245/40R20 vs 275/30R21
275/30R21 is 6.0 mm shorter than 245/40R20 in overall diameter (−0.9%), within the usual 3% limit, so it can replace it where the wheels and clearance allow. With 275/30R21 fitted, the speedometer reads 100 km/h when you are doing 99.1 km/h.
Dimensions side by side
| 245/40R20 | 275/30R21 | |
|---|---|---|
| Overall diameter | 704 mm (27.7″) | 698 mm (27.5″) |
| Section width | 245 mm | 275 mm |
| Sidewall height | 98 mm | 83 mm |
| Rim | 20″ | 21″ |
| Revolutions per km | 452 | 456 |
| In stock | 34 tires from $238.00 | 3 tires from $539.00 |
What changes
- Overall diameter: 275/30R21 is 6.0 mm shorter (−0.9%).
- Speedometer: reads 100 km/h at an actual 99.1 km/h with 275/30R21.
- 275/30R21 is 30 mm wider, so check clearance and the recommended rim width.
- Wheel size changes from 20″ to 21″: 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 245/40R20
Vehicles that use 275/30R21
See every alternate size for 245/40R20
Frequently asked questions
Can I use 275/30R21 instead of 245/40R20?
Usually, yes: 275/30R21 is within 3% of the overall diameter of 245/40R20 (−0.9%). 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 245/40R20 and 275/30R21?
With 275/30R21 instead of 245/40R20, the speedometer shows 100 km/h when you are actually doing 99.1 km/h.
Which vehicles came with both 245/40R20 and 275/30R21?
Both sizes were original equipment, on different trims or packages, on the 2024 BMW 530i, 2024 BMW i5, 2024 BMW 540i, 2024 Mercedes-Benz E350, 2024 Mercedes-Benz E450, 2009–2022 BMW 750i.