245/50R18 vs 275/30R21
275/30R21 is 4.0 mm shorter than 245/50R18 in overall diameter (−0.6%), 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 99.4 km/h.
Dimensions side by side
| 245/50R18 | 275/30R21 | |
|---|---|---|
| Overall diameter | 702 mm (27.6″) | 698 mm (27.5″) |
| Section width | 245 mm | 275 mm |
| Sidewall height | 123 mm | 83 mm |
| Rim | 18″ | 21″ |
| Revolutions per km | 453 | 456 |
| In stock | 14 tires from $129.00 | 3 tires from $539.00 |
What changes
- Overall diameter: 275/30R21 is 4.0 mm shorter (−0.6%).
- Speedometer: reads 100 km/h at an actual 99.4 km/h with 275/30R21.
- 275/30R21 is 30 mm wider, so check clearance and the recommended rim width.
- Wheel size changes from 18″ 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 245/50R18
Vehicles that use 275/30R21
See every alternate size for 245/50R18
Frequently asked questions
Can I use 275/30R21 instead of 245/50R18?
Usually, yes: 275/30R21 is within 3% of the overall diameter of 245/50R18 (−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 245/50R18 and 275/30R21?
With 275/30R21 instead of 245/50R18, the speedometer shows 100 km/h when you are actually doing 99.4 km/h.
Which vehicles came with both 245/50R18 and 275/30R21?
Both sizes were original equipment, on different trims or packages, on the 2009–2015 BMW 750i, 2011–2015 BMW 740Li, 2009–2015 BMW 750Li.