Trailer Running Gear Glossary
Arm Lengths
The length of the Torflex torsion arm as measured from the axis of the axle tube to the axis of the spindle.
Axle Capacity
The beam capacity of the axle model selected. This value may be derated based on the hub face and spring center or outside bracket dimensions, if the recommended dimensions are exceeded. (See G.A.W.R. for other rating information.)
Axle Combination
The number of axles to be used in your application (single, tandem, triple).
Axle Suspension
A system which provides a method for absorbing shock as well as attachment of axles to a vehicle frame.
Backing Plate
The circular, plate-shaped brake component, bolted to the brake flange or directly welded to the axle, to which all other brake components are attached.
Bracket Dimension
The dimension from the outside of one mounting bracket to the outside of the other mounting bracket.
Brake Actuation
The method by which a brake is energized. Air, Electric, Electric / Hydraulic, and Hydraulic Surge are available on most axle models.
Brake Flange
A mounting plate, attached to either the axle or the spindle, to which the brake assembly is bolted.
Brake Magnet
An electromagnet within the brake assembly that when actuated initiates the braking action.
Breakaway System
A system that engages brakes in the event of a separation of the trailer from the tow vehicle.
Camber
The angular relationship of the wheel to the road surface in the vertical plane. Axles are typically built with a pre-determined bend in the tube that compensates for the expected deflection under load.
Derate
When an axle is built to exceed the recommended overhang dimensions, the rated capacity will be diminished. (See G.A.W.R. for other rating information.)
Double Eye
Leaf springs with eyes formed in each end of the spring.
Drop Height
The distance from the center of the spindle (center of the tire) to the center of the axle tube.
Drop Spindle
A forged spindle with a cross-section that allows the axle tube to be offset from the axis of the wheel. Used for applications which require lower frame and deck heights. Some models offer a choice of drop heights.
Electric Brake
A mechanical braking system used in conjunction with drum brakes that actuates the stopping mechanism with electromagnets and levers. The electrical source is supplied from the tow vehicle by an electronic brake controller.
Equalizer
A suspension component that allows transfer of a portion of the load on one axle to the adjacent axle(s) when traversing an uneven surface.
E-Z Lube Feature
A bearing lubrication system that consists of a grease fitting installed into the end of each spindle. A channel is provided to distribute grease to the inner bearing. A special double lip seal diverts the lubricant back toward the outboard bearing, thus lubricating both bearings without hub removal.
Gross Axle Weight Rating (GAWR)
The rated capacity of the vehicle running gear as defined by the lowest rated component in the system. Those components considered are the axle beam, the suspension system, the wheels or rims and the tires.
Hanger Height
The distance (in inches) from the underside of the frame rail (top of hanger) down to the center of the hanger bolt hole.
Hub & Drum
A plain hub that has a drum attached, either integrally cast or bolted together, for use with a brake assembly.
Hub Face
The dimension from the wheel mounting surface on one hub to the wheel mounting surface of the other hub on the same axle.
Idler Hub (or Plain Hub)
The axle component that contains the bearings to which the wheel is attached. Hubs or plain hubs are used on axles without brakes.
Leaf Spring
A spring composed of several flat steel strips, bundled together to form a shock absorbing, load carry suspension component.
Lever Arm
A brake component that has the magnet at one end, a pivot point, and a linkage on the opposite end.
Load Line
The vertical center line of the tire in the finished axle.
Nev-R-Lube
A bearing system that consists of pre-adjusted and permanently lubricated bearings in a cartridge. This system eliminates all bearing adjustment and servicing. This system cannot be utilized for axles that are subject to immersion in water.
Overhang
The distance from the hub face or load line to the spring center (for Leaf Spring axles) or bracket edge (for Torflex axles.) That distance is used to calculate the beam strength of the axle.
Overslung
Leaf springs mounted on top of the axle.
Parking Brake Feature
A manually operated braking system that allows a mechanical lever to be actuated by means of a cable to set the brake. This system is similar to the emergency or parking brake on an automobile. In trailer applications, the manual actuating lever is generally near the trailer hitch. By activating the trailer brakes, the parking brake feature can be set to assist in holding the trailer in place.
Profile - Hub
Style of hub used allowing use of various wheel types.
Reverse Orientation
The longest vertical surface of the Torflex mounting bracket is closest to the hub or outboard end of the axle.
Rim Diameter
The dimension of the tire bead seat areas on a wheel or rim.
Rubber Capacity
The capacity of a Torflex axle as a result of the amount of rubber used in the assembly. Limits are determined by the axle model selected.
Shackle Link
A suspension component that connects the spring to the trailer frame. The double pivot action of the shackle links accommodates spring articulation and allows the spring to move freely.
Side Mount
A method of mounting Torflex axles when the trailer frame is built from tubular members. The mounting bolts are assembled through the side of the bracket and side mounting hangers or other suitable mounting plates.
Slipper Springs
Leaf springs that feature an eye formed at the front end and a curved surface on the rear end. The rear end of the spring bears upward against a wear resistant surface in the equalizer and/or rear hanger.
Spindle
The end section of an axle to which the hubs are attached.
Spring Center
The dimension from the center of the leaf spring to the center of the other leaf spring on an axle.
Spring Hanger
A suspension component attached to the trailer frame to which is bolted either a spring eye, shackle link, or equalizer.
Standard Orientation
The longest vertical surface of the Torflex mounting bracket is facing toward the middle of the axle.
Start Angle
The angle of the torsion arm relative to the horizontal plane, stated in the unloaded condition. This angle is a factor in determining the frame height.
Tie Plate
A steel plate utilized in conjunction with u-bolts to clamp a leaf spring to an axle.
Top Mount
Used with Torflex axles when the trailer frame is built from "C" channels or "I" beams. The mounting bolts are assembled through the TOP of the bracket and bottom flange of the frame rail.
Torflex
A torsion axle is an independent, self-contained suspension system consisting of a hollow axle tube and rubber cords surrounding an inner bar.
Track Width
The distance from the center line of one tire to the center line of the tire on the opposite side of the vehicle in single wheel applications. In the case of dual wheel, the track line is the center of each pair of wheels/tires.
U-bolt
A u-shaped double ended bolt used to attach leaf springs to an axle.
Underslung
Springs that are mounted to the bottom side of the axle.
Wheel Capacity
The load carrying ability of a wheel assembly at a specified inflation pressure.
Wheel Inset
The center line of the tire will be inboard from the hub face.
Wheel Nut (or Bolt)
A fastener used to attach wheels and/or rims to a trailer hub. Wheel nuts and bolts must be properly torqued to maintain the integrity of the entire wheel and hub system. Torque wheel bolts to the proper setting and be sure to re-check the torque setting at the intervals outlined in your service manual.
Wheel Offset
References the center line position of the wheel to the hub face. See Wheel Inset, Wheel Outset, or Wheel Zeroset.
Wheel Outset
The center line of the tire will be outboard from the hub face.
Wheel Zeroset
The center line of the tire will be the same as the hub face.