[Chuckyarla]

Is it ok to use a slightly higher tyre profile in order to get a softer ride? For example 245/50/18 instead of 245/45/18.

[TEF]

I use 235/50-18 winter tires without problem. The higher profile improves ride (especially if one is switching from RFT to non-RFT tires) and provides additional protection to wheel damage from winter potholes. The downside is that the speedometer reads slightly slower than one's actual speed (i.e. reads 100 kph while actually traveling at 102 kph).

Just a thought though: Does the EU have rules for using non-standard tires on one's car?

[NTTY]

Originally Posted by Chuckyarla

Is it ok to use a slightly higher tyre profile in order to get a softer ride? For example 245/50/18 instead of 245/45/18.

You can't do that, the difference in diameter would be too high (+3.62%).
Generally, it is recommended to stay within 3% of the original diameter.

[NTTY]

Originally Posted by TEF

Just a thought though: Does the EU have rules for using non-standard tires on one's car?

Yes, with small variations between countries. Again, above 3% difference in diameter, there's a significant chance it's not authorized.

[TEF]

On both X3 and 535 xdrives, I have used tires (on all 4 wheels) 3.5% larger than spec. Provided the larger tires are on all four wheels, there are no issues (i.e. strange behavior, warning lights, handling problems). I am aware of the problems if one uses dissimilar tire sizes on an xdrive BMW, as different rolling diameters screws up vehicle's driveline and sensors. That said, I suspect that where you live, it's EU regulators that have the last word on this.