235/45R18 vs 245/40R18Tire Size Comparison

Safe

The 2.3% diameter difference is within the accepted 3% tolerance.

235/45R18669mm dia245/40R18653mm dia-7.8mm

Comparison Details

Overall Diameter668.7 vs 653.2 mm (-15.5 mm)
Diameter Difference-2.32%
Section Width235 vs 245 mm (+10 mm)
Sidewall Height105.8 vs 98.0 mm (-7.8 mm)
Circumference2100.8 vs 2052.1 mm
Clearance Change-7.7 mm
Speedometer Error-2.32%
Revs/Mile766 vs 784

Speedometer Correction

When switching from 235/45R18 to 245/40R18, your speedometer will differ from actual speed.

SpeedometerActual SpeedDifference
30 km/h29.3 km/h-0.7 km/h
40 km/h39.1 km/h-0.9 km/h
50 km/h48.8 km/h-1.2 km/h
60 km/h58.6 km/h-1.4 km/h
70 km/h68.4 km/h-1.6 km/h
80 km/h78.1 km/h-1.9 km/h
90 km/h87.9 km/h-2.1 km/h
100 km/h97.7 km/h-2.3 km/h
110 km/h107.5 km/h-2.5 km/h
120 km/h117.2 km/h-2.8 km/h
130 km/h127.0 km/h-3.0 km/h

Vehicles Using These Sizes

Vehicles with 235/45R18

2025 Acura IntegraBase2025 Acura IntegraA-Spec Technology2024 Acura IntegraBase2024 Acura IntegraA-Spec Technology2023 Acura IntegraA-Spec Technology2025 Honda AccordSport/EX-L2024 Honda AccordSport/EX-L2023 Honda AccordSport/EX-L/Touring2022 Honda AccordSport/EX-L/Touring2021 Honda AccordSport/EX-L/Touring2020 Honda AccordSport/EX-L/Touring2026 Tesla Model 3Standard Range RWD2026 Tesla Model 3Long Range RWD2026 Tesla Model 3Long Range AWD2025 Tesla Model 3Standard Range/Long Range2024 Tesla Model 3Standard Range/Long Range2023 Tesla Model 3Standard Range Plus/Long Range2022 Tesla Model 3Standard Range Plus/Long Range2021 Tesla Model 3Standard Range Plus/Long Range2020 Tesla Model 3Standard Range Plus/Long Range2026 Toyota CamrySE2026 Toyota CamryXLE/XSE2025 Toyota CamrySE2025 Toyota CamryXLE/XSE2024 Toyota CamrySE/XSE2024 Toyota CamryXLE2023 Toyota CamryXLE/TRD2022 Toyota CamryXLE/TRD2021 Toyota CamryXLE/TRD2020 Toyota CamryXLE/TRD2025 Volvo S60Plus B5 AWD2024 Volvo S60Plus B5 AWD

Vehicles with 245/40R18

2025 Audi A4Premium 40 TFSI2025 Audi A4Premium Plus 45 TFSI quattro2024 Audi A4Premium Plus 45 TFSI quattro2023 Audi A4Premium Plus 45 TFSI quattro2022 Audi A4Premium Plus 45 TFSI quattro2021 Audi A4Premium Plus 45 TFSI quattro2020 Audi A4Premium Plus 45 TFSI quattro2025 Mercedes-Benz C-ClassC 3002025 Mercedes-Benz C-ClassC 300 4MATIC2024 Mercedes-Benz C-ClassC 3002024 Mercedes-Benz C-ClassC 300 4MATIC2023 Mercedes-Benz C-ClassC 3002023 Mercedes-Benz C-ClassC 300 4MATIC

Individual Tire Size Details

235/45R18
Full specifications, compatible vehicles, and alternatives
245/40R18
Full specifications, compatible vehicles, and alternatives

Practical Guidance

Switching from 235/45R18 to 245/40R18 is within the industry-accepted 3% diameter tolerance. Your speedometer, ABS, and traction control should function normally. Both sizes fit the same 18-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 -2.32%, width changes by 10mm.

Speedometer error will be -2.32%. At an indicated 100 km/h, actual speed is about 97.7 km/h.

Ground clearance changes by -7.7mm per side.