255/45R20 vs 265/40R21
265/40R21 is 7.0 mm taller than 255/45R20 in overall diameter (+0.9%), within the usual 3% limit, so it can replace it where the wheels and clearance allow. With 265/40R21 fitted, the speedometer reads 100 km/h when you are doing 100.9 km/h.
Dimensions side by side
| 255/45R20 | 265/40R21 | |
|---|---|---|
| Overall diameter | 738 mm (29.1″) | 745 mm (29.3″) |
| Section width | 255 mm | 265 mm |
| Sidewall height | 115 mm | 106 mm |
| Rim | 20″ | 21″ |
| Revolutions per km | 431 | 427 |
| In stock | 81 tires from $173.00 | 33 tires from $295.00 |
What changes
- Overall diameter: 265/40R21 is 7.0 mm taller (+0.9%).
- Speedometer: reads 100 km/h at an actual 100.9 km/h with 265/40R21.
- 265/40R21 is 10 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 255/45R20
Vehicles that use 265/40R21
See every alternate size for 255/45R20
Frequently asked questions
Can I use 265/40R21 instead of 255/45R20?
Usually, yes: 265/40R21 is within 3% of the overall diameter of 255/45R20 (+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 255/45R20 and 265/40R21?
With 265/40R21 instead of 255/45R20, the speedometer shows 100 km/h when you are actually doing 100.9 km/h.
Which vehicles came with both 255/45R20 and 265/40R21?
Both sizes were original equipment, on different trims or packages, on the 2022–2024 Mercedes-Benz EQS450, 2020–2024 BMW X3, 2020–2024 BMW X4, 2023–2024 Mercedes-Benz EQE350, 2023–2024 Mercedes-Benz EQE500, 2023–2024 Mercedes-Benz EQS580.