A trailer can be a real asset when you’re planning a longer trip, but if it wants to keep going when you stop your vehicle it quickly turns into a bit of a liability. A small trailer without too much mass will stop on its own pretty well, but larger ones need a braking system – and the law says that any trailer over 750kg must be fitted with brakes.
There are two main options for trailer braking systems. One is inertia brakes. These have a device – usually a pendulum – that senses when the tow vehicle is slowing down and applies the trailer’s brakes. Inertia brakes work well on roads, but they tend to glitch on rougher ground. If the trailer isn’t level the system can misinterpret the pendulum’s movements as deceleration, and put the brakes on when you don’t want them.