Originally Posted by Martsing
What is a light trailer or heavy trailer setting? Is that something arrived at through experience or is there specific setting?
You arrive at the settings via testing. You need to read the owners manual on how to set it up correctly. There are also YouTube videos with information on how to do it. Each combination tow vehicle and trailer are different, so you will need to find what works best for your setup. You'll also need to adjust this setting every so often, so don't just set it and never look at it again.
If you set it too high, the trailer brakes will be constantly locking up when you brake and you'll go through brake pads and tires like mad! If too light, your tow vehicle does all the work and you won't be able to stop very well. In that case you'll also be replacing brakes shoes/pads in the tow vehicle very often.