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Trailer Maintenace
How do I adjust my drum brakes on a boat trailer?
Types of Hydraulic Drum Brakes
When it comes to boat trailers, there are two main types of hydraulic drum brakes: Uni-Servo and Duo-Servo.
- Uni-Servo Drum Brakes
- Use a single-acting wheel cylinder.
- The primary shoe pushes against the drum, which then moves the secondary shoe through the adjuster.
- Braking in reverse is significantly less effective compared to forward braking.
- This type is commonly used on trailers with a surge hitch system. Venture Trailers, when drum brakes were standard, used uni-servo brakes.
- Duo-Servo Drum Brakes
- Use a dual-piston wheel cylinder.
- Both primary and secondary shoes are pushed into the drum, creating more braking force.
- Provide stronger braking in both forward and reverse.
- Typically found in electric/hydraulic or heavy-duty applications.
⚠️ Note for Venture trailer owners: Venture has since transitioned to disc brakes as standard on most models, but if you own an older Venture trailer with drums, it’s most likely equipped with uni-servo brakes.
Step-by-Step Drum Brake Adjustment
- Elevate the Wheel
- Safely jack up the trailer and secure it with jack stands.
- Locate the Adjuster
- On the back of the brake assembly, remove the rubber plug at the 6 o’clock position on the backing plate. This gives you access to the brake shoe adjuster.
- Tighten the Adjuster
- Rotate the wheel forward (same direction as trailer travel).
- Using a brake spoon or screwdriver, turn the adjuster until the wheel locks and can no longer be spun by hand.
- Back Off the Adjuster
- Release adjuster tension until the wheel spins one full revolution after giving it a firm hand spin.
- Repeat for Each Wheel
- Perform this adjustment on every trailer wheel equipped with drum brakes.
Why Adjustment Matters
- Keeps braking force balanced across all wheels
- Prevents uneven wear of brake shoes
- Reduces risk of premature lock-up or weak braking
- Essential for safe, controlled stopping — especially with heavy boats