AWD Tire Matching Tool
Check that all four tires match for AWD. Use the calculator below. Results update as you type.
Max AWD Circumference delta: < 1.0% (typ. < 2/32" tread difference)How the AWD Tire Matching Tool Works
This tool works by converting a tread depth difference between tires into a circumference difference and comparing it with the vehicle maker's limit. It answers whether one new tire can join 3 worn tires.
- Enter the tire size, for example 235/65R17 (91.2 in circumference).
- Enter the new tire's tread depth, for example 10/32 in.
- Enter the worn tires' depth, for example 7/32 in.
- Read the gap: 3/32 in (2.38 mm) of tread, 0.589 in (15 mm) of circumference, or 0.65%.
The Formula
The formula is Circumference Gap = π × 2 × Tread Depth Gap. Tread loss happens on both the top and bottom of the tire, so the diameter shrinks by twice the depth.
Diameter Gap = 2 × Tread Gap Circumference Gap = π × Diameter Gap Gap (%) = Circumference Gap ÷ Circumference × 100 Max AWD Circumference delta: < 1.0% (typ. < 2/32" tread difference)Worked example: a 4/32 in (3.17 mm) tread gap gives a 0.785 in (19.9 mm) circumference gap. On a 91.2 in tire that is 0.86%.
Conversion Table
The conversion table converts tread gaps from 1/32 in to 8/32 in into circumference gaps for a 235/65R17. A 2/32 in gap equals 0.43%; an 8/32 in gap equals 1.72%.
The note under the table states the common maker limits of 2/32 in or 3/32 in. Your owner's manual sets the exact limit.
| Tread Gap (in) | Tread Gap (mm) | Circ Gap (in) | Circ Gap (mm) | Circ Gap (%) |
|---|---|---|---|---|
| 1/32 | 0.79 | 0.196 | 5.0 | 0.22% |
| 2/32 | 1.59 | 0.393 | 10.0 | 0.43% |
| 3/32 | 2.38 | 0.589 | 15.0 | 0.65% |
| 4/32 | 3.17 | 0.785 | 19.9 | 0.86% |
| 5/32 | 3.97 | 0.982 | 24.9 | 1.08% |
| 6/32 | 4.76 | 1.178 | 29.9 | 1.29% |
| 8/32 | 6.35 | 1.571 | 39.9 | 1.72% |
Many AWD makers publish a limit of 2/32 in or 3/32 in; the owner's manual sets the exact figure for each vehicle.
What Is the AWD Tire Matching Tool?
The AWD Tire Matching Tool is a tool that checks whether tires with different tread depths can run together on an all-wheel-drive vehicle. It applies to AWD, full-time 4WD and some electric vehicles with motors on both axles.
Worn tires are smaller than new tires. On an AWD vehicle, the size gap forces the center coupling to slip continuously, which can overheat clutches and fluid. Some tire shops shave a new tire's tread to match the worn set, and the tool tells you how much.
Common Uses
This tool has 4 uses: single-tire replacement, tire shaving, drivetrain protection and warranty checks.
- Replace one tire: See if one new tire is allowed.
- Plan tire shaving: Find how much tread to remove.
- Protect drivetrains: Keep coupling slip low.
- Check warranty rules: Match the maker's published limit.