235/65 x 17 tyres will give the best ride quality. 235/60 x 18 will probably be acceptable. 255/45 x 20 is just plain stupid for a vehicle of this type. Audi should not even offer this option. But sadly, if Audi didn't, the bling-obsessed idiots out there would go and buy them from someone else. The car itself is good to drive. Its most obvious competitor is the Volvo XC60 and maybe high spec versions of the Honda CR-V and Toyota RAV-4.