225/40R18 vs 255/40R17
255/40R17 is 1.0 mm shorter than 225/40R18 in overall diameter (−0.2%), within the usual 3% limit, so it can replace it where the wheels and clearance allow. With 255/40R17 fitted, the speedometer reads 100 km/h when you are doing 99.8 km/h.
Dimensions side by side
| 225/40R18 | 255/40R17 | |
|---|---|---|
| Overall diameter | 637 mm (25.1″) | 636 mm (25.0″) |
| Section width | 225 mm | 255 mm |
| Sidewall height | 90 mm | 102 mm |
| Rim | 18″ | 17″ |
| Revolutions per km | 500 | 500 |
| In stock | 77 tires from $110.00 | 5 tires from $225.00 |
What changes
- Overall diameter: 255/40R17 is 1.0 mm shorter (−0.2%).
- Speedometer: reads 100 km/h at an actual 99.8 km/h with 255/40R17.
- 255/40R17 is 30 mm wider, so check clearance and the recommended rim width.
- Wheel size changes from 18″ to 17″: 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 225/40R18
Vehicles that use 255/40R17
See every alternate size for 225/40R18
Frequently asked questions
Can I use 255/40R17 instead of 225/40R18?
Usually, yes: 255/40R17 is within 3% of the overall diameter of 225/40R18 (−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 225/40R18 and 255/40R17?
With 255/40R17 instead of 225/40R18, the speedometer shows 100 km/h when you are actually doing 99.8 km/h.
Which vehicles came with both 225/40R18 and 255/40R17?
Both sizes were original equipment, on different trims or packages, on the 2008–2009 BMW Z4, 1995–2005 Porsche 911, 2000–2004 Porsche Boxster.