Adjusting “self-adjusting” electric trailer brakes isn’t always a hands-off process; while designed to maintain optimal performance automatically, these systems sometimes require manual intervention to ensure peak stopping power and safety. This guide provides a detailed walkthrough of the troubleshooting, testing, and, if necessary, manual adjustment processes to keep your trailer braking system in top condition.
Understanding Electric Trailer Brake Systems
Before diving into the adjustment process, it’s crucial to understand how electric trailer brakes work and the specific role of the self-adjusting mechanism. Electric trailer brakes use electromagnets to actuate the brake shoes against the drum. The amount of braking force is proportional to the electrical current sent from the tow vehicle’s brake controller.
The “self-adjusting” feature aims to automatically compensate for brake shoe wear. Typically, this involves a cable and ratchet mechanism that engages when the brakes are applied in reverse. When the shoes are worn, the cable pulls the ratchet arm, advancing the adjuster screw and bringing the brake shoes closer to the drum.
However, this system isn’t foolproof. Factors like improper installation, infrequent towing, heavy braking, or contamination can hinder the self-adjusting mechanism, requiring manual intervention.
Diagnosing Brake Issues: Is Adjustment Needed?
The first step is to determine if your brakes actually require adjustment. Here are some telltale signs:
- Reduced braking performance: The trailer takes longer to stop, or the tow vehicle has to work harder to slow down.
- Uneven braking: The trailer pulls to one side during braking. This indicates that one or more brakes are not functioning optimally.
- Brake noise: Squealing, grinding, or clicking noises can indicate worn brake shoes or a malfunctioning adjuster.
- High brake controller output: The brake controller consistently requires a high gain setting to achieve adequate braking, suggesting the trailer brakes are not contributing effectively.
- Pulling excessively hard on the breakaway cable This signifies the trailer’s brakes must be fully engaged to effectively slow the trailer, even when the tow vehicle is already braking.
Performing a Drag Test
A simple drag test can help assess brake performance. Find a safe, flat surface and slowly drive the trailer forward. Engage the brake controller manually, slowly increasing the gain until the trailer’s wheels begin to drag. Observe the point at which the wheels lock up. If the wheels lock up at a very low gain setting (e.g., 2 or 3), the brakes may be too tight. If a high gain setting (e.g., 7 or 8) is required, the brakes are likely too loose and require adjustment.
Another essential part of the diagnostic process is to visually inspect the brake components for wear, damage, or contamination.
Adjusting Electric Trailer Brakes: The Manual Process
If your diagnosis points to a need for adjustment, follow these steps:
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Safety First: Ensure the trailer is safely supported on jack stands. NEVER work under a trailer supported only by a jack. Chock the wheels on the opposite side of the trailer.
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Locate the Adjustment Slot: On the backing plate of each brake assembly, you’ll find an adjustment slot. It’s usually covered by a rubber plug. Remove the plug.
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Access the Adjuster Wheel: Use a brake adjustment tool (a specialized tool with a curved end designed to engage the star wheel) or a small flathead screwdriver. The adjuster wheel is a star-shaped wheel that, when rotated, expands or retracts the brake shoes.
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Tighten the Brakes: Insert the tool into the adjustment slot and turn the star wheel upward (usually) until the brake shoes make contact with the drum. You should feel resistance as you turn the wheel. Continue adjusting until the wheel is difficult to turn and the drum can barely be rotated by hand. The drum should be nearly locked.
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Back Off the Adjustment: Now, back off the adjuster wheel by turning it in the opposite direction (downward) 8-10 clicks. This allows the brake shoes to move freely when not engaged and prevents overheating.
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Test the Wheel Rotation: Rotate the drum by hand. It should spin freely with a slight drag. If the drum is still too tight, back off the adjuster wheel another click or two.
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Repeat for All Brakes: Repeat this process for each brake assembly on the trailer.
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Reinstall the Plugs: Replace the rubber plugs in the adjustment slots to prevent dirt and moisture from entering the brake assembly.
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Road Test: After adjusting all the brakes, perform a road test. Start slowly and gradually increase speed, testing the braking performance at different speeds. Pay attention to any pulling or uneven braking. Readjust if necessary.
Troubleshooting Common Issues
Sometimes, the adjustment process doesn’t go as smoothly as planned. Here are some common issues and how to address them:
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Frozen Adjuster Wheel: If the adjuster wheel is frozen, try spraying penetrating oil into the adjustment slot and letting it soak for a few hours. You may need to gently tap the backing plate with a hammer to help loosen the rust and corrosion. If this fails, you may need to disassemble the brake assembly for cleaning and repair.
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Stripped Adjuster Wheel: If the star wheel is stripped, it will need to be replaced. This requires disassembling the brake assembly.
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Worn Brake Shoes or Drums: If the brake shoes or drums are excessively worn, adjustment alone will not solve the problem. They must be replaced. Inspect them carefully during the adjustment process. Look for cracks, scoring, or excessive wear.
Frequently Asked Questions (FAQs)
Q1: How often should I adjust my self-adjusting electric trailer brakes?
While “self-adjusting,” these brakes should be inspected and tested at least annually or every 3,000 miles, whichever comes first. More frequent checks are recommended for heavy usage or harsh conditions.
Q2: Can I adjust the brakes without a brake adjustment tool?
Yes, but it’s not ideal. A small flathead screwdriver can be used carefully, but a brake adjustment tool provides better leverage and grip, reducing the risk of slipping and damaging the adjuster wheel.
Q3: What happens if I over-tighten the brakes?
Over-tightening the brakes will cause them to drag continuously, leading to overheating, premature wear of the brake shoes and drums, and reduced fuel economy for the tow vehicle.
Q4: What happens if I don’t tighten the brakes enough?
If the brakes are too loose, they won’t provide sufficient stopping power, increasing stopping distances and compromising safety. The brake controller will also have to work harder to compensate.
Q5: Why are my brakes squealing after adjustment?
Squealing can be caused by several factors, including new brake shoes bedding in, dust or debris on the brake surfaces, or glazed brake shoes. Sometimes, applying the brakes firmly several times can help resolve the issue. If the squealing persists, further inspection is required.
Q6: Can I adjust the brakes with the trailer tires on?
Technically, yes, but it’s strongly discouraged. Removing the wheels provides easier access to the adjustment slot and allows you to visually inspect the brake components more thoroughly.
Q7: What is the proper gain setting for my brake controller after adjusting the brakes?
There’s no one-size-fits-all gain setting. The ideal setting depends on the weight of the trailer, the load being carried, and road conditions. The goal is to set the gain high enough to provide sufficient braking without causing the trailer wheels to lock up. Start with a low setting and gradually increase it until you achieve optimal braking performance.
Q8: My trailer brakes worked fine before, but now they’re weak after sitting for a while. Why?
Rust and corrosion can form on the brake surfaces when the trailer sits unused, reducing braking performance. Applying the brakes firmly several times may help remove the rust. If the problem persists, the brakes may need to be disassembled for cleaning and lubrication.
Q9: Do I need to adjust my brakes after replacing the brake shoes or drums?
Yes, absolutely. After replacing the brake shoes or drums, you must adjust the brakes to ensure they are properly positioned and providing optimal stopping power.
Q10: How can I tell if my electric brake magnets are bad?
A simple continuity test with a multimeter can help determine if the magnets are functioning. A resistance reading that is significantly outside the manufacturer’s specifications indicates a faulty magnet.
Q11: Is it necessary to lubricate any parts during the adjustment process?
Yes, sparingly lubricating the adjuster screw threads with a high-temperature brake grease can help prevent corrosion and ensure smooth operation. Be careful not to get grease on the brake shoes or drums.
Q12: What are the potential dangers of improperly adjusted trailer brakes?
Improperly adjusted trailer brakes can lead to reduced braking performance, increased stopping distances, uneven braking, overheating, premature wear of brake components, and, most importantly, increased risk of accidents. A properly functioning and adjusted trailer brake system is crucial for safety.
By following these guidelines and performing regular maintenance, you can ensure that your “self-adjusting” electric trailer brakes provide safe and reliable performance for years to come. Remember, if you are uncomfortable performing any of these procedures, consult a qualified trailer mechanic.