315/70R17 vs 305/70R17Tire Size Comparison

Safe

The 1.6% diameter difference is within the accepted 3% tolerance.

315/70R17873mm dia305/70R17859mm dia-7.0mm

Comparison Details

Overall Diameter872.8 vs 858.8 mm (-14.0 mm)
Diameter Difference-1.60%
Section Width315 vs 305 mm (-10 mm)
Sidewall Height220.5 vs 213.5 mm (-7.0 mm)
Circumference2742.0 vs 2698.0 mm
Clearance Change-7.0 mm
Speedometer Error-1.60%
Revs/Mile587 vs 596

Speedometer Correction

When switching from 315/70R17 to 305/70R17, your speedometer will differ from actual speed.

SpeedometerActual SpeedDifference
30 km/h29.5 km/h-0.5 km/h
40 km/h39.4 km/h-0.6 km/h
50 km/h49.2 km/h-0.8 km/h
60 km/h59.0 km/h-1.0 km/h
70 km/h68.9 km/h-1.1 km/h
80 km/h78.7 km/h-1.3 km/h
90 km/h88.6 km/h-1.4 km/h
100 km/h98.4 km/h-1.6 km/h
110 km/h108.2 km/h-1.8 km/h
120 km/h118.1 km/h-1.9 km/h
130 km/h127.9 km/h-2.1 km/h

Vehicles Using These Sizes

Vehicles with 315/70R17

2026 Ford F-150Raptor2026 Ford F-150Raptor R2025 Ford F-150Raptor2024 Ford F-150Raptor2023 Ford F-150Raptor2025 Ford BroncoWildtrak/Raptor2024 Ford BroncoWildtrak/Raptor2023 Ford BroncoWildtrak/Raptor2022 Ford BroncoWildtrak2021 Ford BroncoWildtrak

Practical Guidance

Switching from 315/70R17 to 305/70R17 is within the industry-accepted 3% diameter tolerance. Your speedometer, ABS, and traction control should function normally. Both sizes fit the same 17-inch rim, so no wheel change is needed.

The 3% diameter tolerance is a widely accepted industry guideline referenced by the ETRTO and most vehicle manufacturers. When in doubt, consult your vehicle's owner's manual or a qualified tire professional. For U.S. tire safety standards and recalls, see the NHTSA Tire Safety page.

Frequently Asked Questions

Safe. The overall diameter differs by -1.60%, width changes by -10mm.

Speedometer error will be -1.60%. At an indicated 100 km/h, actual speed is about 98.4 km/h.

Ground clearance changes by -7.0mm per side.