225/50R17 vs 255/40R18
255/40R18 is 4.0 mm taller than 225/50R17 in overall diameter (+0.6%), 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 100.6 km/h.
Dimensions side by side
| 225/50R17 | 255/40R18 | |
|---|---|---|
| Overall diameter | 657 mm (25.9″) | 661 mm (26.0″) |
| Section width | 225 mm | 255 mm |
| Sidewall height | 113 mm | 102 mm |
| Rim | 17″ | 18″ |
| Revolutions per km | 484 | 482 |
| In stock | 51 tires from $111.00 | 13 tires from $238.00 |
What changes
- Overall diameter: 255/40R18 is 4.0 mm taller (+0.6%).
- Speedometer: reads 100 km/h at an actual 100.6 km/h with 255/40R18.
- 255/40R18 is 30 mm wider, so check clearance and the recommended rim width.
- Wheel size changes from 17″ to 18″: you need wheels in the new size.
- Choose a load index at least as high as the one on your door placard.
Vehicles that came with both sizes
Vehicles that use 225/50R17
Vehicles that use 255/40R18
See every alternate size for 225/50R17
Frequently asked questions
Can I use 255/40R18 instead of 225/50R17?
Usually, yes: 255/40R18 is within 3% of the overall diameter of 225/50R17 (+0.6%). 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 225/50R17 and 255/40R18?
With 255/40R18 instead of 225/50R17, the speedometer shows 100 km/h when you are actually doing 100.6 km/h.
Which vehicles came with both 225/50R17 and 255/40R18?
Both sizes were original equipment, on different trims or packages, on the 2017–2019 BMW 330i, 2016–2018 BMW 328d, 2017 BMW 330e, 2016 BMW 328i, 2014 BMW 320i.