Trailer Brake Controllers: Proportional vs Time-Delay, and How to Set One Up
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If your trailer has electric brakes, a brake controller is what makes them work. It sits in the cab, reads your braking and sends power to the trailer's brakes through the 7-way connector.
Do you need one?
- Electric trailer brakes: yes. Electric brakes don't work without a controller.
- Surge (hydraulic) brakes: no. Surge brakes activate on their own as the trailer pushes against the hitch; they're common on boat trailers.
- No trailer brakes: check whether your trailer legally needs them. The weight limit differs by province — see trailer brake requirements in Canada.
Proportional vs time-delay
| Time-delay | Proportional (inertia-based) | |
|---|---|---|
| How it works | Ramps up braking power over a set time after you press the pedal | An accelerometer senses how hard you're stopping and matches trailer braking to it |
| Feel | Less precise; can feel grabby or late | Smoother stops that track your braking |
| Hills | Same output regardless of grade | Adjusts automatically — less power uphill, more downhill |
| Best for | Occasional towing, lighter trailers | Frequent towing, heavier trailers, mountain driving |
How to set up a brake controller
Follow your controller's instructions — these are the general steps CURT describes:
- Connect the trailer on level ground in a safe, open area.
- Let it calibrate. Most modern controllers level themselves; watch for the indicator.
- Set the output (gain). Gain is how much power goes to the trailer brakes. At about 40 km/h (25 mph), brake firmly. If the stop feels sluggish, increase gain; if the trailer wheels lock, reduce it.
- Adjust sensitivity or boost with similar low-speed tests until braking starts neither too late nor too abruptly.
- Re-check whenever the load changes. A loaded trailer needs more gain than an empty one.
The manual override lever
Every controller has a manual control that applies the trailer brakes without the tow vehicle's brakes. Use it to slow gently on long descents and to straighten a swaying trailer — see how to prevent and stop trailer sway.
Wiring it in
Many trucks have a factory plug under the dash, so a vehicle-specific harness connects the controller with no splicing. You also need a working 7-way connector at the back — see 4-pin vs 7-pin wiring.
Browse brake controllers and breakaway systems.
Setup steps: CURT — How to use a trailer brake controller, checked September 2026.