225/50R17 vs 245/40R18
245/40R18 is 4.0 mm shorter 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 245/40R18 fitted, the speedometer reads 100 km/h when you are doing 99.4 km/h.
Dimensions side by side
| 225/50R17 | 245/40R18 | |
|---|---|---|
| Overall diameter | 657 mm (25.9″) | 653 mm (25.7″) |
| Section width | 225 mm | 245 mm |
| Sidewall height | 113 mm | 98 mm |
| Rim | 17″ | 18″ |
| Revolutions per km | 484 | 487 |
| In stock | 51 tires from $111.00 | 62 tires from $119.00 |
What changes
- Overall diameter: 245/40R18 is 4.0 mm shorter (−0.6%).
- Speedometer: reads 100 km/h at an actual 99.4 km/h with 245/40R18.
- 245/40R18 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 225/50R17
Vehicles that use 245/40R18
See every alternate size for 225/50R17
Frequently asked questions
Can I use 245/40R18 instead of 225/50R17?
Usually, yes: 245/40R18 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 245/40R18?
With 245/40R18 instead of 225/50R17, the speedometer shows 100 km/h when you are actually doing 99.4 km/h.
Which vehicles came with both 225/50R17 and 245/40R18?
Both sizes were original equipment, on different trims or packages, on the 2008–2014, 2016–2024 Audi A4, 2017–2021 Mercedes-Benz C300, 2007–2015 Volvo S80, 2007–2012 Lexus GS, 2008–2010 BMW 535i, 2008–2010 BMW 528i.