How Standard Electric Drum Brakes Work

The standard electric trailer brake is a drum brake assembly — a cast iron drum that rotates with the wheel, and two curved brake shoes lined with friction material inside it. When you apply the brakes, an electromagnet on the backing plate energizes and is pulled against the rotating drum. The drag from the magnet causes the shoes to wedge against the inside of the drum, slowing the wheel.

As the friction lining wears down, the shoes sit farther from the drum surface. This increases the gap the magnet has to bridge and reduces braking effectiveness. To compensate, you periodically turn the star wheel adjuster — a toothed wheel accessible through a rubber-plugged slot at the bottom of the backing plate — to push the shoes closer to the drum. This is the manual adjustment that every trailer owner with standard brakes needs to do.

How often depends on use, but most trailers with standard brakes need adjustment annually or every 3,000–5,000 miles. Under-adjusted brakes are one of the most common trailer brake problems in the field — they feel weak, need high controller gain, and put extra load on the magnet trying to compensate.

How Dexter Nev-R-Adjust Works

Dexter introduced the Nev-R-Adjust for 12" brakes in 2008 and 10" brakes in 2009. The underlying brake assembly is identical to the standard version. The difference is a 9-piece adjuster kit added to the backing plate — a cable attached to the brake shoe assembly, connected to a lever that engages the star wheel.

As the brake shoe moves when the brakes are applied, it pulls the cable, which rotates the lever, which advances the star wheel by one or a few teeth — automatically closing the gap created by shoe wear. According to Dexter's engineering team, the adjustment happens in both forward and reverse directions, but the increments are larger in reverse. Over time and many brake applications, the shoes are kept at or near the proper clearance without any manual intervention.

Side-by-Side Comparison

How to Tell Which Type You Have

You have two reliable ways to identify your brake type — one from outside, one from inside.

From Outside (Without Removing the Drum)

Look at the adjustment slot at the bottom of the backing plate. On a standard brake, you'll see the rubber plug covering the slot and nothing else. On a Nev-R-Adjust, you'll see the auto-adjust lever — a flat metal tab — partially visible through or adjacent to the slot. This lever is what prevents the star wheel from backing off and is what blocks access to back the adjustment off easily.

From Inside (With the Drum Removed)

This is the definitive check. Remove the hub and drum. On a standard brake, you'll see the two shoes, the magnet, the springs, and the star wheel adjuster — that's it. On a Nev-R-Adjust, you'll also see the adjuster cable running across the backing plate from the shoe to the adjuster lever. If you see a cable, it's Nev-R-Adjust.

By Part Number

If you can read the Dexter part number from the backing plate or the original paperwork:

Initial Adjustment — Nev-R-Adjust

Even though the Nev-R-Adjust self-adjusts in service, Dexter recommends an initial adjustment at installation. Without it, the shoes may be too far from the drum for the first few brake applications, and braking will feel weak until the auto-adjust catches up. Here's the recommended procedure:

1. Drive to a safe, level location

   Find a clear stretch of road or a large empty lot. You'll need room to accelerate to 25 mph and brake firmly several times.

2. Accelerate to 25 mph and use the manual override

   Use only the manual override button on your brake controller — not the tow vehicle's brake pedal. This applies only the trailer brakes. Apply them firmly but not so hard you skid.

3. Repeat 3–5 times

   Each application allows the adjuster to advance the star wheel. You should feel braking improvement with each pass. Allow the brakes to cool between hard applications.

4. Set controller gain

   Once braking feels solid, adjust your brake controller's gain setting for your load. On a proper initial adjustment, you should not need maximum gain to achieve effective braking.

Manual Adjustment — Standard Brakes

Standard brakes need periodic adjustment as the friction lining wears. Here's how to do it correctly:

1. Jack the trailer and support it safely

   The wheel must spin freely. Use proper jack stands — never work under a trailer supported only by a jack.

2. Remove the rubber plug from the adjustment slot

   The slot is at the bottom of the backing plate (6 o'clock position). Pull out the rubber plug and set it aside — you'll replace it when done to keep debris out.

3. Insert a brake spoon and turn the star wheel

   Insert a brake adjustment spoon (or a flathead screwdriver — a spoon works better) into the slot and engage the star wheel. Turn it to expand the shoes toward the drum. The direction depends on which side of the trailer you're on — on the driver's side, you typically turn the bottom of the wheel toward the rear of the trailer to expand. On the curb side, it's the opposite.

4. Adjust until the drum drags, then back off slightly

   Spin the drum by hand while adjusting. When you feel light drag against the shoes, stop — you're at or near correct. Back off 8–10 clicks so the drum spins freely with just a whisper of drag. This is the correct clearance.

5. Replace the rubber plug and repeat on all wheels

   Always adjust all wheels on the same axle (and ideally all axles) so braking force is even side-to-side.

Maintenance Schedule — Both Types

Which Should You Choose?

Both types are legitimate choices and millions of trailers run both successfully. The right answer depends on how you use your trailer:

Frequently Asked Questions