Upgrade Your Trailer To Disc Brakes

Instead of spending money fixing drum brakes, upgrade them to discs.

Like many boat trailers, mine had hydraulic drum brakes, but after a couple of trips to the coast, I noticed they didn’t engage like they should. When I attempted to adjust them, I discovered the drum’s brake adjuster was rusted solid. Instead of repairing them, I decided to upgrade to disc brakes that don’t need adjusting. In addition to superior braking, disc brake pads are also much easier to replace.

Before you shop for new brakes, check to see if you have a four- or five-hole trailer axle brake mounting flange. I decided to purchase the Kodiak 12-inch Dacromet and Stainless Steel Vented Integral Rotor/Hub kit, which also included new bearings and seals. Because I had drum brakes, I needed to change my surge brake actuator to one that would accommodate the higher pressure required for disc brakes. I have a Titan Model 10 actuator and after some searching I found I was able to purchase a new master cylinder instead of having to replace the entire actuator, which saved me more than $300 and was a viable option because the rest of the actuator was in great shape.

I also needed to get an electric reversing solenoid, since my drum brakes were free-backing, meaning I could back up without a solenoid. This solenoid allows me to back the trailer by preventing the fluid from pressurizing the brake lines.

First, chock the wheels or connect the trailer to its tow vehicle to ensure it doesn’t move, then jack up the boat trailer and remove the wheels, hubs, hydraulic brake lines and existing brake system (1).

Inspect the axle spindle to ensure it is in good shape (2). If it has surface rust, use 220-grit sandpaper to make it smooth again and give it a good cleaning with brake parts cleaner, to get it ready for new bearings. If it shows anything more than minor surface rust, you should consider replacing the axle. Now is a good time to check that the grease fittings are working properly and not clogged or rusted; inject some grease with a grease gun and see if it comes out of the grease hole.

Next, install the caliper mounting bracket (3). Mount the left-side caliper in the 3 o’clock position and install the right-side caliper in the 9 o’clock position. Torque the bolts according to your axle manufacturer’s recommendations.

Time now to mount the one-piece hub and rotor assembly. After packing the seals and bearings with grease, I fitted them into the hub/rotor and then installed the hub/rotor on the axle (4). Make sure to wipe down the rotor with a rag that’s been sprayed with brake cleaner, to remove any grease that may have gotten on the rotor’s surface.

The next step is to install the caliper onto the mounting bracket and rotor (5), with the bleeder screw pointing up. I torqued the caliper guide bolts to 45 foot-pounds and then attached the brake lines to the caliper (6).

The most difficult part of the installation is to bleed the brakes, which is critical to make the brakes work properly. It can be done manually or with a pressure bleeder, which can be purchased at a local auto parts store. Manually bleeding the brakes is a two-person job, because someone has to “pump” the breakaway lever on the actuator while another person opens the bleeder screw to allow the air bubbles to bleed out of the lines and calipers. It’s a good idea to re-bleed the system after your first tow, just in case there was an air bubble that dislodged during the trip.

Now you can reinstall the wheels, according to torque specs for your axle/ wheel. It’s a good idea to recheck the lug nuts after your first trip.

The final step is wiring the reversing solenoid (7). On my trailer, I had to swap the four-way plug for a seven-way plug. Then I ran the left/right turn, stop and taillight wires to the appropriate locations on the new plug. For the reversing solenoid, I ran the hot wire to the reverse wire on the plug, then installed the other wire to the trailer’s ground. To check that the solenoid is working properly, have someone press the brake pedal on your tow vehicle. You should hear a faint click, which is the solenoid closing, which will allow you to back the trailer when you’re in reverse.

During every tow, at every stop, check to ensure the hubs are within normal operating range (130 to 175 degrees Fahrenheit), which can be accomplished with a cheap thermal scanner from any parts store. If the hubs are hotter than that, you may have a bad bearing or may need to re-grease the hubs.


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