arb problems are different on everyones car tbh. general rule is around 40 mm. however mine is lowered 100mm and still only rubs on very full lock (i.e the last 2cm of turning the steering wheel) (will be raising it 20mm soon (as at 80-90mm ive never had rubbing) to stop this so i dont nak my steering rack untill i get the vrs arb from a mate)
sump problems, depends were you live, i have a bit of a problem in darlington cause some of the speed bumps around there are large, however some of the speedbumps were i work are tiny so have no problem, you will soon learn what you can and cant go over and how fast to take speed bumps