245/40R17 vs 255/35R18
255/35R18 is 8.0 mm taller than 245/40R17 in overall diameter (+1.3%), within the usual 3% limit, so it can replace it where the wheels and clearance allow. With 255/35R18 fitted, the speedometer reads 100 km/h when you are doing 101.3 km/h.
Dimensions side by side
| 245/40R17 | 255/35R18 | |
|---|---|---|
| Overall diameter | 628 mm (24.7″) | 636 mm (25.0″) |
| Section width | 245 mm | 255 mm |
| Sidewall height | 98 mm | 89 mm |
| Rim | 17″ | 18″ |
| Revolutions per km | 507 | 500 |
| In stock | 15 tires from $115.00 | 13 tires from $116.00 |
What changes
- Overall diameter: 255/35R18 is 8.0 mm taller (+1.3%).
- Speedometer: reads 100 km/h at an actual 101.3 km/h with 255/35R18.
- 255/35R18 is 10 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 245/40R17
Vehicles that use 255/35R18
See every alternate size for 245/40R17
Frequently asked questions
Can I use 255/35R18 instead of 245/40R17?
Usually, yes: 255/35R18 is within 3% of the overall diameter of 245/40R17 (+1.3%). 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 245/40R17 and 255/35R18?
With 255/35R18 instead of 245/40R17, the speedometer shows 100 km/h when you are actually doing 101.3 km/h.
Which vehicles came with both 245/40R17 and 255/35R18?
Both sizes were original equipment, on different trims or packages, on the 2012–2016 Mercedes-Benz C250, 2008–2015 Mercedes-Benz C350, 2008–2014 Mercedes-Benz C300, 2008–2009 Mercedes-Benz CLK550, 2002–2006 BMW 330Ci, 2002–2005 BMW 330i.