225/45R18 vs 255/40R18
255/40R18 is 1.0 mm taller than 225/45R18 in overall diameter (+0.2%), within the usual 3% limit, so it can replace it where the wheels and clearance allow. With 255/40R18 fitted, the speedometer reads 100 km/h when you are doing 100.2 km/h.
Dimensions side by side
| 225/45R18 | 255/40R18 | |
|---|---|---|
| Overall diameter | 660 mm (26.0″) | 661 mm (26.0″) |
| Section width | 225 mm | 255 mm |
| Sidewall height | 101 mm | 102 mm |
| Rim | 18″ | 18″ |
| Revolutions per km | 482 | 482 |
| In stock | 95 tires from $112.00 | 13 tires from $238.00 |
What changes
- Overall diameter: 255/40R18 is 1.0 mm taller (+0.2%).
- Speedometer: reads 100 km/h at an actual 100.2 km/h with 255/40R18.
- 255/40R18 is 30 mm wider, so check clearance and the recommended rim width.
- Choose a load index at least as high as the one on your door placard.
Vehicles that came with both sizes
Vehicles that use 225/45R18
Vehicles that use 255/40R18
See every alternate size for 225/45R18
Frequently asked questions
Can I use 255/40R18 instead of 225/45R18?
Usually, yes: 255/40R18 is within 3% of the overall diameter of 225/45R18 (+0.2%). Use wheels of the right size and width, match or exceed the original load index, and check clearance at full steering lock.
How much does the speedometer change between 225/45R18 and 255/40R18?
With 255/40R18 instead of 225/45R18, the speedometer shows 100 km/h when you are actually doing 100.2 km/h.
Which vehicles came with both 225/45R18 and 255/40R18?
Both sizes were original equipment, on different trims or packages, on the 2021–2024 BMW M440i, 2006–2008, 2019–2024 BMW Z4, 2020–2024 BMW M340i, 2022–2024 BMW 230i, 2017–2020 BMW 440i, 2017–2020 BMW 430i.