Depends on the bump, im lowered 40mm on fiat 15's. Im fine on most bumps, the only problem is the 'middle of the car' ie the exhaust whilst ur fronts are over but back arent. This only really happens to me on the really wank one foot long quite high ones
bumps what a waste of tarmac should be used to fill all the holes in the road that be betta way to get rid of there left ova tarmac not make speed bumps