255/35R19 vs 275/30R20Tire Size Comparison

Safe

The 1.8% diameter difference is within the accepted 3% tolerance.

255/35R19661mm dia275/30R20673mm dia+5.9mm

Comparison Details

Overall Diameter661.1 vs 673.0 mm (+11.9 mm)
Diameter Difference+1.80%
Section Width255 vs 275 mm (+20 mm)
Sidewall Height89.3 vs 82.5 mm (-6.8 mm)
Circumference2076.9 vs 2114.3 mm
Clearance Change+5.9 mm
Speedometer Error+1.80%
Revs/Mile775 vs 761

Speedometer Correction

When switching from 255/35R19 to 275/30R20, your speedometer will differ from actual speed.

SpeedometerActual SpeedDifference
30 km/h30.5 km/h+0.5 km/h
40 km/h40.7 km/h+0.7 km/h
50 km/h50.9 km/h+0.9 km/h
60 km/h61.1 km/h+1.1 km/h
70 km/h71.3 km/h+1.3 km/h
80 km/h81.4 km/h+1.4 km/h
90 km/h91.6 km/h+1.6 km/h
100 km/h101.8 km/h+1.8 km/h
110 km/h112.0 km/h+2.0 km/h
120 km/h122.2 km/h+2.2 km/h
130 km/h132.3 km/h+2.3 km/h

Vehicles Using These Sizes

Vehicles with 255/35R19

2025 BMW 3 SeriesM340i/M340i xDrive2024 BMW 3 SeriesM340i/M340i xDrive2023 BMW 3 SeriesM340i/M340i xDrive2022 BMW 3 SeriesM340i/M340i xDrive2021 BMW 3 SeriesM340i/M340i xDrive2020 BMW 3 SeriesM340i/M340i xDrive2025 Cadillac CT5V-Series2025 Genesis G703.3T2025 Mercedes-Benz C-ClassAMG C 432024 Mercedes-Benz C-ClassAMG C 432023 Mercedes-Benz C-ClassAMG C 432022 Mercedes-Benz C-ClassAMG C 432021 Mercedes-Benz C-ClassAMG C 432020 Mercedes-Benz C-ClassAMG C 43

Vehicles with 275/30R20

2026 Tesla Model 3Performance AWD

Individual Tire Size Details

255/35R19
Full specifications, compatible vehicles, and alternatives
275/30R20
Full specifications, compatible vehicles, and alternatives

Practical Guidance

Switching from 255/35R19 to 275/30R20 is within the industry-accepted 3% diameter tolerance. Your speedometer, ABS, and traction control should function normally. Note: these sizes require different rim diameters (19" vs 20"), so you will need different wheels.

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 1.80%, width changes by 20mm.

Speedometer error will be 1.80%. At an indicated 100 km/h, actual speed is about 101.8 km/h.

Ground clearance changes by +5.9mm per side.