This is a pretty easy, but time consuming process. Most of the time you will spend on this project is removing the old and rusted out gear and prepping the surfaces for the new disc brakes. The total time I spent on this project was about 6.5 hours, spending nearly 4 of those hours cutting the old brakes off of the trailer. This process can be shortened if you have a blow torch or plasma cutter instead of doing it the old fashioned way (My way below).
Necessary weapons:
Sawzall
Disc grinder with metal cutting discs (or other cutting device)
Extension cord
Large diameter wrench
Pliers
5lb sledge hammer
Heavy chisel
Prybar
Work gloves
Nitrile or Latex proctology gloves
Grease gun w/ marine grease
Bearing grease packer
Jackstands
3 ton jack
Assorted small wrenches
clear tubing 12inch- for bleeding brakes
DOT 3 brake fluid
1 pal to help pump the brakes and drive car
18 pack Coors Light or other
Step 1 is to make sure you have the trailer tires chalked. Nothing more humiliating than being run over by a parked boat (except maybe getting stuck in a hatch in 90 degree heat: see SaltyDawg for instructions).
Next is to crack a beer and then loosen the tire lug nuts. Jack the trailer up and place jack stands under the lifted side of the trailer, then remove the tire and set it aside. Lower the jack to “share” the trailer weight with the jack stands.
Grab the 5lb mallet and a short block of wood. Take the wood piece and place the wide end on the side of the bearing buddy. Use the mallet to gently tap the wood piece and “wiggle” the bearing buddy free from the hub assembly. Crush empty beer can with mallet (very entertaining!)
After removing the bearing buddy, use pliers to straighten the cotter pin and remove it. Next use a large crescent wrench to back the castle nut off of the hub and set aside. Verify that your beer is still full and the remaining soldiers have adequate ice. Wipe brow (or shiny, balding dome) as needed.
Here is where the fun begins (If anyone knows a short cut to do this, please chime in). Removing the old hub is normally done with brute strength, a pry bar, sawzall and grinder combination. I have yet to be lucky enough for the brake adjuster to function well enough to back off the brake tension, so I begin the process by pulling the hub out as far as I can and inserting a pry bar between the back plate and the drum.
After gaining enough clearance to see into the brakes, I use a sawzall to remove the top end brake shoe mount to relieve the brake pressure. I cut the brake shoe mounting bolt off and then pry the brake hub off of the axel.
Next, I use a grinder with a metal cutting head to remove the 4 back plate mounting bolts. Wear eye protection and some good ear muffs. You can also use a blow torch or plasma cutter to get the bolts off faster.
Cut off the old horizontal running brake line tubing, but make sure you have a catch bucket for leaking brake fluid once you cut the line. Verify that your new beer is still full and the remaining soldiers are safe
Once all of the old gear has been torn off, clean and prep the axel mounting surfaces for the disc brake mounting plate. Remove as much dirt and rust as possible and then pick up the installation instructions included with your new disc brakes.
Repeat this process for the brakes on the other side of the trailer.
After removing the old hubs, next I remove all of the old brake line cable and mounting fixtures all the way up to the actuator. Examine and clean out the brake fluid reservoir and remove all debris and old brake fluid. Verify that your newest beer is still full and the remaining soldiers are in a cool place. Place new order as required.
Next I started by installing the disc brake back plate, making sure that the mounting plate was mounted to allow the bleed values to point up, make sure to look for the “outside” stamp to mount the plate properly. Follow the manufacturers recommended torque settings for the back plate bolts.
I then prepare the new disc and bearings for installation by packing the bearings with marine grade lube using a grease gun and grease packer.
After inserting the greased bearing, I installed the bearing cover and gently tapped it into place using the mallet and small wood block. I then used the grease gun to fill grease completely over the bearings, while not contaminating the grease cover with excess grease. I stick the end of the grease gun into the space and fill to remove as much air as possible.
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Install a “spindo seal” kit spindle cover and gasket onto the spindle, and then install the disc/hub assembly over it. With the disc now on the spindle, I insert the grease gun tip into the hub space and fill in as much grease as I can. Once that space is filled with grease, I insert the outer bearing (already packed with grease), then the thrust washer, and then the castle nut.
Using a large crescent wrench, I slowly tighten the castle nut, while turning the disc. Once I feel resistance, I then back off the castle nut and ensure free motion of the disc. I insert the cotter pin thru the opening of the spindle and the castle nut and bend it over the spindle to secure it.
Tap the bearing buddy back on the hub and fill bearing buddy with grease using the grease gun. Make sure not to overfill the hub with grease as it will be forced out of the hub causing nasty grease spray when driving!
Slide the brake pad assembly into place over the disc and tighten the two mounting bolts to the manufacturers recommended torque setting. (Oops…forgot to take pics of this with the wheel off!)
Repeat process for the other brake assembly. You should be now finished with all liquid refreshments and seeking a sober and experienced trailer driver for upcoming “live” testing.
Remove all of the old brake lines all the way up to the actuator. Install new “flex line” tubing into both sets of the new brakes. Run the “short side” flex tube directly to the brake line junction connection and connect the stainless steel tubing to the far side flex line.
Install the flex tubing that will link the long brake line to the junction box and connect the pieces. If needed, coil up your extra slack stainless brake line by curling it around a large diameter pipe. Be careful not to kink the tubing!
Connect the new reverse disc brake sensor to the actuator and turn “hand tight” with appropriate wrench. Cut the old trailer harness off and install the new trailer wire pigtail that includes the “reverse” sensor to allow backing of the trailer. Make sure your connections are water tight as this is a critical connection that often gets douched with salt water.
Run the long stainless steel brake line from the brake line junction up to another flex line tube and connect it to the actuator sensor. The entire brake line system should now be assembled and ready to fill with brake fluid. Note the curly Q's I created to compensate for the additional SS tubing below.
Open the brake fluid reservoir and fill with the manufacturer recommended brake fluid (usually DOT 3) and leave the reservoir cap off. Next, grab your spare hitch receiver and insert it into the trailer hitch.
Go to the brake set that is furthest from the brake line junction and attach the 12 inch tubing to the top brake bleed valve.
Once the hose is attached, open the bleed valve with a small wrench and have your assistant plunge the hitch receiver to begin the flow of brake fluid through the brake line. Continue to fill the brake fluid reservoir with additional fluid as you are going through the brake fluid bleeding process.
Continue to compress the brake actuator with the hitch receiver until brake fluid begins to flow out of the bleeder hose and into your catch bucket. Continue this process until the flow of brake fluid is free of air bubbles and then close the bleed valve with "slow" plunging of the actuator to ensure good line pressure.
Move to the other brake set and repeat this same process until the flow of brake fluid is bubble free. As a final check, I repeat this process one additional time on each side until the brake actuator feels solid (not spongy) to the person pumping the actuator.
Put the trailer tires on and begin testing the brakes by hooking your tow vehicle to it as you normally would. Begin by testing the brake and trailer lights, and then move on to low speed testing. I start by moving the trailer a few feet forward and then quickly depressing the brakes/actuator before attempting to back the trailer into its original position.
the trailer passes the reverse and low speed tests, begin by taking the trailer for a neighborhood test ride to ensure all components are working correctly.
After ensuring all is functioning properly, also make sure that you check the trailer on the next few subsequent trips. Check for hubs that may need tightening after your initial few uses.
I think that covers it.
- True BD contribution. Thanks
FAG 
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