FAQ: Axle Assemblies
FAQ provides basic trailer parts information for the DIYer or business owner. For more information, please call Dexter toll free at (877) 973-3632.
Leaf spring (tube) and torsion
A leaf spring axle requires a separate suspension system, which is comprised of leaf springs and hangers that must be mounted to the trailer. Torsion axles have an integral rubber suspension system built into the axle beam.
Leaf spring axles have replaceable suspension components, which are generally readily available from multiple sources. In addition, these suspension components can often be quickly replaced in the field. On the other hand, many times when a torsion axle is damaged, the entire axle must be replaced, leading to an additional investment and higher cost.
Yes. However, Dexter Axle (Redneck’s axle supplier) does NOT recommend this type of mounting directly to the frame. When this is done, the load is transferred directly to the frame and usually results in a very harsh ride. In addition, total axle capacity is also reduced by at least 50%.
These terms refer to the position that the leaf springs are mounted to the axle. With “overslung” the leaf springs are mounted over the axle tube and with “underslung” the springs are mounted under the axle tube. “Underslung” mounting results in a lower deck height.
An axle spindle is the end section of an axle where the trailer hub is mounted.
By using a straight or drop spindle axle, by using suspension hangers of different heights, or by using “overslung” or “underslung” spring mounts.
As the name implies, a straight spindle, and therefore the center of wheel hub, is in-line with the center of the axle beam. With a drop spindle, the center of the wheel hub is offset from the center of the axle beam. Drop spindles are most often used for applications that require a lower trailer frame and deck height.
You must have both the correct hub face and spring center.
Hub face measurement is the distance from the wheel mounting surface on one hub to the wheel mounting surface of the opposite hub.
This is the distance from the center of one spring seat to the center of the opposite spring seat.
Track width is used in dual wheel applications and is the measurement from the middle of the two tires on one side of the axle to the middle of the two tires on the opposite side. Hub face is generally referenced in measuring or referring to single wheel trailer applications.
Axle overhang is the difference between the hub face measurement and the spring center measurement. This measurement can best be designated in two ways: each end of the axle or both ends of the axle added together.
This measurement is important and is used to calculate the actual beam strength of the axle, because as the length of the overhang increases, the more stress is placed on the axle beam.
A 60R axle is rated at 6,000 lb capacity utilizing a light-duty wall axle tube. With the light-duty tube, overhang is limited to 15” when using a straight spindle.
A D60 axle is rated at 6,000 lb capacity utilizing a medium-duty wall axle tube. With the medium-duty wall tube, overhang can be expanded to 20.” All other components of 60R and D60 axles, including spindle, hub, brake, and bearings, are the same.
The 10KHD heavy duty axle uses a larger diameter spindle; therefore, the corresponding spindle nuts and spindle washers will be larger. The bearings will also be larger on the 10KHD (395S inner, 387A outer) than on the 10KGD (387A inner, 25580 outer). On a brake axle, the 10KHD also has larger drum brakes (12 ¼” x 4”) than the 10KGD (12 ¼” x 3 3/8”)
Cambered axles have a slight upward bend in the middle of the axle beam, which is approximately 1° on Dexter axles. As load is applied, the camber in the axle flexes and the tires make full contact with the road.
If the axles you are using are not cambered, you will typically encounter increased tire wear on the inside edge of your tires.
All axles have a gross axle weight rating, or GAWR. This term refers to how much weight your axles can carry and is determined by the lowest rated component in the assembly.
There are numerous factors that determine the weight rating on a particular axle, including such items as tube diameter, tube wall thickness, tube length, overhang measurement, bearing combinations, and the type of hub that will be used.
The axle spindle is mounted to a torsion arm that is permanently attached to a solid machined bar, which is surrounded by rubber cords within the axle beam. As load is supplied, shock absorption is provided by the solid bar rotating, causing a rolling/compressive resistance in the rubber cords. This rotating action provides a similar functionality as conventional leaf springs.
The torsion arm is the manufacturing method that that enables the axle spindle to be attached to the axle beam. One end of the torsion arm is attached to the solid bar, which slides into the axle beam the other end has the spindle mounted to it. The torsion arm is often called the “dog bone” because of its shape.
Torsion axles have a 5-year manufacturer’s warranty, whereas leaf spring axles have a 2-year manufacturer’s warranty. Rubber cushioning eliminates metal-to-metal contact and there are no suspension parts to wear out.
Independent suspension on the torsion axle allows for a quieter, smoother ride with less sway. Torsion axles also have multiple starting angles to achieve various trailer heights.
This is the angle of the torsion bar relative to the horizontal plane (trailer frame). Torflex axles are available in different starting angles, which determine the trailer frame height.
No. Because the different starting angles are built using different components, the starting angle cannot be changed once the axle is built.
The common angles are 45° down, 22.5° down, 0°, 10° up, and 22.5° up.
0° starting angle: The center of the spindle is on the same horizontal plane as the center of the axle beam.
Up starting angle: The center of the spindle is above the center of the axle beam, which lowers the trailer frame.
Down starting angle: The center of the spindle is below the center of the axle beam, which raises the trailer frame.
No, hangers are not required on torsion axles. Torsion axles are mounted directly to the trailer frame using brackets that are an integrated part of the axle assembly.
No. The mounting bracket is an integral part of the axle assembly and cannot be moved. Because of this, the Outside of Bracket (OB) measurement is required when ordering a Torflex axle. Also, the beam of a Torflex axle should not be welded because the internal rubber cords can be damaged.
Hub face (HF) measurement, outside of bracket (OB) measurement, starting angle, and rubber suspension capacity.
This is the distance from the wheel mounting surface on one hub to the wheel mounting surface on the opposite hub.
This is the distance from outside of the mounting bracket on one end of the axle to the outside of the mounting bracket on the opposite end of a torsion axle.
Because torsion axles are mounted directly to the frame, this is same measurement as the outside of the trailer frame where the axle will be mounted.
This is the method to mount the Torflex axle when the trailer frame is built using “C” channels or “I” beams. The mounting bolts are assembled through the top of the bracket and bottom flange of the frame rail.
This is an optional mounting bracket that can be used to mount Torflex axles when the trailer frame is built using tubular members. The mounting bolts are assembled through the side of the torsion axle bracket and side mount brackets. The side mount brackets are then welded to the trailer frame.
Standard orientation is where the longest vertical surface (leg) of the Torflex mounting bracket is positioned toward the middle of the axle.
This is an optional mounting bracket where the longest vertical surface (leg) of the Torflex mounting bracket is positioned toward the outside of the axle.
It depends on the setup of the trailer frame. The longest vertical surface (leg) of the mounting bracket should be under the vertical segment of the frame member.
Yes, if using the “T” series of Torflex axles. The “T” series uses a special axle beam and ruggedized components to stand up to the demands of a triple axle application and is available in the #12, #13, and #14 series of Torflex axles.
Yes, if the axle was originally ordered with the replaceable spindle option, which Dexter Axle began offering in early 2014.
No. Torsion axles use the same hubs and hub/drums as comparable leaf spring axles.