How To Replace Heavy-Duty Springs On Tri-Axle Boat Trailers

Replacing heavy-duty springs on tri-axle boat trailers is a task that requires careful attention to detail and a working knowledge of trailer mechanics. While it is possible to replace these springs yourself, it is important to prioritize safety and only take on the task if you feel confident in your skills. The process involves jacking up the trailer, removing the old springs, and installing new ones, ensuring that all measurements and weight capacities are accurately matched to the trailer's specifications. It is also crucial to replace the U-bolts and consider replacing the shackles and equalizer for optimal performance and safety.

Measure the old springs for replacements

When measuring old trailer springs for replacements, it is important to accurately take the correct measurements to ensure the function of your trailer and make replacing them easier. Using replacement trailer springs with the correct length will keep the axle in the same position, eliminating the need to move fenders or suspension components like spring hangers or equalizer hangers. Matching your weight capacity, arch, and leaf count will keep the ride height of the trailer the same and keep the ride characteristics the same.

Firstly, jack up your trailer using jack stands to allow the axle to hang freely. It is also necessary to measure your trailer while it is unloaded, as the weight of the load may cause inaccurate measurements.

Next, determine the type of trailer spring:

• Slipper Spring - Open Eye
• Slipper Spring - Radius End
• Slipper Spring - Flat End
• Slipper Spring - Hook End

Then, measure the width of the spring. Most trailer springs for boat, motorcycle, horse, camping, flatbed, and utility trailers are 45mm wide. To determine the width, simply measure along the centre of the top leaf.

After that, measure the length of the trailer leaf spring. If you are replacing a spring, getting the same length is important. Measure the free length when the spring is not under load. When determining length, measure from the centre of one spring eye to the centre of the other spring eye for double-eye trailer springs. Measurements will vary depending on the age and fatigue of your spring.

Finally, determine the capacity of the springs. Determine the rating of your trailer axle and then select the capacity of your springs. If you have a 1500 kg-rated trailer axle with two springs, you will use two 750 kg-rated trailer springs or higher. Please note, the capacity ratings are for each individual trailer spring.

Choose the correct spring type

When it comes to choosing the correct spring type, there are several factors to consider. Firstly, it is important to understand the different types of springs available. The three basic types of springs are mechanical, gas, and air springs.

Mechanical springs are the most common type and are further divided into three subcategories: helical springs, leaf springs, and disc springs. Helical springs, including compression and extension springs, are the most widely used type in product manufacturing. They are open-coiled springs that provide an opposing force when compressed or stretched. The ends of these springs can be left open or closed, with the latter having squared-off ends where the last coil is flattened against the adjacent one. Leaf springs, on the other hand, are made of rectangular metal plates or "leaves" that are fastened together. They are commonly found in large vehicles such as trucks and train carts. Disc springs, also known as disc washers or spring washers, are perfect for high-load applications in tight spaces due to their conical disc shape.

Gas springs, commonly used in the automotive industry, employ the pressure of a cylinder and a rod along with nitrogen or other inert gases to produce a force. Air springs, on the other hand, have been used in heavy-duty applications for over a century, especially in suspension systems. They consist of a column of air contained within a bellows-shaped rubber-and-fabric container, providing spring motion.

Now, let's discuss how to choose the right spring type for your specific application. It is crucial to consider the function you require the spring to perform. If you need a push-back motion or energy release, a compression spring would be ideal. If you require a pulling action or extension and retraction, an extension spring (also known as a tension spring) is more suitable. For a rotating or radial movement, a torsion spring would be the best choice. Additionally, factors such as spring rate, spring constant, end type, wire diameter, and material should be considered to avoid critical failure.

For boat trailers, leaf springs are commonly used, and it is important to match the existing spring specifications when replacing them. This includes matching the spring shape and type (double eye, slipper-open eye end, slipper-hook end, etc.), length, width, weight capacity, arch, and leaf count. Taking accurate measurements and choosing the correct replacements will ensure the proper function of your trailer and make the replacement process easier.

Prepare the right tools

Preparing the right tools is essential for successfully replacing heavy-duty springs on a tri-axle boat trailer. Here are some detailed instructions to guide you through the process:

Measuring and Selecting the Correct Springs:

Firstly, it's important to accurately measure your current trailer springs to choose the right replacements. Measure the length of the spring when it's not under load by jacking up the trailer frame. Match the spring type, such as double eye, slipper-open eye end, slipper-hook end, etc. Count the number of leaves, as each layer of spring metal is considered a leaf. Ensure the weight capacity, arch, and leaf count match to maintain the trailer's ride height and characteristics.

Spring Compressor:

When dealing with coil springs, safety should be a top priority. A spring compressor is essential for removing and installing coil springs safely. It helps to compress the spring, releasing the tension, and allowing for safe disassembly and assembly of the surrounding components. Make sure to select a spring compressor suitable for your specific suspension design.

Striking Pry Bar Set:

Screwdriver-handled striking pry bars, such as the Mayhew Dominator bars, are an excellent addition to your toolkit for suspension work. They will come in handy when checking for play in suspension parts and provide leverage for various tasks.

Ball Joint Service Tool:

While not all ball joints require pressing, a ball joint press is a valuable tool. It resembles a large C-clamp with cups to receive the ball joint and can also be used for other tasks like changing idler arm bushings.

Ball Joint Separator:

A ball joint separator, also known as a pickle fork, is a forked wedge used to separate the ball joint from the spindle or knuckle. This tool is essential for safely removing ball joints without causing damage to other components.

Air Hammer:

Although not necessary, an air hammer can be a valuable asset when dealing with corrosion-affixed parts. It provides the power and force needed to tackle stubborn, rusted components. Ensure you have a suitable compressor, lines, and fittings to operate it effectively.

Other Tools:

Some other tools that may be useful during the spring replacement process include various wrenches, a gear puller, and a cutting wheel for removing rusted bolts. Additionally, having a set of new U-clamps and bolts is recommended for a secure and long-lasting installation.

Remember to wear appropriate safety gear, including gloves and eye protection, when working with springs and suspension components.

Remove the old springs

Before you start, make sure you have a pair of safety glasses to protect your eyes from dirt and rust.

Park your trailer on a flat, solid surface, like a concrete driveway, and use wheel chocks to prevent the trailer from rolling.

To remove the old springs, first, spray penetrating oil on the nuts and bolts to help loosen them and prevent damage as you remove them.

Next, look for the triangular mounting bracket beside the leaf spring. It will be bolted to a bar that attaches to the underside of your trailer. Use a ratchet wrench to remove the bolts and set them aside in a safe place.

Now, locate the U-bolts above the shock absorber bracket and remove them by twisting the nuts counterclockwise. Then, slide the bolts off the axle.

At the front and back ends of the wheel, you will see eyelet bolts securing the leaf spring to the underside of the trailer. Again, use your ratchet wrench to remove these bolts, supporting the spring as you do so to prevent it from crashing down.

Repeat this process for the second leaf spring.

When purchasing new springs, it is important to accurately measure your trailer springs and choose the correct replacements to ensure the proper function of your trailer. Matching the weight capacity, arch, and leaf count will maintain the ride height and characteristics of your trailer.

Install the new springs

To install new springs on a tri-axle boat trailer, you will need to follow these steps:

Firstly, it is important to choose the right type and size of springs for your trailer. Measure the old springs carefully and select new springs with the same dimensions, including the same length, width, and leaf count. You will also need to ensure that the spring capacity matches your trailer's weight.

Next, you will need to jack up the trailer and remove the wheels for easier access to the springs. Place the jack underneath the lower control arm to provide support and prevent it from falling.

Now, you can begin to remove the old springs. Disconnect the sway bar and remove the shock absorber, which is often located through the centre of the spring. Use a spring compressor to compress the spring before attempting to remove it. Once the spring is compressed, you can unbolt it and separate the ball joint from the lower A-arm.

With the old spring removed, take the opportunity to inspect the axle for any signs of rust or damage. If the axle is in good condition, you can proceed to install the new spring.

Compress the new spring using the spring compressor and install any necessary accessories, such as insulators, gaskets, or boots. Ensure that these accessories are positioned in the same way as they were on the old spring.

Place the new spring into position, making sure that it is seated correctly and aligned with any grooves in the base of the strut. Reattach the ball joints to the control arm before releasing the spring compressor.

Now, you can begin to reassemble the suspension components. Reinstall the shock absorber, ensuring that it fits through the centre of the spring if applicable. Reattach the sway bar to the lower A-arm, tightening all bolts to the specified torque.

Finally, you can lower the trailer, re-install the wheels, and tighten the lug nuts to the specified torque.

Once the new springs are installed, it is recommended to take the trailer for a short drive to test out the new suspension. Ensure that your handling feels normal during the test drive. If anything feels off, stop driving and have a professional inspect the components to ensure correct installation.

Frequently asked questions