If you are pulling a trailer I recommend using a brake control with double-axis accelerometer technology or like product. It will continually check and then adjust for varying road terrain. The brake controller technology also senses the vehicles rate of deceleration and applies a proportionate amount of braking power to the trailer as fast as is needed, for a safer smoother stop. I currantly have a Valley Odyssey (TM) Electric Trailer Brake Controller that I am very pleased with. You can never be to safe at 60 mph and a few tons of chemicals and steel attached to your trailer/pintle hitch.