255/55R18 vs 275/45R20
275/45R20 is 18.0 mm taller than 255/55R18 in overall diameter (+2.4%), within the usual 3% limit, so it can replace it where the wheels and clearance allow. With 275/45R20 fitted, the speedometer reads 100 km/h when you are doing 102.4 km/h.
Dimensions side by side
| 255/55R18 | 275/45R20 | |
|---|---|---|
| Overall diameter | 738 mm (29.1″) | 756 mm (29.8″) |
| Section width | 255 mm | 275 mm |
| Sidewall height | 140 mm | 124 mm |
| Rim | 18″ | 20″ |
| Revolutions per km | 431 | 421 |
| In stock | 27 tires from $160.00 | 50 tires from $166.00 |
What changes
- Overall diameter: 275/45R20 is 18.0 mm taller (+2.4%).
- Speedometer: reads 100 km/h at an actual 102.4 km/h with 275/45R20.
- 275/45R20 is 20 mm wider, so check clearance and the recommended rim width.
- Wheel size changes from 18″ to 20″: 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 255/55R18
Vehicles that use 275/45R20
See every alternate size for 255/55R18
Frequently asked questions
Can I use 275/45R20 instead of 255/55R18?
Usually, yes: 275/45R20 is within 3% of the overall diameter of 255/55R18 (+2.4%). 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 255/55R18 and 275/45R20?
With 275/45R20 instead of 255/55R18, the speedometer shows 100 km/h when you are actually doing 102.4 km/h.
Which vehicles came with both 255/55R18 and 275/45R20?
Both sizes were original equipment, on different trims or packages, on the 2011–2018 Porsche Cayenne, 2007–2015 Audi Q7, 2011 Volkswagen Touareg.