Hi,

On my 520d the factory tyre is the 225/50-17 runflat.
I was going to replace them with 225/55-17 regular type. This size is slighlty taller then the factory fitted tyres by about 0.5 inches (overall increase in diameter is 1 inch)
This would make ride more cushiony and also increase the ground clearence by about 11 mm.

================
Tyres