What Electric Brake Adjustment Means and Why It Matters
Electric trailer brakes use a magnet that pulls a brake shoe against the drum when you press the tow vehicle's brake pedal. Over time, the brake shoe wears down and moves farther from the drum, so the magnet has to work harder to reach it. Adjusting the brakes means moving the brake shoe closer to the drum again, so the system works with less effort and stops your trailer more evenly.
You adjust electric brakes by turning a star wheel or adjusting bolt on the back of each brake assembly. The adjustment is small — usually a quarter turn at a time — but it makes the difference between brakes that respond when ready and brakes that feel soft or uneven. Most trailers have two brake assemblies (one per wheel on the axle), so you adjust both.
You do not need special tools for this job. A socket wrench, a brake adjustment tool (a flat-head screwdriver works), and a way to spin the wheel by hand are all you need. The whole process takes 30 to 45 minutes per axle.
Key Takeaways
- Electric brakes adjust by turning a star wheel on the back of each brake drum until the wheel becomes hard to spin by hand, then backing off a quarter turn.
- You must adjust both brake assemblies on the same axle equally, or your trailer will pull to one side when braking.
- The adjustment gets tighter as the brake shoe wears, so you may need to readjust every 12 to 24 months depending on how often you tow.
- If the brake still feels soft after adjustment, the problem may be a worn magnet coil or a low brake fluid level in the tow vehicle, not the shoe position.
Locate the Brake Adjustment Star Wheel
The star wheel sits on the back side of the brake drum, usually facing the ground. You may need to get under the trailer or turn the wheel so the access hole points toward you. Some trailers have a rubber plug covering the hole; peel or pry it out to see the star wheel inside.
The star wheel looks like a small gear with teeth. It has a slot on one side where you can fit a flat-head screwdriver or a brake adjustment tool. Turning it one way tightens the brake shoe against the drum; turning it the other way loosens it. The direction depends on which side of the axle you are on — the left and right wheels turn opposite directions, so check which way tightens before you start.
If you cannot find the access hole, check your trailer's manual or look for a second hole on the opposite side of the drum. Some older trailers have the adjustment on the inside of the wheel instead of the back of the drum.
Spin the Wheel and Tighten Until It Locks
Jack up the trailer so the wheel is off the ground and spins freely. Turn the star wheel with your screwdriver or adjustment tool, spinning it in the direction that tightens the brake. You will feel resistance increase as the brake shoe moves closer to the drum.
Keep turning until the wheel becomes hard to spin — you should not be able to turn it by hand without real effort. This is the point where the brake shoe is touching the drum. Stop there; do not force it or you risk bending the shoe.
Spin the wheel a few times to make sure it is truly locked, not just stiff. If it still spins, tighten another quarter turn and check again.
Back Off the Adjustment by One-Quarter Turn
Once the wheel is locked, turn the star wheel backward (the opposite direction) by exactly one-quarter turn. This creates a small gap between the brake shoe and the drum — about the thickness of a business card. That gap is necessary so the brakes do not drag and overheat when you are not braking.
Spin the wheel again. It should turn freely now, with no resistance. If it still feels tight, back off another quarter turn. The wheel should spin with almost no drag.
This one-quarter-turn gap is the standard for electric brakes. Too much gap and the brakes feel soft; too little and they drag. If you are unsure, err on the side of a little more gap — you can always tighten it again if the brakes feel weak.
Adjust the Second Brake Assembly the Same Way
Most trailers have two brake assemblies on the same axle (one per wheel). Adjust the second one using the exact same steps: tighten until locked, then back off one-quarter turn. The two adjustments must be equal, or your trailer will pull to the side that has tighter brakes when you stop.
If your trailer has two axles with brakes, repeat the process on the second axle. Some trailers have brakes only on the rear axle, but check your manual to be sure.
After you finish both assemblies, lower the trailer and spin each wheel by hand one more time to confirm they all turn freely and equally. If one wheel is noticeably harder to turn than the others, go back and adjust it again.
Test the Brakes Before Towing
Before you tow, test the brakes in a safe place — an empty parking lot or a quiet road where you can stop without traffic behind you. Tow the trailer at 10 to 15 miles per hour and explore the brakes gently. The trailer should stop smoothly without pulling left or right.
If the brakes feel weak or spongy, the problem is usually not the adjustment — it is more likely a worn magnet coil or a low brake fluid level in the tow vehicle. Check that the brake fluid in your tow vehicle is at the full line on the reservoir. If it is low, top it off and test again.
If the brakes feel strong and even, your adjustment is complete. If they still pull to one side, one brake assembly is tighter than the other. Go back and loosen the tight side by another quarter turn.
When to Readjust and What Wears Out
Electric brake shoes wear down over time, especially if you tow frequently or brake hard. As the shoe wears, it moves farther from the drum, and the brakes become softer. You may notice the brake pedal in your tow vehicle requires more pressure, or the trailer takes longer to stop.
Most trailers need readjustment every 12 to 24 months, depending on how much you tow. If you tow weekly, check the brakes every 6 months. If you tow a few times a year, once a year is usually enough.
If you find yourself adjusting the same brake assembly more than once a year, the brake shoe may be worn out and need replacement. Replacement is a bigger job that usually requires removing the drum and installing a new shoe, but it is worth doing before the shoe wears completely through.
Frequently Asked Questions
What if I cannot find the star wheel on my trailer?
Some older trailers use a different adjustment method — a bolt on the back of the brake assembly instead of a star wheel. Check your trailer manual for the exact location and direction. If you do not have the manual, contact the trailer manufacturer with your model number, and they can tell you where the adjustment is.
Do I need to adjust the brakes if they feel fine?
If the brakes feel responsive and your trailer stops evenly, you do not need to adjust them. However, checking them once a year is a good idea, especially before a long tow. Brakes that feel fine now may need adjustment in a few months as the shoe continues to wear.
What happens if I tighten the brakes too much?
If you tighten the brakes so much that the wheel locks and will not spin, you have gone too far. Back off a half turn and try again. Brakes that are too tight will drag, overheat, and wear out faster. They may also cause the tow vehicle's brake controller to overheat if it is working too hard to power the magnets.
Can I adjust the brakes while the trailer is on the ground?
You can, but it is harder and less accurate. Jacking up the trailer so the wheel spins freely makes it much easier to feel when the brake is locked and to spin the wheel evenly. If you must adjust on the ground, have someone spin the wheel while you turn the star wheel, or use a breaker bar to spin the wheel yourself.
Why do my brakes still feel soft after I adjusted them?
Soft brakes are usually caused by a worn magnet coil, not by the shoe position. The coil is the electromagnet that pulls the shoe against the drum. If it is worn out, it cannot pull hard enough no matter how close the shoe is. You may also have low brake fluid in the tow vehicle, which reduces the signal to the brake controller. Check the fluid level first, then have the magnet coil tested if the brakes are still weak.