Trailer Brake Controllers
How to Adjust Trailer Brake Gain
Gain is not a number you look up. You set it empirically, and you reset it whenever the load changes.
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Short answer
In an empty parking lot, roll at about 25 mph and apply the controller's manual override alone - not the brake pedal. Raise the gain until the trailer brakes firmly without locking its wheels, then back off slightly.
The procedure
Five minutes, loaded as you will tow
Find a clear, flat, empty surface
An empty parking lot or a quiet straight road. You need room to do this a few times without traffic.
Start low
Set the gain to a low value. You are going to raise it, which is safer than starting high and locking the trailer's wheels.
Roll at about 25 mph
Steady speed, straight line, hands on the wheel.
Apply the manual override only
The lever or slider on the controller. Do not touch the brake pedal - you are testing the trailer's brakes in isolation.
Feel what happens
Too low and you barely notice anything. Correct and you feel the trailer pulling the rig back firmly and smoothly. Too high and the trailer's wheels lock and skip.
Raise the gain a step and repeat
Keep going until you reach the point just before lock-up, then back off one step.
Confirm with the pedal
Now brake normally. The rig should slow as one vehicle - no feeling of the trailer pushing, no feeling of it dragging.
Reading the symptoms while towing
| Symptom | Meaning | Action |
|---|---|---|
| Trailer shoves the truck under braking | Gain too low | Raise it |
| Jerky, grabby stops at low speed | Gain too high | Lower it |
| Trailer wheels lock on a damp surface | Gain too high for conditions | Lower it; reset when dry |
| No trailer braking at all | Wiring or connection fault | Check the 7-way and the ground, not the gain |
| Needs a very high gain to do anything | Worn magnets or shoes | Inspect the trailer brakes |
When to reset it
- Any significant load change. A loaded trailer needs more gain than an empty one. This is the most-missed reset.
- A different trailer. Obviously - and this is the argument for a controller with stored settings.
- Wet or loose surfaces. Lower gain avoids locking the trailer's wheels.
- After brake service. New shoes and magnets change the response.
- At the start of each season. Brakes that have sat all winter behave differently.
Quick picks
Tap any row to jump to the full write-up. How these are chosen - and what we do and do not claim to know - is published in full on our research methodology page.
| # | Product | Best for | Our read | Price |
|---|---|---|---|---|
| 1 |  Tekonsha Prodigy P3 Trailer Brake Controller Remembers per trailer | Towing more than one trailer | Stored settings prevent wrong-gain departures | Check price on Amazon #ad Affiliate link - we publish no price; Amazon shows the current one |
| 2 |  CURT Spectrum Integrated Proportional Brake Controller Readable at a glance | Multi-axle trailers | Tri-color LED state indication | Check price on Amazon #ad Affiliate link - we publish no price; Amazon shows the current one |
| 3 |  Tekonsha Primus IQ Trailer Brake Controller Simplest to set | One truck, one trailer | One adjustment, nothing else to configure | Check price on Amazon #ad Affiliate link - we publish no price; Amazon shows the current one |
1. Remembers per trailer
Tekonsha Prodigy P3 Trailer Brake Controller
Tekonsha · Best for towing more than one trailer
The proportional controller most other proportional controllers get measured against. It stores settings per trailer, reads out what it is actually doing, and diagnoses wiring faults on the screen instead of leaving you guessing at the connector.
We have not sourced a full specification table for this model from the manufacturer’s own site at a stable address. Rather than repeat figures we cannot cite, the assessment above is limited to what the design and the maker’s published description genuinely establish.
What works
- Stores separate settings for multiple trailers, so you are not re-dialing gain every trip
- On-screen diagnostics name the fault instead of just refusing to work
- Boost settings let you bias braking toward the trailer on a heavy load
What does not
- Needs a proper mounting location within reach and sight of the driver
- More controller than a single light trailer ever needs
Skip it if
Overkill if you tow one small trailer a few times a year and never change the load - a simpler proportional unit does the same job on that trip.
#ad Affiliate link - we publish no price; Amazon shows the current one
2. Readable at a glance
CURT Spectrum Integrated Proportional Brake Controller
CURT · Best for multi-axle trailers
A hardwired proportional controller with tri-axis sensing, a tri-color LED readout and a wide axle range - up to four braked axles, or eight with the right wiring. Mounts at essentially any angle, which solves the main problem of fitting a controller to a modern dash.
Published specifications
What works
- Mounting angle is a non-issue, which widens the list of places it will fit
- Covers heavier multi-axle trailers that a basic controller will not
- LED color tells you the state at a glance without reading a number
What does not
- An LED is a far coarser diagnostic than a text display
- Still a hardwiring job with a vehicle-specific harness
Skip it if
Skip it if you want to read exact output voltage while you tow - the color band is deliberately simpler than that.
#ad Affiliate link - we publish no price; Amazon shows the current one
Raw specifications: CURT’s own page. We earn nothing on that link.
3. Simplest to set
Tekonsha Primus IQ Trailer Brake Controller
Tekonsha · Best for one truck, one trailer
Proportional braking without the memory, the boost profiles or the big display. For one truck and one trailer, that subtraction costs you almost nothing in how the rig actually stops, which is why it stays the default recommendation for a first controller.
We have not sourced a full specification table for this model from the manufacturer’s own site at a stable address. Rather than repeat figures we cannot cite, the assessment above is limited to what the design and the maker’s published description genuinely establish.
What works
- Proportional response at a far lower price than a flagship controller
- Small enough to mount where a larger unit will not fit
- Mounts at a range of angles without needing to be level
What does not
- No per-trailer memory, so a second trailer means re-setting gain each time
- Display tells you much less when something is wrong
Skip it if
Not the one if you swap between a light utility trailer and a heavy camper - without stored settings you will eventually drive off on the wrong gain.
#ad Affiliate link - we publish no price; Amazon shows the current one
Key takeaways
- Set gain empirically at about 25 mph with the manual override alone.
- Aim for firm braking just short of lock-up, then back off a step.
- A trailer that shoves the truck is under-braked; jerky stops mean over-braked.
- Reset after any meaningful load change - this is the step people skip.
How we sourced this
Every figure on this page came from one of the following, each fetched while the page was written. Where a manufacturer or regulator does not publish a number, we say so rather than estimate it.
Common questions
- What gain setting should I use?
- There is no universal number. It depends on trailer weight, brake condition and the controller's scale. The parking lot procedure takes five minutes and gives you the right answer for your rig.
- Should the trailer brake before or with the tow vehicle?
- With it, or very slightly ahead. A trailer braking slightly ahead keeps the rig in tension, which is stabilizing. A trailer braking behind pushes the tow vehicle.
- Is it bad to tow with the gain too high?
- It wears trailer brakes faster, makes low-speed stops unpleasant, and risks locking the trailer's wheels on a slippery surface - which removes their grip entirely.
More in Trailer Brake Controllers
If the trailer has electric brakes, something has to tell them how hard to work. That something is a controller, and how you set it decides how the rig stops.
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Found something out of date, or a figure you can source better than we did? Corrections get read first. How we research explains how these pages are put together, and contact is one click away.