Standard Air Chamber
Mounting Brackets
“S” Cam

Corrosion
Resistant Bolts

Shoe Roller

Caliper and
Brake Pads

Brake Shoes

Service Air Chambers

Forged Spider

Hi-Performance
Truck-Type
Brake Blocks

Disc Rotor

Anchor Pins

Specifying Axles
The axle capacity is usually determined by subtracting the hitch load from the Gross Vehicle Weight. The remainder
will be the load to be carried by the axle(s). When making this calculation, be sure to consider the final load
distribution. If the weight is shifted off-center laterally, the load imposed on the wheel(s) on the side closest to the
load center will be greater. The load on the heavier side must not exceed one half the rated capacity of the axle(s).
Torflex® axles should be specified in such a way that will position the vertical section of their mounting brackets
directly under the most rigid section of the frame members. This will help to ensure proper support of the axle
brackets (see illustrations in the Torflex® Installation section).
For applications requiring lower floor or frame heights, drop spindle axles as well as underslung springs on straight
spindle axles can be used to achieve the desired height. When Torflex® axles are called for, the starting angle of the
torsion arm can be specified to be above the horizontal plane to accomplish the same results.
Leaf spring type axles must have sufficient clearance to the frame to operate properly (see Bump Clearance
definition). If the spring hangers are too short, the axle may contact the frame during articulation of the suspension
and result in overloading of the axle and possible damage. If the spring hangers are too long and provide too much
clearance, the springs may be damaged if excessive loads are encountered and the axle is allowed to move too
much. If this condition exists, bump stops should be used to prevent over travel.

10

Other Trailer Components
Brake Actuation Systems
Electric brake controllers – These devices are used to supply a variable voltage to the electric brakes. The inertial
type controller relies on a pendulum or an accelerometer to sense deceleration of the vehicle when the stop light
circuit is activated. Hydraulic/electric controllers are tapped into the tow vehicles hydraulic brake lines and sense
the pressure in the system when the brakes are applied. A third method of electric brake actuation is the electronic
controller that employs a timing device. Triggered by the stop light circuit when the brakes are applied, the controller
begins sending a pre-programmed voltage to the trailer brakes. The output can be tailored to ramp up over a
prescribed time period and must be synchronized to the rate of deceleration desired.
Electric/hydraulic actuator – Hydraulic brake system actuator that supplies brake fluid pressure to the trailer’s
hydraulic brakes. The actuator output pressure is proportional to the brake control signal received from a suitable
electronic brake controller.
Vacuum boost/hydraulic actuators – Used to control hydraulic brakes, this type actuator operates a hydraulic
master cylinder with a vacuum chamber synchronized to the towing vehicle brake system. These systems are
typically used on tag axles for motor homes and equipment trailers where the tow vehicle is not equipped with air
brakes.
Air boost/hydraulic actuators – Systems of this type are used for equipment and utility type trailers towed by
air brake equipped vehicles. The booster is an air cylinder which operates the master cylinder. Braking force is
modulated by controlling the air pressure to the booster.
Hydraulic surge coupler – A surge coupler serves a dual function by providing the means for connecting the trailer
to the tow vehicle as well as actuating the trailer brakes. A master cylinder is built into the coupler and is operated by
the over-running force of the trailer against the tow vehicle. Note: For surge couplers used with disc brakes or nonfree backing drum brakes, it is recommended to have a backup solenoid on your surge coupler.

Hitches
Ball and coupler – Classified by SAE for trailers divided into gross weight categories, this hitch type uses a ball
attached to the tow vehicle and a corresponding socket or coupler affixed to the tongue of the trailer.
Class 1 – trailers up to 2000 lbs. GVW
Class 2 – trailers over 2000 lbs. up to 3500 lbs. GVW
Class 3 – trailers over 3500 lbs. up to 5000 lbs. GVW
Class 4 – trailers over 5000 lbs. up to 10,000 lbs. GVW
Pintle hook and lunette eye – A pintle hook is a device which incorporates a latching mechanism to prevent
unwanted disconnection of the trailer. The hook shaped part of the system is attached to the towing vehicle and the
trailer tongue is fitted with a ring, sometimes called a tow bar eye or lunette eye. SAE lists two Application types of
these devices.
Application Type I – used where the vertical hitch load does not exceed 5% of the towed vehicle weight.
Ap­plication Type II – used for vertical hitch loads greater than 5% but not exceeding 20% of the towed
vehicle weight.
Fifth wheel hitch – For this type of hitch, the tractor or tow vehicle will be outfitted with a mechanism called the fifth
wheel. The mating component affixed to the trailer is called the king pin. The load bearing capability of the fifth wheel
hitch is normally higher than the ball type hitch. Because the hitch point is located over or slightly forward of the tow
vehicles rear axle, the system can carry a greater portion of the trailer weight.
Gooseneck hitch – Similar in nature to the fifth wheel hitch, this type connects to the tow vehicle using a modified
form of the ball and coupler concept. The ball portion may be mounted on a plate attached to the tow vehicle and the
coupler on the gooseneck of the trailer or these two components can be reversed with the ball on the gooseneck and
the inverted coupler attached to the tow vehicle. Both methods are used and offer the weight bearing advantage of
the fifth wheel type hitch.

11

Installation Suggestions
Dexter Axle offers a variety of suspension types and associated components to be used for the attachment of trailer
running gear. It is of vital importance that the installer be familiar with the axles' features and characteristics so that
they may be oriented correctly at installation. All Dexter axles are directional by nature, that is they must be installed
with the front of the axle facing forward and the top facing upward. Attention to this important detail will ensure
optimum performance from both the brake and suspension systems.

Hanger Welding Specifications for Leaf Spring Axles

(REAR HANGER FOR SINGLE AXLE APPLICATION)

CAUTION!
Undercutting can result in weakened
components and lead to premature failure.

Installation Procedures for Leaf Spring Axles
Most trailer manufacturers have developed their own techniques for the installation of running gear. The sequence
that the components are installed is not so important as long as it suits your particular production flow. However,
it is essential that these components be attached to the vehicle frame in the proper manner to ensure trouble free
performance. Spring eyes and equalizers must be free to rotate. Binding can lead to unsatisfactory ride performance
and possible spring failure.

12

Installation Suggestions

CAUTION
• Over tightening the nuts can lead to fastener failure. The torque
specification for the ⁷⁄₁₆"-20 hex nut used on shouldered shackle
bolts is 30 to 50 Ft. Lbs.
• The nut should not be used to “pull” the shackle bolt into the
hanger. Instead, the bolt should be driven into place to allow the
serrations to grip the hanger.
• Using an impact wrench without some type of torque limiting device
can damage the threads and the serrations.
• Shackle bolts that are free to rotate will severely limit the service life
of the hangers.

Torflex® Axle Installation Procedure
The following instructions describe methods that can be used to attach your Torflex® axles to the vehicle frame.
Step 1: The user must first decide where to place the axle(s) on the trailer. The position of the wheel center relative
to the CG (center of gravity) will determine the final axle loading as well as the hitch load.
Step 2: Determine the method of attachment you wish to use. For structural tube type frame rails, refer to Figure A
for the recommended attachment. For 'C' channel or 'I' beam type frame, refer to Figure B.
Step 3: Once the method of attachment is decided, the axle(s) must be carefully aligned on the trailer frame. The
axle(s) centerline must be perpendicular to the longitudinal centerline of the trailer. See Figure C.
NOTE: Misalignment of the axle(s) can cause poor tracking and accelerated tire wear.
Attachment To Structural Tube Type Frames
1. Dexter Axle recommends the use of side mounting hangers when mounting axles to tubular type frames. These
hangers provide a convenient means for bolting the axles in place. All of the necessary components are included
in the Side Mount A/P kits listed in Chart 1.
2. Refer to Chart 2 to find the mounting bracket dimensions of your axles. This chart shows the dimensions from the
wheel center to the bolt holes of the brackets.
3. The preferred way to use the side mount hanger is to pre-assemble the hangers to the axle using the hardware
provided in the A/P kit. Make sure the hangers are clamped firmly against the top surface of the axle brackets
and the bolts are tightened to the torque specifications shown in Chart 1. Position the axle assembly on the frame
rails in the desired location and weld the side mount hangers to the frame.
4. Axle bracket position is the distance as measured over the outboard edges of the brackets. This dimension is
usually matched to the outside measurement of the frame members but depending on the type of frame may
not always be suitable. The preferred arrangement should place the longest vertical section of the axle bracket
directly under the most rigid section of the frame member.

13

Installation Suggestions

OUTSIDE FRAME

Side Mount Installation
Figure A

OUTSIDE BRACKET DIMENSION

Washer(s) must be placed against the
slotted hole in the axle bracket.
NOTE: Low profile brackets have plain
round holes.

Side mount hangers should be welded to frame with three (3) ¹⁄₄" fillet welds, 2¹⁄₂" long on each side of the hanger
and a fillet weld on each end. Welds should meet the quality standards of the American Welding Society, D1.1,
Structural Welding Code.

Axle
Size
#8
#9
#10
#11
#12
#13

Attaching Parts Kits and
Torque Specifications – Chart 1
A/P Kit
A/P Kit
Bolt
Top Mount
Side Mount
Size
A/P-161-00
A/P-165-00
1/2"
A/P-161-00
A/P-165-00
1/2"
A/P-148-00
A/P-166-00
5/8"
A/P-148-00
A/P-167-00
5/8"
A/P-148-00
A/P-168-00
5/8"
A/P-148-00
A/P-169-00
5/8"

Torque
Ft. Lbs.
70-90
70-90
120-155
120-155
120-155
120-155

Side mount hangers and fasteners for mounting axle are provided in the Attaching Parts Kits shown in Chart 1.
Torque fasteners to levels specified in Chart 1.
Attachment to 'C' Channel or 'I' Beam Type Frames
1. Refer to Chart 2 to find the mounting bracket dimensions of your axles. This chart shows the dimensions from the
wheel center to the bolt holes of the brackets.
2. Lay out the bolt hole locations on the bottom flanges of the frame rails. Make sure the hole pattern matches the
mounting brackets of your axles and is properly oriented to allow proper alignment of the axle(s).
3. An alternate method for determining hole location is to position the axle assembly on the frame rails, align it
perpendicular to the trailer centerline, clamp in place and transfer the holes directly from the brackets.
4. Drill the holes through the frame rails and attach the axle using the hardware provided in the A/P kit. Tighten the
bolts to the torque specified in Chart 1.

14

Installation Suggestions

CAUTION
• When bolting to structural shapes that have tapered flanges, bevel
washers must be used to prevent uneven clamping and bending of
the fasteners.

Top Mount Installation
Figure B

“C” channel frames should be
reinforced in the area over the axle(s).
Use bevel washers when
bolting to structural steel.

CAUTION
• 'C' channel and 'I' beam type frame sections should be reinforced
in the area over the axle mounting brackets. It is recommended that
the vertical leg of the axle bracket be positioned directly under the
vertical segment or reinforcement of the frame member.
Start Angle of Trailing Arm
Mounting Hole to Wheel Center - Dimension "X" (Inches) – Chart 2
45° Down
Torflex®
Axle Model

32° Down

22.5° Down

10° Down

0°

10° Up

22.5° Up

Mounting Hole
Spacing (Inches)

No
Full
No
Full
No
Full
No
Full
No
Full
No
Full
No
Full Dim "D"
Load Load Load Load Load Load Load Load Load Load Load Load Load Load
(Top)

Dim "E"
(Side)

#8 (4" arm)

5.21

6.08

5.77

6.33

6.08

6.38

6.32

6.29

6.38

6.08

6.32

5.75

6.08

5.21

7.75

8.00

#9 (6" arm)

6.62

7.92

7.47

8.30

7.92

8.38

8.29

8.24

8.38

7.92

8.29

7.44

7.92

6.62

7.75

8.00

#10 (6" arm)

6.74

8.04

7.59

8.42

8.04

8.50

8.41

8.36

8.50

8.04

8.41

7.56

8.04

6.74

8.00

8.00

#10L (6" arm)

6.74

8.04

7.59

8.42

8.04

8.50

8.41

8.36

8.50

8.04

8.41

7.56

8.04

6.74

8.00

8.00

#10F (6" arm)

6.74

8.04

7.59

8.42

8.04

8.50

8.41

8.36

8.50

8.04

8.41

7.56

8.04

6.74

8.00

8.00

#11 (6" arm)

7.74

9.04

8.59

9.42

9.04

9.50

9.41

9.36

9.50

9.04

9.41

8.56

9.04

7.74

9.00

9.50

#12 (6" arm)

7.74

9.04

8.59

9.42

9.04

9.50

9.41

9.36

9.50

9.04

9.41

8.56

9.04

7.74

9.00

9.50

#12T (6" arm)

7.87

9.17

8.72

9.55