INSTALLATION INSTRUCTIONS

DX20 Actuator (Formerly “Raptor” Model 20) for Trailer Brakes 20,000 lbs Capacity
#

TDE Part #

1A

70403-20K

1A

70403-20KD

1B

11286-BLK

1C

17028SA

2

70404K

3

70407K

4

70408K

5

48986A

6

50306

074-480-00 Safety Pin and Cable Assembly

7

50307K

K68-529-00

8

70409K

K74-571-00 Latch Kit

9

70405K

068-576-00

10

70406

068-560-00 Rear Cover

9
1

4

3

7

7
4

1A & 5

10

2
6

8
4

1C

1A

1B

2

READ AND UNDERSTAND THE ENTIRE INSTRUCTION/ASSEMBLY
PROCEDURE BEFORE INSTALLATION.
The DX20 works by the “surge” or “push” of the trailer toward the tow
vehicle. This automatically synchronizes the trailer brakes with the
brakes on the tow vehicle. When the trailer pushes against the tow
vehicle, the actuator telescopes together and applies the force to the
master cylinder, supplying hydraulic pressure to the brakes. The built
in sealed and independent dampening shock absorber controls the
telescoping shock against the hitch.
Be sure to comply with regulations for brakes in your state. Brake laws
sometimes are minimum standards and you may wish to add additional
brakes to your trailer to meet minimum Gross Vehicle Weight Ratings
(G.V.W.R.). Note: G.V.W.R. is the Gross Vehicle Weight Rating which
includes the trailer and the load weight as a Total Gross Weight.

Bolt the actuator to the tongue-using 5/8” diameter, 4” long grade
5 bolts. Attachment strength should equal or exceed 1-1/2 times
trailer G.V.W.R.

2.

Hydraulic brake lines should be installed on the trailer as described
in the installation manual supplied with the brakes. Note: Some disc
brakes require the use of flexible brake lines at the connection point
on the brake caliper. Follow brake manufacturer instructions.

3.

Use only DOT-3 brake fluid in the DX20 actuator. Use a pressure
type brake bleeder to bleed brakes. Follow manufacturer’s
directions. Or, manually bleed the brakes using directions on page 3.

4.

To bleed master cylinder and brakes, install bleeder hose on first
wheel cylinder to be bled; if tandem axle trailer, bleed farthest axle

©2019 Dexter Axle Company | www.dexteraxle.com

Description

Disc Brake DX20 Master Cylinder
K68-523-20 Kit: master cylinder, cap and 4
mounting screws
Drum Brake DX20 Master Cylinder
K68-523-00 Kit: master cylinder, cap and 4
mounting screws
Disc Brake Solenoid - used with
054-240-00
Disc brake actuators
Dampener Cylinder (each) 2
052-017-00
required
Wear Pad Kit: upper and lower
K68-540-00
wear pads
K68-532-00 Emergency Stop Lever and Spring
Actuator Pin Kit: 3 pins with
retainers and pin kit
Master Cylinder Cap with internal
068-572-00
bladder
K68-519-00

Emergency Stop Cable with
Connector Link
Emergency Stop Lever Cover and
Spring and 3 mounting screws

first, and the farthest brake on that axle first. Use a loose end of
hose from the bleeder valve submerged in a clear container of brake
fluid to observe bubbling (hose must be submerged into clean brake
fluid to keep air from traveling back into the brake cylinder). Loosen
the bleeder screw located in the wheel cylinder one turn; the system
is now open to the atmosphere. The bleeding operation for that brake
is complete when bubbling stops. Be sure to tighten bleeder screw
securely. Each wheel cylinder must be bled until all air is out of the
lines. Replenish the brake fluid during the bleeding process so the
level does not fall below half full level in the master cylinder reservoir.
When bleeding and testing is completed, make sure master cylinder
is filled to approximately 3/8” below the top of the reservoir and
filler cap is securely in place.

READ YOUR TOW VEHICLE OWNER’S MANUAL ON TOWING CAPACITY
AND OTHER TOWING RECOMMENDATIONS BEFORE INSTALLATION.
The DX20 Actuator is completely assembled and ready to bolt into
place (Tongue sizes: 3”x 4” & 3”x 5”, 9 ga. min.).
1.

DX Part #

-1-

5.

Road test trailer a short distance to activate the actuator several
times. Check fluid level again. Remember, low brake fluid levels will
result in reduced braking or no braking at all.

6.

When testing is completed, make sure master cylinder is filled to
approximately 3/8” below the top of the reservoir and filler cap is
securely in place. Road test again to make sure brakes work properly.

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RATED CAPACITY:
Maximum Actuator Capacity: 20,000 lbs. Gross Load; 2,000 lbs.
maximum tongue load; minimum tongue weight is 5% of G.V.W.R.

4.

Connect actuator breakaway cable carabiner to the tow vehicle
only. Do not connect to the safety cables or chains.

5.

The breakaway system is designed to only operate after complete
separation from the trailer or if the tongue goes under the rear of
the tow vehicle. The breakaway is not a parking brake. Do not use
as such. If the breakaway is accidentally applied while un-hitching,
insert a flat bladed screwdriver into the slot on either side of
the plastic cover on top of the actuator. The screwdriver blade
should go under the spring plate. Pry down on the handle of the
screwdriver to release the spring plate. The E-stop arm should fall
back and down when released.

The actual in-service rating is limited to that of the ball and hitch or
the least rated component on the tow vehicle or trailer being used or
the trailer manufacturer’s G.V.W.R. shown on the certification label,
whichever is lower (Note: G.V.W.R. is the Gross Vehicle Weight Rating
which includes the trailer and the load weight as a Total Gross Weight).
HITCHING TRAILER
1. The vehicle, towing hitch and ball must have a rating equal to or
greater than trailer G.V.W.R.

!

CAUTION

CAUTION

When resetting the break away system keep hands and fingers
clear as you reset the mechanism, hydraulic pressure held in the
system may cause the assembly to snap back suddenly.

• A loose fit between the coupler and hitch ball can cause the
actuator and hitch ball to separate, causing serious damage,
injury or death. Check coupler every time prior to towing and at
each stop on long trips. Always make certain that coupler latch
safety pin is securely installed into coupler latch.
• After reverse maneuvering, always insert coupler latch safety
pin back into coupler latch. FAILURE TO REMOVE SAFETY PIN
FROM REVERSE LOCK OUT POSITION HOLE WILL PREVENT
FORWARD MOVEMENT BREAKING THAT CAN RESULT IN
SERIOUS PROPERTY DAMAGE, INJURY OR DEATH.
2.

DX20 will accept 2-5/16” trailer hitch balls with a 20,000 lbs.
capacity only. Trailer balls larger than 2-5/16” or out of round will
not fit he coupler or may result in coupler failure. Balls smaller than
2-5/16” can cause shock loading and sudden disconnection. Make
certain ball latch is in correct position to retain the hitch ball. Push
latch lever down until safety latch engages the hitch ball. Always
insert safety pin into forward hole as a safety lock for the hitch ball
coupler prior to towing. Do not tow trailer if coupler is damaged.

3.

Connect safety cables or chains using crossed pattern under
tongue, or follow trailer manufacturer’s directions.

!

CAUTION

• A minimum of 5% tongue weight and a maximum 10% tongue
weight of the trailer GVWR must be positioned over the hitch
ball. The Trailer tongue should be parallel to the ground. Too
much weight can cause premature brake actuation and loss
of control of the towing vehicle. Too little tongue weight can
cause the trailer to fishtail, resulting in loss of control of the
tow vehicle and trailer (total trailer weight GVWR includes
weight of the trailer plus load).
• AVOID sharp turns, which can cause the actuator to bind
or jackknife against the tow vehicle or cause a bend in the
tongue. Either can damage the actuator causing brake failure.
AVOID towing trailer across large bumps or dips that may over
stress the connection between the trailer and tow vehicle, as
this could result in damage to the actuator.
• Failure to install the hitch pin before towing can result in
accidental opening of the coupler hitch latch which can lead to
the trailer coming off of the hitch ball causing serious damage,
injury or death. If pin will not fit into the latch hole, the coupler
is not attached properly. Reset coupler on hitch ball.

©2019 Dexter Axle Company | www.dexteraxle.com

6.

Any control devices that restrict operation of the actuator cannot
be used. This includes certain sway control devices. The actuator
must be free to telescope in response to braking requirements.

7.

Equalizing or weight distributing hitches may be used, allow six
to eight inches free chain length. DANGER: Tongue weight outside
rating limits will interfere with performance of actuator, and braking
system, and the tow vehicle.

8.

Automatic Free-Backing (backing-up without braking action) is
possible with this Actuator when supplied with an electrically operated
Reverse Lock-Out Solenoid or coupled with Free-Backing drum
brakes. To allow Free-Backing without either of those components
installed the Operator must manually Lock-Out the Actuator
movement while backing up. This is accomplished by placing a
7/16 X 5” long bolt (or comparable screwdriver) through the upper
hole provided through the actuator housing. DANGER: FAILURE TO
REMOVE THE BOLT/SCREWDRIVER AFTER BACKING WILL CAUSE
NO BRAKING ACTION IN NORMAL USE. REMEMBER TO ALWAYS
REMOVE THE BOLT/SCREWDRIVER AFTER BACKING THE TRAILER.

9.

Important: The supplied, cable
tethered, “Safety Pin” must be
installed in the Coupler Latch hole
(see illustration at right) during
towing at all times.

Safety Pin
Location

MAINTENANCE
1. Always check the brake fluid reservoir before using trailer. Make
sure it is at least half full. If not, refill to approx. 3/8” below the top
of the reservoir with DOT 3 brake fluid. Check for leaks and repair
as required. Never reuse brake fluid.

-2-

2.

To extend coupler and ball life, coat both with a thin coating of
grease. Wipe clean and renew grease film each time trailer is used.
A zerk fitting is installed on the coupler to make this step easier.

3.

Examine the actuator for bent parts or wear each time the trailer is
used. Replace parts as necessary.

4.

There are no user adjustments on the actuator.

5.

After excessive travel the brakes may need adjusted or bled, fluid
added to the reservoir, and connections checked for leaks. Adjust
per instructions found in brake installation manual. In general,
back off the adjusters on drum brakes from locked position, as
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required. Adjust Free-Backing brakes by rotating wheel in forward
direction only. Failure to adjust may result in loss of braking. Disc
brakes do not require adjustment, check for pad wear periodically.

!

5.

Insert the flat blade screwdriver in the Cable attachment loop, with
the blade of the screwdriver against the E-stop arm. Pull the handle
forward to pump the master cylinder (Fig. 5 & 6).

CAUTION

Figure 5

The exterior of the actuator and brakes should always be flushed
with fresh water after using trailer in corrosive conditions. This
includes salt water, fertilizers and other corrosive materials.
Before storing trailer remove brakes and clean thoroughly. It
is also wise to repack the bearings at the same time. Failure
to properly and adequately maintain the actuator could cause
serious damage, injury or death.

Figure 6

6.

Repeat several times and hold to build pressure to bleed each of the
brakes. Follow manufacturer’s instructions for bleeding the brakes.

While towing, if the actuator appears to be knocking against the
hitch ball while starting or stopping, check brake fluid reservoir and
fill if below 3/8” full from the top.

7.

Check the master cylinder reservoir often. Do not allow the
reservoir to empty. When bleeding is completed, fill reservoir to
within 3/8” from the bottom of the threads. DO NOT OVER FILL.

PLEASE NOTE THE FOLLOWING IMPORTANT INFORMATION ABOUT
MAINTAINING AND OPERATING THE ACTUATOR.
ƒƒ Actuator models designed for disc brakes do not have a check
valve installed. Check valves are required for use with drum brakes.
DO NOT use any actuator designed for drum brakes on a trailer
with disc brakes installed.

8.

Reassemble E-stop spring latch and cover (Fig. 7-11). Slide spring
catch back into position lining the holes in the plate with the holes in
the cover. Place plastic cover over the plate, apply Loctite® or thread
locker to threads and reinstall the 3 hex head screws.

6.

ƒƒ

Check all system components after breakaway system is used.
Replace any damaged parts with genuine Dexter parts only.

ƒƒ

DO NOT REUSE BRAKE FLUID. Always use fresh DOT 3 brake fluid
from a fresh container. Failure to maintain proper levels of fluid in the
reservoir will cause brake failure. Never use silicone based brake fluids.

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

BLEEDING THE BRAKES
Tools Required – a medium to large size flat blade screwdriver, a 3/16”
& a 5/32” hex key wrench, a wrench to fit the bleeder valves on your
brakes and brake fluid DOT 3. Do not use silicone brake fluids. This will
cause seal damage and void your warranty.
1.

Secure trailer on level ground. Chock wheels and/or attach trailer
to the tow vehicle to keep the trailer from moving during the
bleeding process

2.

Use the hex key wrenches to remove the 3 hex screws holding the
top black plastic cover on top of the actuator (Fig. 1 & 2).

Figure 1

Figure 2

9.

3.

Slide the rectangular metal E-stop spring catch backward several
inches (Fig. 3).

4.

Fill master cylinder reservoir with DOT 3 brake fluid. NEVER reuse
brake fluid. Use only new DOT 3 brake fluid. Never use silicone
based brake fluids (Fig. 4).
Figure 3

©2019 Dexter Axle Company | www.dexteraxle.com

Test brakes in a protected area such as a parking lot or side street.

EMERGENCY STOP CABLE OR E-STOP CABLE
The DX20 actuator is supplied with an emergency stop system that
applies the brakes in the unlikely situation were the trailer becomes
disconnected from the tow vehicle. The cable is PVC coated and coiled
for convenience. On one end the cable is connected to a lever arm on
top of the actuator. The other end of the cable has a hook to connect
to the tow vehicle. Should the trailer become disconnected from the
tow vehicle (both coupler and/or chains) the E-stop cable would pull
the lever and activate the master cylinder. A steel spring lock keeps the
pressure on the brakes until manually released.

Figure 4

-3-

1.

When towing the vehicle, connect the end of the E-stop cable
to the tow vehicle. Never connect the E-stop cable to the safety
chains or cables.

2.

Connection point should be a position on the tow vehicle that is
different from the safety cables or chains.

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WARNING: IT IS POSSIBLE THAT THE E-STOP CAN BE ACTIVATED BY
PULLING ON THE CABLE IN VARIOUS WAYS.
1. Forgetting to disconnect the E-stop cable from the tow vehicle and
pulling tow vehicle away from the trailer. This would pull the lever
and activate the brakes.
2.

Stepping on the E-stop cable with enough force to pull the lever
and activate the brakes.

3.

Attaching the E-stop hook in a way that is too tight and causes the
cable to be pulled when making turns while towing the trailer.

4.

Wrapping the E-stop cable around the actuator or trailer tongue
reducing the amount of free play in the cable.

5.

Leaving the E-stop cable dragging on the ground, causing the cable
to grab an object on the road.

RELEASING THE E-STOP
Always check the position of the E-stop lever to make sure it is not in a
locked position. Lever should be able to touch the rear of the slot in the
plastic cover when not activated.
1.

Figure 12 shows a released E-stop lever position. Figure 13 shows
an activated E-stop lever position.

Figure 12

2.

Figure 13

To release, use a flat bladed screwdriver to pry up the steel E-stop
spring (Fig. 14).
Figure 14

Place screwdriver
head under the
spring plate.
3.

Insert flat bladed screwdriver under the steel spring plate and push
the handle of the screwdriver down, prying the spring plate up to
release the E-stop lever (Fig. 15).
Figure 15

4.

E-stop lever should move freely after release (Fig. 16).

Figure 16

©2019 Dexter Axle Company | www.dexteraxle.com

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