245/45R18 vs 275/30R20
275/30R20 is 5.0 mm shorter than 245/45R18 in overall diameter (−0.7%), within the usual 3% limit, so it can replace it where the wheels and clearance allow. With 275/30R20 fitted, the speedometer reads 100 km/h when you are doing 99.3 km/h.
Dimensions side by side
| 245/45R18 | 275/30R20 | |
|---|---|---|
| Overall diameter | 678 mm (26.7″) | 673 mm (26.5″) |
| Section width | 245 mm | 275 mm |
| Sidewall height | 110 mm | 83 mm |
| Rim | 18″ | 20″ |
| Revolutions per km | 469 | 473 |
| In stock | 50 tires from $118.00 | 14 tires from $269.00 |
What changes
- Overall diameter: 275/30R20 is 5.0 mm shorter (−0.7%).
- Speedometer: reads 100 km/h at an actual 99.3 km/h with 275/30R20.
- 275/30R20 is 30 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 245/45R18
Vehicles that use 275/30R20
See every alternate size for 245/45R18
Frequently asked questions
Can I use 275/30R20 instead of 245/45R18?
Usually, yes: 275/30R20 is within 3% of the overall diameter of 245/45R18 (−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 245/45R18 and 275/30R20?
With 275/30R20 instead of 245/45R18, the speedometer shows 100 km/h when you are actually doing 99.3 km/h.
Which vehicles came with both 245/45R18 and 275/30R20?
Both sizes were original equipment, on different trims or packages, on the 2024 Mercedes-Benz CLE300, 2020–2022 BMW 840i, 2012–2014 BMW 640i, 2014 BMW 650i.