It is not a race or geeky thing. It's there so that when you are towing a trailer you can lower the headlights. Usually it is supposed to be calibrated so that

It is not a race or geeky thing. It's there so that when you are towing a trailer you can lower the headlights. Usually it is supposed to be calibrated so that the highest position is the default no load in the back position, but you can recalibrate so that it is in the middle if you want.