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How To Measure Your Trailer Axle

Axle Measurements Helpful for Determining Proper Replacement:

1. Hub Face - Outside of Hubface across Axle to Outside of opposing Hubface (Essential) ____________

2. Spring Center - Center of Leaf Spring Across Axle to Center of Other Leaf Spring(Be Very Precise)___________

3. Brake Flange - Outside of Brake Flange Across Axle to Outside of Opposing Brake Flange (If Applicable on 3,500lb Capacity Axle, not usually present on 2,000lb Axle)__________

4. Overall Length(Tip to Tip)_________


 Parts Needed To Replace Boat Trailer Axle Suspension System 

Not all trailer parts are identical and standard, but the concepts of these parts are similar. We will start from the trailers frame and work down. This will detail all the required parts to replace your boat trailers suspension. 

Leaf Spring Hangers
You will first have your trailers leaf spring hanger system mounted to the frame of your trailer. These assemblies differ from difference types of trailer frames. They essentially are U-Shaped Metal pieces that hold your leaf springs. We call them Leaf Spring Hangers. On Steel Box Tubing Frame trailers, they are welded to the frame of the trailer. On C Channel Frames, they are either welded or bolted with two bolts to the frame of the trailer. On Aluminum I Beam trailer frames, they are bolted to the frame of the trailer. Regardless of your particular application, these parts can become worn or rusted over type,requiring replacement. If your previous pieces were welded, replacements would requiring welding as well. If your previous pieces were bolted on, the replacements will be as well. These Hangers are different for each type of Leaf Spring. 

Leaf Spring Shackles (With Double Eye Springs)
These components are only present on trailers that have Double eye style leaf springs. You will notice Double eye springs by the presence of two completely closed eyes, one of each side. On Single Axle Trailers, their will be two of these located on the rear eye of the leaf spring. There will be two flat pieces of metal with two holes drilled in them. On Tandem Axle trailers, their will be four of these located at the connection point of both leaf springs. These can become worn over time or rusted and require replacement. 

Trailer Equalizer Bar (On Double Eye and Reverse Curve Springs)
This Component will be located at the connection point of your trailers leaf springs. This performs the equalization process of weight while towing. On Double Eye Leaf Springs, this component is Triangle Shaped, has three bolts mounted through it, and has Leaf Spring Shackles that are mounted to the Leaf Springs. On Reverse Curve Leaf Spring set ups you will notice a diamond shaped equalizer bar with three bolts, two mounted to either leaf spring, and one main bolt mounted to a center leaf spring hanger. 

Leaf Spring Mounting Bolts
These Bolts hold your Leaf Springs into the above Leaf Spring Hangers, and also to the center equalizer bar on your trailer. They typically are either 1/2" or 9/16" diameter bolts. They will will mount your Leaf Spring to your trailers hangers loosely to allow movement. It is very common that these will rust and require replacement over time. These Bolts ride inside the Eyes of the leaf springs and equalizer bars inside Nylon bushings that will already be present. 

Trailer Leaf Springs
The Next component that all the above components mount to. Their are three main types of Trailer Leaf Springs: Double Eye, Slipper, and Reverse Curve Springs. Each Spring has some unique components that allow it to actually suspend correctly. It is important to keep these parts consistent when replacing, as its part is integral to allow the proper function of your leaf spring. The easiest identifier of these leaf springs is is the way they mount to the trailer. Double Eye springs have two closed eyes, one of each end. Slipper Springs have one closed end, and one flat end. Reverse Curve Springs have one Closed Eye, and one Curved, but not quite closed eye. 

Leaf Spring to Axle Mounting U-Bolts
These U-bolts are located at the connection point of your Trailers Leaf Spring and Axle. You will notice both U-Bolts and axle plates holding your axle and leaf springs tightly together. The Size and Dimension of these U-Bolts is determined by the dimension of your trailers axle. They will either be square or round, depending upon the shape of your axle. It is not uncommon to have to cut these off your current axle in order to replace them.