INSTALLATION INSTRUCTIONS
Hat Style Disc Brake

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plate onto the existing axle brake flange, with bent legs of the
bracket facing out towards the axle wheel end. The adapter plate
mounts with five 3/8”-24 UNF bolts, nuts, and lock washers. Install
medium grade (blue) Loctite® 242 or equivalent on the threads
and torque the bolts/nuts evenly
Figure 2
in a star pattern to 35 ft. lbs..
Note: Some of the brake flange
adapter plates can be installed
with the (non-brake) hub still on
the spindle. If the hub must be
removed to install the adapter
plate, reinstall it with a new wheel
bearing seal, and with bearings
Brake
lubricated and adjusted per the
Flange Adapter Plate
axle manufacturer’s instructions.

CAUTION

• Failure to properly secure or support the trailer weight while
servicing could result in serious injury or death. Make certain all
lifting and supporting equipment has sufficient capacity, is used
properly, and the trailer is securely supported on jack stands.
• A “disc brake ready” actuator must be used with these brakes.
Actuators designed for drum brakes will cause disc brakes to
work improperly, quickly overheat, and fail, resulting in property
damage, serious injury, or death.
• Ensure the brake hydraulic system is properly bled and
functioning properly in order to assure adequate braking
performance for safe trailer operation.
• Ensure the caliper mounting fasteners and spindle nut are
tightened to the specifications below to avoid a caliper locking a
wheel, losing braking function, and/or loss of a wheel resulting
in a loss of control, property damage, injury or death.
1.

5.

Jack up trailer and secure on adequate capacity jack stands.
Follow trailer manufacturer’s recommendations for lifting and
supporting the unit. Use the jack only to lift the trailer, never for
support when servicing. Always fully support the trailer with jack
stands, all around; and block the trailer to keep it from rolling,
moving, or falling off the stands when being serviced.

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Figure 3

Figure 4

CAUTION

Do not lift or support the trailer on any part of the axle or
suspension system. Never go under any trailer unless it is
properly supported on jack stands which have been rated for
the load. Improperly supported vehicles can fall unexpectedly
and cause serious injury or death.
2.

Remove the tire and wheel assembly.

3.

Carefully inspect the original axle brake flange for straightness,
weld spatter and
Figure 1 Brake Flange
imperfections that will
affect proper mounting
of the brake caliper
or adapter plate later.
Address as necessary
(Fig. 1).

6.

For 3,500 lbs. disc brake kits, proceed to step 5. For 5,200 lbs. and
6,000 lbs. disc brake kits, proceed to step 4.
4.

Slide the hat rotor over the existing idler hub studs. Note: Use two
lug nuts to secure the rotor against the hubface when assembling
the calipers. After the caliper is installed, remove the lug nuts.
Check the length of the other studs protruding through the rotor
hubface and be sure they are proper lengths to work with the
existing trailer wheel and lug nuts (Fig. 3 & 4).

5,200 lbs. and 6,000 lbs. disc brakes kits will come with a brake
flange adapter plate (Fig. 2). Install the brake flange adapter

©2019 Dexter Axle Company | www.dexteraxle.com

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Inspect the caliper
Figure 5
ensuring that the brake
pads are properly
Adapter
installed. The brake pad
Mounting
friction material faces
Plate
towards the rotor and
seats into anchor points
and against the caliper
piston. Slide the caliper
over the rotor and attach
the caliper to the brake flange or brake flange adapter plate. The
caliper bleeder screw should be oriented to the top, and caliper
fluid inlet to the bottom. Typically the caliper will be mounted with
the caliper body/piston/brake lines towards the rear of the axle.
NOTE: If the original axle is a Dexter idler axle with a five lug hub, it
has a special hubface spacing, and so an L-shaped 3-hole spacer
is in the kit that will install between the new caliper and original axle
brake flange. The adapter is the unpainted part shown in Figure 5.
059-A34-00 | 2019.09

7.

Make sure the caliper bleeder screw (Fig. 6) is facing upward when
bolting on the caliper. Start the two
Figure 6
(5,200 lbs. – 6,000 lbs. kits) or
three (3,500 lbs. – 3,700 lbs. kits)
7/16”-20 UNF caliper bolts
through the brake flange or
adapter plate into the caliper yoke
with medium (blue) Loctite 242 or
equivalent. Install and torque the
bolts to 55 ft. lbs. Ensure the rotor
will rotate inside the installed
caliper with sufficient clearance
Bleeder
and no more than a slight contact
Screw
with the brake pads, or adjust
caliper/pad clearances as required
to allow rotor rotation.

8.

Use a brake hose with a male 3/16” inverted flare fitting to
connect to the caliper with enough flexibility to allow the caliper to
move at least a 1/2” as the brake pads wear. Tighten the brake
line fitting into the brass banjo inlet on the caliper just snug
enough not to leak. Reference torque: Only 6 to 7 ft. lbs. or finger
tight + 1/2 turn on the brake line. The 5/8” head “banjo” bolt
fitting is torqued to 30-35 ft. lbs.; no tighter or this hollow bolt may
strip. Connect and secure all brake lines appropriately for the
trailer’s intended use. Ensure that the caliper and brake inlet line
have sufficient clearance to the trailer frame and suspension to
avoid contact under any loading scenario. Fill the brake system
with new DOT 3 fluid (or if these are replacement brakes, a
different fluid may have been specified by the trailer manufacturer
in very rare cases; confirm compatible fluid for those) and bleed
per the brake actuator manufacturer’s instructions. Use a clear
bottle with hose at the caliper bleed ports so one can absolutely
verify all air bubbles are removed from the system when bleeding.

9.

Install the trailer wheel and Figure 7
ensure the wheel inside
has clearance to the brake
caliper body as it rotates.
Tighten all lug nuts in a star
pattern with an accurate
torque wrench to the torque
specified by the trailer
manufacturer (Fig. 7).

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CAUTION

Before road testing, make sure the area is clear of vehicular
and pedestrian traffic. Failure to brake safely could result in an
accident and personal injury to yourself and/or others.
Additional resources are available at www.dexteraxle.com.

CAUTION

When finished with the installation, torque the wheel nuts to the
trailer manufacturer’s specifications. Re-torque nuts again at 10,
25, and 50 miles to avoid a possible wheel separation, which can
result in property damage, serious injury, or death.
10. Re-torque the lug nuts again at 10, 25, and 50 miles to avoid a
possible wheel separation.
11. Road test the trailer in a safe location. After the first few stops,
check the brake fluid in the actuator reservoir and top off again
to the proper level. Note: brake performance may not be optimum
until the brake pads adjust and seat themselves to the rotor. If
braking performance still needs improvement, repeat the brake
bleeding procedure to resolve.
©2019 Dexter Axle Company | www.dexteraxle.com

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059-A34-00 | 2019.09