i have a 7' x 14' tandem trailer i purchased about a month ago. they set me up with the tekonsha p3 brake controller. never had a trailer with brakes and i'm not sure what i should be looking for when "dialing" in the settings. i've tried different settings since i've had it but it still seems to lock up the tires when i feel it shouldn't. any help or advice would be helpfull.