255/45R20 vs 285/35R21
285/35R21 is 5.0 mm shorter than 255/45R20 in overall diameter (−0.7%), within the usual 3% limit, so it can replace it where the wheels and clearance allow. With 285/35R21 fitted, the speedometer reads 100 km/h when you are doing 99.3 km/h.
Dimensions side by side
| 255/45R20 | 285/35R21 | |
|---|---|---|
| Overall diameter | 738 mm (29.1″) | 733 mm (28.9″) |
| Section width | 255 mm | 285 mm |
| Sidewall height | 115 mm | 100 mm |
| Rim | 20″ | 21″ |
| Revolutions per km | 431 | 434 |
| In stock | 81 tires from $173.00 | 4 tires from $408.00 |
What changes
- Overall diameter: 285/35R21 is 5.0 mm shorter (−0.7%).
- Speedometer: reads 100 km/h at an actual 99.3 km/h with 285/35R21.
- 285/35R21 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 255/45R20
Vehicles that use 285/35R21
See every alternate size for 255/45R20
Frequently asked questions
Can I use 285/35R21 instead of 255/45R20?
Usually, yes: 285/35R21 is within 3% of the overall diameter of 255/45R20 (−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 255/45R20 and 285/35R21?
With 285/35R21 instead of 255/45R20, the speedometer shows 100 km/h when you are actually doing 99.3 km/h.
Which vehicles came with both 255/45R20 and 285/35R21?
Both sizes were original equipment, on different trims or packages, on the 2017–2024 Mercedes-Benz GLC 43, 2023–2024 BMW i7, 2021–2024 Alfa Romeo Stelvio, 2023–2024 BMW 740i, 2023–2024 BMW 760i, 2024 BMW 750e.