205/50R17 vs 225/40R18
225/40R18 is 0.0 mm taller than 205/50R17 in overall diameter (±0.0%), within the usual 3% limit, so it can replace it where the wheels and clearance allow. With 225/40R18 fitted, the speedometer reads 100 km/h when you are doing 100.0 km/h.
Dimensions side by side
| 205/50R17 | 225/40R18 | |
|---|---|---|
| Overall diameter | 637 mm (25.1″) | 637 mm (25.1″) |
| Section width | 205 mm | 225 mm |
| Sidewall height | 103 mm | 90 mm |
| Rim | 17″ | 18″ |
| Revolutions per km | 500 | 500 |
| In stock | 35 tires from $103.00 | 77 tires from $110.00 |
What changes
- Overall diameter: 225/40R18 is 0.0 mm taller (±0.0%).
- Speedometer: reads 100 km/h at an actual 100.0 km/h with 225/40R18.
- 225/40R18 is 20 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 205/50R17
Vehicles that use 225/40R18
See every alternate size for 205/50R17
Frequently asked questions
Can I use 225/40R18 instead of 205/50R17?
Usually, yes: 225/40R18 is within 3% of the overall diameter of 205/50R17 (±0.0%). 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 205/50R17 and 225/40R18?
With 225/40R18 instead of 205/50R17, the speedometer shows 100 km/h when you are actually doing 100.0 km/h.
Which vehicles came with both 205/50R17 and 225/40R18?
Both sizes were original equipment, on different trims or packages, on the 2017–2021 BMW 230i, 2014–2016 BMW 228i, 1995–2005 Porsche 911, 2000–2004 Porsche Boxster.