Ultimate Bass

Boat Trailer Disc Brake System Inspection

I recently performed a boat trailer disc brake system inspection on my Ranger Trail boat trailer. In an effort to help others save some money I took a lot of photos and have described each step of the process. Hopefully, with the photos, these instruction will be easy to follow. I do have access to a machine shop and performed a couple additional procedures simply because I had this access. While it’s best to have rotors turned and polished, if they are not damaged, simply cleaning and reinstalling is sufficient. If you have any questions please don’t hesitate to send me a message in the Ultimate Bass Forums.

Boat Trailer Disc Brake System Inspection

Boat Trailer Disc Brake System Inspection

1998 Ranger Trail D4600
VR-10 Disc Brake Caliper, pad and rotor removal Procedure

Tools/Materials Needed:
21mm or 13/16 wrench/Socket & Ratchet combo
1/2″ or 13mm Gear-wrench
1 – 3/8″ Allen head socket (1/2″ drive)
1/2″ drive impact wrench
Digital or Dial Caliper
Rotor (If Applicable)
Brake Pads (If Applicable)
Brake Clean Solvent 1 spray can

To get started, using a jack, raise the axle until the wheels are off the ground. Remove the center cap and wheel(s) and set them aside. Place a jack stand under the axle for stability and safety.
Using a 1/2″ wrench (I used a 13mm gear-wrench), loosen and remove the 2 brake caliper bolts.

Boat Trailer Disc Brake System Inspection

It may be necessary to loosen the top bolt all the way, but leave it in the caliper slide. On my brakes, there is not enough room to remove it due the close distance to the trailer frame.

On my calipers the bottom section has to be moved out away from the rotor first due to the top having “fingers” that lock in behind the caliper bracket.

Boat Trailer Disc Brake System Inspection

Slide the caliper bottom back and down just a little to clear the bracket assembly and inspect the caliper slides to make sure they are easy to move back and forth in each direction.

Boat Trailer Disc Brake System Inspection
Pay close attention to the rubber boots for dry rot or deterioration.

Boat Trailer Disc Brake System Inspection

Also inspect the rubber boot around the caliper piston for dry rot and deterioration.
The brake line to the caliper is a metal line rather than a rubber hose which can be easily damaged if care is not taken to keep the weight of the caliper off the line. In this instance I used a 12” length of metal coat hanger. Sliding one end through the caliper slide and hung the caliper to my inner fender/frame area. Normally, I would use a bungee cord for this, but there really wasn’t a way to secure it so this method worked great. Just make sure to keep the weight of the caliper off of the brake line or hose.

Boat Trailer Disc Brake System Inspection

The brake pads and the caliper bracket, along with the brake abutment clip are all removed as an assembly. Pay close attention to how the abutment clip is oriented to the bracket and pads (take photos and do one side at a time just in case).

Boat Trailer Disc Brake System Inspection
Using a 21mm or 13/16″ wrench or socket/ratchet assembly remove the 2 brake caliper bracket bolts (these bolts are extremely tight and it may take a breaker bar and socket in 1/2″ drive)
Once both bolts are removed, set the assembly down and remove the pads and clip from the caliper bracket.

Boat Trailer Disc Brake System Inspection

Inspect the brake pad friction surfaces for thickness, uneven wear, separation from the pad plates and pitting or holes in the surface material. Mine had some glazing and embedded rust that was transferred from the rotors so I lightly scuffed them to clean the surface with 180 grit sandpaper. The pad on the left has been cleaned up, and the one on the right hasn’t. Pads should be replaced when 1/16″ (0.060″) or less of pad friction material is left.

Boat Trailer Disc Brake System Inspection

 

Inspect the rotor for thickness, it must be replaced if it measures less than 0.882″ (22.4mm). Mine was well within specification so I removed the rotors from the hub assemblies and resurfaced them, the above measurement was after refinishing.

Boat Trailer Disc Brake System Inspection

Light surface rust is common on brake rotors due to sitting for extended periods of time (winter storage). Extremely thick, heavy rust on the rotor surface will cause premature wear, heat buildup and brake vibration. Brake vibration can be transferred through the tongue into the tow vehicle while applying the brakes especially on long downhill grades.

Remove the hub. For instructions see my article Cool Hub Removal and Inspection

Lug studs are used to bolt the rotor to the hub assembly. To remove the rotor for replacement or refinishing, spray the five lug studs with a good penetrating oil.

Boat Trailer Disc Brake System Inspection

 

Boat Trailer Disc Brake System Inspection

These are 3/8 Allen head bolts and they are extremely tight! I had to use a 1/2″ drive impact wrench that delivers 1,190 ft. lb. of Bolt Break Away Torque. Also had to use a 1/2′ to 3/8″ reducer since I don’t have a 1/2′ drive 3/8 Allen socket!  As far as I can tell there is no way a person could break these bolts loose by hand while trying to hold the rotor. Realistically, I could have resurfaced the rotors with the hubs still bolted on, but chose to separate them to document the process. Separating the rotor and hub would be necessary if someone had to replace the rotors with new ones. Separation would also be necessary to completely strip everything down and repaint all the components for a cleaner look.

Once they broke free I had to run them in and out slowly while spraying penetrating oil on the stud side so I didn’t damage the threads.

Boat Trailer Disc Brake System Inspection

Be patient and use plenty of lubricant, eventually the two will separate.

Boat Trailer Disc Brake System Inspection

Chucking them up in the brake lathe and taking a couple quick cuts with new bits cleaned them up.

Boat Trailer Disc Brake System Inspection

I then buffed the surface to create the best brake coefficient surface possible.

Boat Trailer Disc Brake System Inspection
Clean everything up with brake cleaner solvent or soapy water and it’s time for reassembly and installation.

All the mating surfaces should be free of rust, lay the rotor over top of the hub and install the 5 Bolts. I torqued mine to 100 ft. lbs.
Please follow this link for bearing, seal and rotor installation and adjustment procedure Cool Hub Removal and Inspection

Inspect the Brake Caliper Bracket for rust, pitting or wear marks. These will cause the pads not to slide freely on to the bracket. If rust is present, clean the surfaces to remove the rust and apply a small film of lubricant to the contact areas. Here is mine all cleaned up.
Boat Trailer Disc Brake System Inspection

Make sure no lubricant gets on the brake pads or rotor contact surfaces. Install the pads and abutment clip to the bracket.

Boat Trailer Disc Brake System Inspection
Slide the bracket and pads over the rotor and install the two bracket bolts, torque to 50 ft. lb.

Install the brake caliper making sure to get those locking “fingers” in place on the top. (see earlier removal procedure)

Boat Trailer Disc Brake System Inspection

Torque the two caliper bolts to 17ft. lb. This is all it takes to inspect a trailers brake pads and rotors. Thank you for reading, and I hope this helps you save some money when it comes to trailer maintenance. If this helped, please share it with other boat owners.

Banjo Pickin Bass Hunter!
Rick Olson



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