245/40R18 vs 245/45R17
245/45R17 is 1.0 mm shorter than 245/40R18 in overall diameter (−0.2%), within the usual 3% limit, so it can replace it where the wheels and clearance allow. With 245/45R17 fitted, the speedometer reads 100 km/h when you are doing 99.8 km/h.
Dimensions side by side
| 245/40R18 | 245/45R17 | |
|---|---|---|
| Overall diameter | 653 mm (25.7″) | 652 mm (25.7″) |
| Section width | 245 mm | 245 mm |
| Sidewall height | 98 mm | 110 mm |
| Rim | 18″ | 17″ |
| Revolutions per km | 487 | 488 |
| In stock | 62 tires from $119.00 | 18 tires from $113.00 |
What changes
- Overall diameter: 245/45R17 is 1.0 mm shorter (−0.2%).
- Speedometer: reads 100 km/h at an actual 99.8 km/h with 245/45R17.
- Wheel size changes from 18″ to 17″: 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 245/40R18
Vehicles that use 245/45R17
See every alternate size for 245/40R18
Frequently asked questions
Can I use 245/45R17 instead of 245/40R18?
Usually, yes: 245/45R17 is within 3% of the overall diameter of 245/40R18 (−0.2%). 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 245/40R18 and 245/45R17?
With 245/45R17 instead of 245/40R18, the speedometer shows 100 km/h when you are actually doing 99.8 km/h.
Which vehicles came with both 245/40R18 and 245/45R17?
Both sizes were original equipment, on different trims or packages, on the 2014–2019 Cadillac CTS, 2008–2016 Audi A4, 2010–2016 Mercedes-Benz E350, 2015 Mercedes-Benz E250, 2005–2011 Audi A6, 2008–2010 Audi A5.