What electric trailer brakes do and why they need adjustment
Electric trailer brakes use a magnet inside the brake drum to create stopping power when you press your tow vehicle's brake pedal. A signal travels from your vehicle through the brake controller to the trailer, telling that magnet to engage. Over time—usually every 12,000 to 15,000 miles of towing—the friction material inside the drum wears down, and the magnet has to work harder to stop the trailer. When the magnet sits too far from the drum, it cannot generate enough force, and your brakes become soft or unresponsive.
Adjustment brings the magnet closer to the drum so it can work efficiently again. This is not a repair; it is routine maintenance that keeps your brakes safe and prevents damage to the brake assembly. You can do this yourself with basic hand tools, though some people prefer to have a brake shop handle it.
Key Takeaways
- Electric trailer brakes need adjustment when the brake pedal feels soft, the trailer pulls to one side when braking, or you have not adjusted them in over a year of regular towing.
- The adjustment happens inside the brake drum and involves turning a star wheel to move the brake shoes closer to the magnet, which you can reach through a slot in the drum backing plate.
- You will need a brake spoon (a specialized tool with a hooked end), a jack and jack stands, and a way to spin the wheel while you work—either by hand or with the engine running in low gear.
- Each brake drum is adjusted separately, and you should check your trailer's manual for the exact backing plate layout because some trailers have the adjustment slot on the outside of the drum and others on the inside.
- If the brakes still feel soft after adjustment, or if you hear grinding or see fluid leaking, the friction material may be worn past the point of adjustment and the brake assembly may need replacement.
Tools and materials you will need
A brake spoon is the main tool—it has a hooked end that fits into the star wheel inside the drum. You can buy one at any auto parts store for $10 to $20, and it works on most electric trailer brakes. Some people use a flat screwdriver as a substitute, but a brake spoon is safer because it is designed to fit the wheel without slipping.
You will also need a jack and jack stands to lift the trailer safely. Never work under a trailer supported only by a jack. A lug wrench removes the wheel, and wheel chocks or blocks prevent the trailer from rolling. If you plan to spin the wheel while adjusting, you can either turn it by hand or have someone sit in the tow vehicle and put it in low gear while you work—this keeps the wheel spinning steadily without you having to crank it.
Wear safety glasses because brake dust will come out of the drum, and work gloves protect your hands from sharp edges inside the drum. Have a wire brush or old cloth nearby to wipe away dust so you can see the star wheel clearly.
Finding and accessing the adjustment mechanism
The star wheel sits inside the brake drum, and you reach it through a slot in the backing plate. On some trailers, this slot is on the outside of the drum (the side facing away from the trailer frame). On others, it is on the inside (the side facing the frame). Check your trailer's manual or look at the backing plate before you start—the slot is usually a rectangular opening about the size of your thumb.
Once you have located the slot, jack up the trailer, find it with jack stands, and remove the wheel. You will see the brake drum, which is the large metal cylinder. If the drum is stuck, spray the edge where it meets the hub with penetrating oil and wait 10 minutes, then tap it gently with a rubber mallet to break it loose. Do not hit it hard—you are loosening it, not damaging it.
Wipe away any dust or dirt around the slot so you can see inside. Shine a flashlight into the opening. You should see the star wheel, which looks like a small gear with teeth. It is connected to the brake shoes, and turning it moves those shoes closer to or farther from the magnet.
The adjustment process step by step
Insert the brake spoon into the slot and hook it onto one of the teeth of the star wheel. You are aiming to turn the wheel in the direction that moves the brake shoes toward the magnet—this is usually toward the bottom of the drum, but check your manual because direction varies by brake model. Spin the wheel by hand or have your helper keep the trailer wheel turning slowly.
Turn the star wheel in small increments—one or two teeth at a time. After each turn, try to spin the wheel by hand. You will feel resistance increase as the shoes move closer to the magnet. Keep adjusting until the wheel is hard to turn by hand, then back off one or two teeth so the wheel spins freely with light resistance. This is the correct adjustment point.
The goal is a light drag, not a locked wheel. If the wheel locks completely, you have gone too far and need to back off. Once you have the right feel, move to the next brake drum and repeat the process. Do all four drums (or however many your trailer has) so the braking force is even on both sides.
Testing your adjustment before towing
Reinstall the wheels and lower the trailer to the ground. Before you tow, test the brakes in a safe, empty area—a parking lot or quiet road works well. Tow at a slow speed and press the brake pedal. The trailer should stop smoothly without pulling to the left or right. The pedal should feel firm, not soft or spongy.
If one side still feels weak, that brake may need another adjustment. If the brakes feel good but you hear a grinding noise, the friction material may be worn through and the brake assembly may need replacement rather than adjustment. If the pedal is still soft after adjusting all four brakes, the brake controller in your tow vehicle may need checking—that is a separate issue beyond the trailer brakes themselves.
When to adjust and when to replace
Adjust your electric trailer brakes once a year if you tow regularly, or every 12,000 to 15,000 miles of towing, whichever comes first. Some people adjust them twice a year if they tow heavy loads or in mountainous terrain where brakes work harder. If you notice the brakes need adjustment more frequently than that—say, every few months—the friction material is wearing faster than normal, and you may be approaching the point where replacement is necessary.
Electric trailer brake friction material typically lasts 30,000 to 50,000 miles of towing before it wears out completely. Once it does, adjustment will not help because there is nothing left to move closer to the magnet. At that point, you will need to replace the brake assembly. A brake shop can tell you whether your brakes are worn out or straightforward need adjustment by inspecting the friction material thickness.
Frequently Asked Questions
How do I know if my electric trailer brakes need adjustment?
The brake pedal will feel soft or spongy, or the trailer will pull to one side when you brake. You may also notice the brakes do not stop the trailer as quickly as they used to. If you have not adjusted them in over a year of regular towing, they probably need it.
Can I adjust electric trailer brakes without removing the wheel?
Some trailers have the adjustment slot positioned so you can reach it without removing the wheel, but most require you to take the wheel off to access the star wheel safely. Removing the wheel gives you better visibility and makes it easier to spin the wheel while you adjust.
What if I turn the star wheel the wrong direction?
If you turn it the wrong way, the brake shoes move away from the magnet and the brakes become even softer. straightforward turn the wheel in the opposite direction until you feel resistance again. Check your trailer manual to confirm the correct direction before you start.
Do I need to adjust all four brakes at the same time?
Yes. If you adjust only one or two brakes, the trailer will pull to the side with the stronger brakes when you stop. Adjusting all four ensures even braking force across the trailer.
What does it mean if the brakes still feel soft after I adjust them?
The friction material may be worn too thin to adjust further, or the brake controller in your tow vehicle may not be sending a strong enough signal. A brake shop can inspect the friction thickness and test the controller to determine which is the problem.