Nearly every caravan sold in Australia has electric brakes, and electric brakes do nothing until something in the car tells them how hard to work. That something is a brake controller. It is a small box or dial, it is the single most important piece of towing equipment after the towbar itself, and it is the one most often bought on the wrong basis.
This page covers the law by weight band, the two controller types and why one of them is almost always the right buy, the factory-fitted check that can save you an installation entirely, and what an install involves.
What the law requires, by weight
Australian trailer braking law is set federally by the trailer brake design rule (ADR 38/05) and applied on-road by every state and territory through the same model rules, so the thresholds below are the same nationwide. They are written in GTM, not ATM.
| Trailer weight | Required braking | Worth knowing |
|---|---|---|
| Up to 750kg GTM | No brakes required. | If brakes are fitted anyway, they must comply with the standards. Very few caravans sit here; this band is mostly box trailers and the smallest campers. |
| 751 to 2,000kg GTM | An efficient braking system on both wheels of at least one axle. | Over-run (override) brakes are permitted in this band, and they need no controller in the car. This is why small camper trailers tow without one. |
| Over 2,000kg GTM | Brakes on every wheel, workable by the driver from the normal driving position, plus a breakaway system. | The breakaway system must apply the van's brakes automatically if it detaches, and the brakes must stay applied for at least 15 minutes. Over-run brakes are not permitted here. |
GTM and ATM are not the same number
GTM (gross trailer mass) is the weight carried by the van's wheels while it is hitched to the car. ATM (aggregate trailer mass) is the van's total loaded weight, including the share resting on the towball. So GTM is roughly ATM minus ball weight, and the legal brake thresholds all use GTM. In practice the distinction rarely changes the answer for a caravan: a van with a 2,500kg ATM and a 250kg ball weight still has a GTM around 2,250kg, well over the 2,000kg line.
Why "do I need a controller" is really one question
No law names a brake controller. The rules say the van's brakes must respond to a control signal from the tow vehicle and, over 2,000kg GTM, be workable by the driver from the normal driving position. With electric brakes, a controller is the only way to do that. So if your van has electric brakes and no controller is fitted, the van's brakes are not working at all, and the rig is neither legal nor safe to tow.
Proportional vs time-delayed
Every controller on the market is one of two types, and the type matters more than the brand.
Proportional
Senses how hard the car is decelerating and applies the van's brakes to match, continuously. Brake gently and the van brakes gently. Stand on the pedal and the van stands on its own brakes at the same moment.
The rig slows as one unit, which means less pushing from behind, less brake wear on the car, and a far better chance of keeping everything straight in an emergency stop. This is the type to fit.
Time-delayed
Applies a preset braking level a moment after you touch the pedal, at the same strength every time, no matter how hard the car itself is braking.
Simpler and usually cheaper, and it will pass a roadworthy. But the van is always braking either harder or softer than the car, which you feel as a nudge or a tug at every stop, and the mismatch is largest exactly when you brake hardest.
Controllers also differ in where they live. Traditional units mount on or under the dash. Remote-head designs hide the electronics and leave only a small dial on the dash. A newer class mounts on the trailer itself and is controlled from a phone or a small remote, which suits a leased or shared car, and sidesteps dash-mounting around airbags entirely. All three can be proportional, so pick the type first and the mounting style second.
The gain dial, in one paragraph
Every controller has a gain setting: how hard the van brakes for a given push on the pedal. Set it with the van loaded as you actually tow, following the unit's procedure, in a quiet flat area. Too low and the car does all the work while the van pushes it from behind. Too high and the van's wheels lock and drag. Re-check it when the load changes materially, not just when you first fit the unit.
Check whether your car already has one
A growing number of vehicles sold in Australia can be ordered with the brake controller built into the vehicle's own electronics, with the controls in the dash and the display in the instrument cluster. If your car has one, you do not need to buy or install anything, and the integrated unit is calibrated to the car's own braking. Manufacturer-confirmed examples at the time of writing:
Ford Ranger and Everest
Ford Australia lists an optional factory-fitted integrated trailer brake controller for both. Whether it is on your build depends on the grade and options, so check the build sheet.
Toyota Tundra
Toyota Australia lists an integrated trailer brake controller as standard equipment.
Chevrolet Silverado 1500 and 2500 HD
GMSV's Australian specifications list an electric trailer brake controller on the local variants, with brake gain memory on the integrated unit.
Lists like this date quickly, and fitment changes by model year and grade. The reliable check is the towing section of your car's build sheet or the maker's online configurator, looking for the words "integrated trailer brake controller", or asking the dealer to confirm in writing. Doing that check before booking an aftermarket install is the cheapest five minutes in caravanning.
What installation involves
An aftermarket install is routine work for an auto electrician or towbar fitter, and it has three parts: a fused power feed from the battery, a brake output wire to the trailer socket, and the mounting. If the car was ordered with a factory tow pack, the wiring is often already pre-pinned behind the dash and the job shrinks accordingly.
After fitting, the installer should set the gain with your van attached and loaded, and show you how to re-set it yourself. If you are quoted for an install, ask whether that calibration drive is included.
Where the unit mounts is a safety rule, not a preference
State vehicle-standards guidance requires dash accessories to sit clear of airbag deployment zones and the driver's view of the road, and a brake controller also needs its manual override slide within easy reach of the driver. Modern dashes leave few spots that satisfy all three, which is one of the better arguments for professional fitting, a remote-head unit, or a trailer-mounted one.
Where to buy one
Checked your car does not already have one, and settled on proportional? Any towing specialist, auto electrician or caravan accessory retailer will carry the common units.
Browse electric brake controllers at Caravan RV Camping (an affiliate link, and buying through it can earn us a commission). Whatever the retailer, buy on type and on your van's axle count, and have the install quoted at the same time.
Towing mirrors and a weight distribution hitch usually get bought in the same trip: the full run-through is in the essential accessories guide.
Common questions about brake controllers
Do I legally need a brake controller for my caravan?
No Australian law names a brake controller. What the law requires is that a van over 750kg GTM has working brakes, and that over 2,000kg GTM the driver can work those brakes from the driving position. If your van has electric brakes, a controller in the car is the only way to meet that, so in practice the answer for nearly every full-size caravan is yes. The exception is over-run brakes, which are permitted up to 2,000kg GTM and need nothing in the car.
Is the 750kg brake threshold ATM or GTM?
GTM, in every state and territory. GTM is the weight on the van's wheels while it is coupled to the car, so it is lower than ATM, which is the van's total loaded weight including what rests on the towball. The federal design rule, the model national rules and every state guide all set the brake thresholds in GTM.
What is a breakaway system and when is it required?
A breakaway system applies the van's brakes automatically if the van comes off the car, and the rules require the brakes to stay applied for at least 15 minutes. It is required on any trailer over 2,000kg GTM, which covers nearly every caravan on this site. It runs from its own battery on the van, so checking that battery is charged belongs on your pre-trip list.
Should I buy a proportional or a time-delayed controller?
Proportional, unless something specific rules it out. A proportional controller senses how hard the car is braking and applies the van's brakes to match, so the rig slows as one unit. A time-delayed controller applies a preset braking level after a short delay regardless of how hard you are braking, which is workable but noticeably less smooth, especially in an emergency stop.
Does my new ute already have a brake controller built in?
Some current models do. Ford lists an optional factory integrated controller for Ranger and Everest, and Toyota's Tundra and GMSV's Silverado list one as standard. Factory fitment changes by model year and grade, so the reliable check is the towing section of your build sheet or the maker's configurator, or ask the dealer to confirm in writing before you pay for an aftermarket install.
Can I fit a brake controller myself?
A competent DIYer can, but most people should not. The install runs a fused power feed from the battery, a brake output to the trailer socket, and a mount that must sit clear of airbag deployment zones and your view of the road. Then the gain has to be set properly with the loaded van. An auto electrician or towbar fitter does these routinely, and if your car has a factory tow pack the wiring is often already pre-pinned.
The thresholds on this page come from the federal trailer brake design rule (ADR 38/05), the model Australian Light Vehicle Standards Rules as adopted by each state, and the states' own published towing guidance. It is general information, not advice about your specific rig: confirm weights against your van's compliance plate and check your state's current guidance before you tow.
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