SPARE TIRE FIT GUIDE
From sidewall code to cover size.
Enter the code printed on your tire—such as 315/70R17. We calculate the tire's overall diameter and round it to the nearest available 27–35 inch cover size.
How to read the code
- 315 is section width in millimeters.
- 70 means each sidewall is 70% of the section width.
- R17 is the 17-inch rim—not the full tire diameter.
- For 315/70R17: (315 × 0.70 × 2) + (17 × 25.4) = 872.8 mm = 34.36 in.
Available cover sizes
27, 28, 29, 30, 31, 32, 33, 34, and 35 inches. Round to the nearest whole inch: 30.5 → 31, 32.7 → 33, and 32.1 → 32.
If the result is outside 26.5–35.49 inches or the code uses another format, contact us before ordering.
Shop spare tire covers →