizes here. Use the formulas and reference tables below for this tool's specific calculation.
How Nominal Ground Clearance Change Calculator Works?
The Nominal Ground Clearance Change Calculator works by taking half of the diameter change, which equals the change in tire radius, and adding that value to the stock clearance. The tool uses 3 steps.
Enter both sizes
Type the stock size (265/70 R17) and the new size (285/75 R17).
Find the radius change
The calculator halves the 56.5 mm diameter gain for a 28.3 mm (1.11 in) radius gain.
Add to stock clearance
Type the stock clearance, for example 235 mm (9.3 in). The calculator returns the new nominal clearance under the axle.
Nominal Ground Clearance Change Calculator Formula
The Nominal Ground Clearance Change Calculator formula is ΔGC = (OD_new − OD_old) ÷ 2.
ΔGC = (OD_new − OD_old) ÷ 2GC_new = GC_stock + ΔGCΔGC_in = ΔGC ÷ 25.4- ΔGC
- Change in clearance at the axle (mm)
- GC_stock
- Published stock ground clearance (mm)
Worked example
A 285/75 R17 tire is 56.5 mm (2.22 in) taller than 265/70 R17. The axle rises 28.3 mm (1.11 in). A truck with 235 mm (9.3 in) of stock clearance gets 263 mm (10.4 in) under the differential.
Nominal Ground Clearance Change Calculator Conversion Table
The Nominal Ground Clearance Change Calculator conversion table shows the clearance gain for 7 sizes on a truck with 235 mm (9.3 in) stock clearance.
| New size | Radius | Change (mm) | Change (in) | New clearance |
|---|---|---|---|---|
| 265/70 R17 | 401.4 mm | +0.0 mm | +0.00 in | 235 mm (9.3 in) |
| 265/75 R17 | 414.6 mm | +13.2 mm | +0.52 in | 248 mm (9.8 in) |
| 285/70 R17 | 415.4 mm | +14.0 mm | +0.55 in | 249 mm (9.8 in) |
| 275/70 R18 | 421.1 mm | +19.7 mm | +0.78 in | 255 mm (10.0 in) |
| 285/75 R17 | 429.6 mm | +28.2 mm | +1.11 in | 263 mm (10.4 in) |
| 305/70 R18 | 442.1 mm | +40.7 mm | +1.60 in | 276 mm (10.9 in) |
| 315/70 R17 | 436.4 mm | +35.0 mm | +1.38 in | 270 mm (10.6 in) |
What is Nominal Ground Clearance Change Calculator?
A Nominal Ground Clearance Change Calculator is a tool that estimates how much higher or lower the axles sit after a tire size change. Tires lift the whole vehicle, including the differentials, which suspension lifts do not raise.
Clearance changes by half the diameter change. A tire 2 in (50.8 mm) taller adds 1 in (25.4 mm) of clearance.
The result is nominal. Real clearance depends on loaded radius, tire pressure and payload.
What are the uses of Nominal Ground Clearance Change Calculator?
There are 4 main uses of the Nominal Ground Clearance Change Calculator, including off-road planning and lowered car checks.
Off-road planning
Measure the differential clearance gain from bigger tires.
Lowered car checks
Confirm a shorter tire does not drop the car below a safe height.
Ramp and curb checks
Check driveway and ramp clearance after a size change.
Combined lift math
Add tire lift to suspension lift for total height.
Related Clearance & Stance Tools
View All 134 Subtools →Compare manufacturer-specified loaded tire radii.
Estimate static vertical gap changes.
Estimate changes toward suspension components.
Estimate tire movement toward the fender.
Estimate changes at the inner wheel edge.
Estimate changes at the outer wheel edge.