easiest way to picture it ?
When you are driving along the drive shaft rod will be spinining, the arb is connected to the drop links to hold it in place and keep the front end stiff. Depending on your arb if they loop over the drive shaft rod when you go over bumps, brake hard the car and suspension will pitch.
The drive shaft will move in a up and down manner, when going over a bump the drive shaft rod will move up thus getting closer to your arb, so to get round this you want to get arbs that go underneath the drive shaft rod e.g. whiteline
Once you replace the arb with after market ones you can raise your car lower or higher as much as you want, normally if the drive shaft rod is rubbing against the arb you will see a ring like the dirts warn away to fresh metal on your drive shaft rod directly opposite (under) the arb, tell tell signs, the knock normally happens when cornering hard, going over speed bumps, do as the guy suggested (paint) or easier full lock your steering wheel and look.
Its easy the drive shaft rod on one side of your car will be thicker and shorter then the other, its connected directly to your wheels, look at the thick side and you will see the arb going over the drive shaft rod in a loop sort off, have a good look.
