Dirtytires
Explorer
sounds like tthe brakes are working if they "jerk". The best way to telll if they work properly is to hook the trailer to your tow vehicle and drive forward then slam on the brakes. If the surge brakes work then you will feel a pull not a slam. you can also have a person stand a distance behind you while doing this to see if the wheels on the trailer lock up. SOmetimes you need to open the cylinder, use a syringe to such out the rust and dirt sitting on the bottom. ALot of times the air and fluids being pushed through the lines clog them up.. Good luck.
