235/50R18 vs 255/45R18
255/45R18 is 5.0 mm shorter than 235/50R18 in overall diameter (−0.7%), within the usual 3% limit, so it can replace it where the wheels and clearance allow. With 255/45R18 fitted, the speedometer reads 100 km/h when you are doing 99.3 km/h.
Dimensions side by side
| 235/50R18 | 255/45R18 | |
|---|---|---|
| Overall diameter | 692 mm (27.2″) | 687 mm (27.0″) |
| Section width | 235 mm | 255 mm |
| Sidewall height | 118 mm | 115 mm |
| Rim | 18″ | 18″ |
| Revolutions per km | 460 | 463 |
| In stock | 53 tires from $117.00 | 5 tires from $181.00 |
What changes
- Overall diameter: 255/45R18 is 5.0 mm shorter (−0.7%).
- Speedometer: reads 100 km/h at an actual 99.3 km/h with 255/45R18.
- 255/45R18 is 20 mm wider, so check clearance and the recommended rim width.
- Choose a load index at least as high as the one on your door placard.
Vehicles that came with both sizes
Vehicles that use 235/50R18
Vehicles that use 255/45R18
See every alternate size for 235/50R18
Frequently asked questions
Can I use 255/45R18 instead of 235/50R18?
Usually, yes: 255/45R18 is within 3% of the overall diameter of 235/50R18 (−0.7%). 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 235/50R18 and 255/45R18?
With 255/45R18 instead of 235/50R18, the speedometer shows 100 km/h when you are actually doing 99.3 km/h.
Which vehicles came with both 235/50R18 and 255/45R18?
Both sizes were original equipment, on different trims or packages, on the 2005–2011 Cadillac STS, 2004–2006 BMW X3, 1999–2001 BMW 740i, 2000–2001 BMW 740iL, 2000–2001 BMW 750iL, 2000 BMW 750i.