255/35R21 vs 255/40R20
255/40R20 is 0.0 mm taller than 255/35R21 in overall diameter (±0.0%), within the usual 3% limit, so it can replace it where the wheels and clearance allow. With 255/40R20 fitted, the speedometer reads 100 km/h when you are doing 100.0 km/h.
Dimensions side by side
| 255/35R21 | 255/40R20 | |
|---|---|---|
| Overall diameter | 712 mm (28.0″) | 712 mm (28.0″) |
| Section width | 255 mm | 255 mm |
| Sidewall height | 89 mm | 102 mm |
| Rim | 21″ | 20″ |
| Revolutions per km | 447 | 447 |
| In stock | 12 tires from $291.00 | 47 tires from $164.00 |
What changes
- Overall diameter: 255/40R20 is 0.0 mm taller (±0.0%).
- Speedometer: reads 100 km/h at an actual 100.0 km/h with 255/40R20.
- Wheel size changes from 21″ 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 255/35R21
Vehicles that use 255/40R20
See every alternate size for 255/35R21
Frequently asked questions
Can I use 255/40R20 instead of 255/35R21?
Usually, yes: 255/40R20 is within 3% of the overall diameter of 255/35R21 (±0.0%). 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 255/35R21 and 255/40R20?
With 255/40R20 instead of 255/35R21, the speedometer shows 100 km/h when you are actually doing 100.0 km/h.
Which vehicles came with both 255/35R21 and 255/40R20?
Both sizes were original equipment, on different trims or packages, on the 2019–2024 Audi A7, 2023–2024 Mercedes-Benz EQE350, 2021–2024 Mercedes-Benz GLA35, 2021–2024 Mercedes-Benz GLB35, 2022–2024 Mercedes-Benz S500, 2022–2024 Mercedes-Benz S580.