Mechanical v’s Electric Braking Systems
Mechanical vs Electric Trailer Brakes
Your trailer brakes help slow the full vehicle and trailer combination, reducing the load placed on your tow vehicle’s brakes. The right system depends on your trailer’s weight, axle setup and how you plan to use it. Mechanical brakes suit many smaller trailers, while electric brakes give you more control when towing heavier loads.
When Does a Trailer Need Brakes?
In NSW, trailers up to 750kg Gross Trailer Mass, or GTM, do not need brakes. Trailers from 751kg to 2,000kg GTM need brakes on both wheels of at least one axle.
A trailer above 2,000kg GTM needs brakes on every wheel. The driver must be able to control the brakes from the normal driving position, and the trailer needs an automatic breakaway system. The breakaway system applies the brakes if the trailer separates from the tow vehicle.
These rules apply in NSW. Check with the road authority in your state or territory before changing your trailer braking system.
How Do Mechanical Trailer Brakes Work?
Mechanical trailer brakes usually operate through an overrun coupling. When you slow the tow vehicle, the trailer pushes forward against the coupling. A sliding shaft inside the coupling moves a cable or linkage, which then applies the trailer brakes.
As the pressure against the coupling reduces, the brakes release.
This system does not need an electric brake controller. It is commonly used on box trailers, boat trailers and smaller work trailers between 751kg and 2,000kg GTM.
Mechanical brakes have fewer electrical parts, but they still need regular attention. Brake cables can stretch, seize or fall out of adjustment. The coupling also needs enough movement to apply and release the brakes correctly.
How Do Electric Trailer Brakes Work?
Electric brakes use magnets inside the brake drums. When you press the tow vehicle’s brake pedal, a brake controller sends power to the trailer. The magnets move the internal brake parts, pressing the brake shoes against the drums.
You can adjust the braking force through the controller. This helps you match the brake response to the trailer’s weight, road conditions and driving speed.
Electric brakes are common on caravans, horse floats, car trailers and heavier work trailers. They also allow compatible trailer brakes to be applied separately from the tow vehicle’s brakes, which can help you manage trailer sway.
The system needs a working brake controller, suitable wiring and a reliable power supply. If one of these parts has a fault, the trailer brakes may not work as intended.
Proportional and Time-Delayed Controllers
A proportional brake controller measures how quickly your vehicle is slowing. It then sends a similar level of braking force to the trailer.
Light braking produces a gentle response. Hard braking applies more force. This usually feels smoother when you drive through changing traffic or tow on roads with hills.
A time-delayed controller starts applying the trailer brakes when you press the brake pedal. The braking force increases over a set period until it reaches the selected level.
Time-delayed units can suit basic towing setups, but you may need to adjust them more often when the trailer load changes.
Vehicle-Mounted and Trailer-Mounted Controllers
A vehicle-mounted controller is wired into the tow vehicle. It can suit drivers who regularly tow several electric-braked trailers with the same vehicle.
A trailer-mounted controller, such as an Elecbrakes unit, is fitted to the trailer. This can help when the same trailer is towed by different compatible vehicles.
Both options need the correct wiring and trailer plug connections. The plug pins carry signals between the vehicle, controller and trailer. If the brake wire connects to the wrong pin, your lights may work while the brakes do not.
Always follow the wiring diagram supplied with the controller. Do not rely on wire colour alone, especially if the trailer has been repaired or modified in the past.
Which Trailer Braking System Should You Choose?
Mechanical brakes may suit your trailer if it weighs less than 2,000kg GTM and you want a straightforward setup without a brake controller. They are also common on boat trailers, although saltwater exposure means you need to inspect and service the parts regularly.
Electric brakes suit heavier trailers and drivers who want to adjust the braking force from the tow vehicle. They are useful when trailer loads change or when you regularly tow through hills, traffic or windy areas.
Your choice should also account for the number of axles, the brakes already fitted, the trailer’s rated weight and your tow vehicle’s wiring. Avoid choosing a system from the trailer’s empty weight alone. Think about how much it will weigh once loaded with tools, vehicles, water, camping gear or other cargo.
Setting Up Electric Trailer Brakes
Follow the brake controller manufacturer’s setup process. Test the brakes at a low speed in a safe area without nearby traffic.
The trailer should help slow the combination without pushing the tow vehicle or locking its wheels. Increase the controller output if the trailer pushes forward during braking. Reduce the output if the trailer wheels lock too easily.
A controller adjustment will not repair damaged wiring, worn magnets or badly adjusted brake shoes. Check the full system if the braking force feels weak or uneven.
Get Advice from Total Trailer Parts
Total Trailer Parts stocks brake controllers, breakaway systems, backing plates, magnets, shoes, cables, plugs and other braking parts.
Before contacting our team, check your trailer’s GTM and ATM ratings, number of axles, brake size and current controller model. Photos of the coupling, brake assemblies, plug and compliance plate can also help us identify suitable parts.
FAQs
Can I use mechanical brakes on a tandem-axle trailer?
Mechanical overrun brakes may be used on a tandem trailer up to 2,000kg GTM. The brakes must operate on both wheels of at least one axle. Braking both axles may suit some trailers, but every part must have the correct rating. Above 2,000kg GTM, brakes are required on all wheels and an overrun-only system cannot be used in NSW.
Will electric trailer brakes work without a controller?
Standard electric trailer brakes need a controller to send the required power to the brake magnets. Connecting the trailer lights alone will not control the brakes. Some systems use a controller fitted inside the tow vehicle, while others place the controller on the trailer. Check the product instructions for its power supply, plug wiring and vehicle requirements.
Why does my trailer push the vehicle when braking?
The controller output may be too low, but worn brake parts or poor wiring can cause the same problem. Check the plug, earth connection, brake adjustment, magnets and drums before increasing the setting. The trailer load may also have changed since the controller was last adjusted. Test the system in a safe area after repairs or load changes.
How often should I check my trailer brakes?
Check the plug, visible wiring, cables and brake response before long towing trips. Follow the servicing interval supplied by the trailer, axle or brake manufacturer for a full inspection. Arrange an earlier check if you notice weak braking, wheel locking, pulling, unusual noise or heat near a wheel. Boat trailers may need more frequent attention after saltwater use.