235/45R20 vs 235/55R18
235/55R18 is 4.0 mm shorter than 235/45R20 in overall diameter (−0.6%), within the usual 3% limit, so it can replace it where the wheels and clearance allow. With 235/55R18 fitted, the speedometer reads 100 km/h when you are doing 99.4 km/h.
Dimensions side by side
| 235/45R20 | 235/55R18 | |
|---|---|---|
| Overall diameter | 720 mm (28.3″) | 716 mm (28.2″) |
| Section width | 235 mm | 235 mm |
| Sidewall height | 106 mm | 129 mm |
| Rim | 20″ | 18″ |
| Revolutions per km | 442 | 445 |
| In stock | 17 tires from $132.00 | 60 tires from $128.00 |
What changes
- Overall diameter: 235/55R18 is 4.0 mm shorter (−0.6%).
- Speedometer: reads 100 km/h at an actual 99.4 km/h with 235/55R18.
- Wheel size changes from 20″ to 18″: 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 235/45R20
Vehicles that use 235/55R18
See every alternate size for 235/45R20
Frequently asked questions
Can I use 235/55R18 instead of 235/45R20?
Usually, yes: 235/55R18 is within 3% of the overall diameter of 235/45R20 (−0.6%). 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 235/45R20 and 235/55R18?
With 235/55R18 instead of 235/45R20, the speedometer shows 100 km/h when you are actually doing 99.4 km/h.
Which vehicles came with both 235/45R20 and 235/55R18?
Both sizes were original equipment, on different trims or packages, on the 2020–2024 Mercedes-Benz GLB250, 2021–2024 Mercedes-Benz GLA250, 2020 Mercedes-Benz GLA 250.