From my knowledge there's no hard and fast rule. Some take 40 profile tyres better than others. Mine rubs lightly on the headlight access panel, but other than that it's fine on 40's.
Yes it really depends on the ride height of the car. Mines always been reasonably high so even switching from 225/35 to 225/40 R888s (which are very square shouldered) I've never had any rubbing.