How To Replace Heavy-Duty Springs On Boat Trailers

Boat trailer springs are an essential part of trailer suspension, and they require regular inspection and maintenance to ensure safe and smooth operations. While trailer springs are designed to withstand heavy loads and prolonged use, they can eventually wear out, break, or become corroded, necessitating replacement. Replacing trailer springs can be a challenging task, often requiring specialised tools and mechanical expertise. It is crucial to select the correct replacement springs that match the weight capacity, arch, and leaf count of the original springs to maintain the trailer's ride height and characteristics. This process involves precise measurements and attention to detail to ensure a proper fit. When replacing trailer springs, it is recommended to unload the boat from the trailer, work in a spacious area, and have access to a range of tools, including jack stands, hammers, chisels, and penetrating oil.

How to measure trailer leaf springs

To measure trailer leaf springs, you must first determine the type of trailer spring you are working with. The types of trailer springs include:

• Slipper Spring - Open Eye
• Slipper Spring - Radius End
• Slipper Spring - Flat End
• Slipper Spring - Hook End
• Double Eye Springs
• C-Hook (reverse curl) Springs

Once you have determined the type of spring, you can then begin to take the necessary measurements. It is important to note that you should always inspect your trailer springs for cracks, breakage, and rust before taking any measurements.

First, measure the width of the spring. Most trailer springs for boats are 45mm wide. To determine the width, simply measure along the center of the top leaf.

Next, measure the length of the trailer leaf spring. This measurement should be taken when the spring is not under load, and the trailer is unloaded. For double-eye leaf springs, measure from the center of the front bushing in a straight line to the center of the rear bushing. For hook-end, flat-end, and radius-end leaf springs, measure from the center of the front bushing in a straight line to the end of the spring.

After you have measured the length, determine the capacity of the springs. This can be done by first determining the rating of your trailer axle and then selecting the appropriate capacity for your springs. For example, if you have a 1500 kg-rated trailer axle with two springs, you will need two 750 kg-rated trailer springs or higher.

Finally, measure the free open and arc of the trailer spring. These measurements are for reference and will change over time as the spring fatigues. By taking these measurements, you can understand the importance of replacing all of your springs simultaneously rather than one at a time.

Remember, it is highly recommended to change trailer springs in pairs to avoid causing your trailer to lean to one side due to spring fatigue.

The best method for replacing leaf springs

Replacing leaf springs on a boat trailer is a challenging but rewarding DIY job. The process can be done in half a day and will save you money on repairs. Here is a step-by-step guide to the best method for replacing leaf springs:

Step 1: Prepare and Inspect

Before starting, gather the necessary tools and safety equipment. Wear protective gear, including gloves and eye protection, to safeguard against rust and metal shards. It is also recommended to use toilet ring wax on your trailer springs to prevent rusting. If your springs are already heavily rusted, an angle grinder with a cut-off disc can be used to remove the old U-bolts. Additionally, spray penetrating lubricant on nuts and bolts to help with their removal.

Step 2: Measure and Source the Right Springs

Accurately measuring your current trailer springs is crucial for selecting the correct replacements. Match the shape and type (double eye, slipper-open eye end, slipper-hook end, slipper-flat end, or slipper-radius end), length, width, and leaf count. You can then source the new springs from a trailer shop or online.

Step 3: Jack Up and Block the Trailer

Use a small bottle jack to raise and support the trailer frame, taking pressure off the suspension. Block the trailer wheels to prevent movement and ensure stability during the replacement process.

Step 4: Remove Old Springs

Cut off the U-bolts using an angle grinder or a sawzall blade. Remove the bolts connecting the leaf spring eyes to the trailer frame. You may need to use a heavy-duty socket wrench or an impact driver to loosen stubborn nuts and bolts. If they are severely rusted, consider using a torch to heat them, but be cautious to avoid damaging nearby components.

Step 5: Install New Springs

With the old springs removed, fit the new leaf springs loosely in place. Slide the new springs underneath the axle, ensuring the bolt flange on the trailer lines up with one end of the spring. If your spring has a flat slipper end, seat that end first, then line up the bolt hole.

Step 6: Secure with New Fasteners

Loosely position new U-bolts around the axle and springs. Adjust the bottle jack as needed to align the remaining eye bolt with its corresponding flange. Alternately tighten all fasteners until everything is seated securely. Finally, lower the jack and give all fasteners a final tightening.

Post-Installation Care

After installation, consider applying a coat of paint or rust inhibitor to your new leaf springs to prolong their life and prevent corrosion. This is especially important if you store your trailer outdoors or in a humid environment.

When to replace trailer springs

Trailer springs are an essential part of any trailer's suspension system. They absorb shock, stabilise the load, and help maintain balance while driving. However, like all vehicle parts, they wear out over time, causing bumpy rides and discomfort. Here are some detailed signs that indicate when it's time to replace your trailer springs:

Visible Cracks

One of the most common signs of spring failure is the appearance of cracks in the metal, especially around the grooves where the leaves connect. Cracks can lead to further damage and even complete spring breakage, so it's best to address them promptly.

Sagging or Slouching Trailer

If you notice that your trailer sags or leans towards the front or back when loaded, it's a sign that your springs are worn beyond repair. Sagging is usually easy to spot and indicates that the springs are unable to support the weight of the load effectively.

Loss of Arches

While it's normal for trailer springs to flatten slightly under load, they should not lose their arches completely. If this happens, it could be a sign that the springs need replacement or that the trailer is overloaded. A healthy leaf spring will still be curved when loaded and should only flatten out a little, losing no more than 1.5 inches of the arch.

Swaying Trailer

Trailer springs play a crucial role in stabilising your trailer and preventing it from swaying. If you notice excessive swaying while driving, especially if it's a new development, it could indicate that your springs are wearing out. However, before jumping to conclusions, check the tongue weight and weight distribution as these factors can also contribute to swaying.

Excessive Rust and Corrosion

Leaf springs are prone to corrosion over time, but excessive rust can compromise their strength and load capacity. Keep an eye out for chunks of rust flaking off the springs or large amounts of rust beyond surface-level. Corrosion paired with other issues like cracks or sagging is a definite sign that it's time for new springs.

Bumpy Ride and Unbalanced Trailer

If you're experiencing a bumpy ride or if your trailer seems out of balance, it could be a sign that the leaf springs are unable to absorb shocks and stabilise the load effectively, indicating the need for replacement.

Regular Maintenance and Inspection

To extend the lifespan of your trailer springs, regular maintenance and inspection are key. Inspect your springs at least once every 12,000 miles or when you notice any of the above signs. Look for cracks, sagging, corrosion, and uneven riding. Proper maintenance can help identify issues early on and prevent unexpected breakdowns.

Remember, replacing trailer springs can be done by following the correct measurements and choosing suitable replacements. Always replace springs in pairs to ensure even wear and maintain a balanced load.

Different types of trailer springs

Trailer springs are an essential part of trailer suspension. There are several types of trailer springs, each with its own unique design and functionality. Here is an overview of the different types of trailer springs:

Leaf Spring Suspension:

Leaf spring suspension is a widely used and cost-effective type of trailer suspension. It consists of a series of curved springs or "leaves" that are stacked and attached to the underside of the trailer's axle using hangers and U-bolts. Leaf springs act as shock absorbers, flexing and releasing when encountering bumps, which provides a smoother ride. Tandem and triple-axle trailers often feature an equalizer that links the springs and helps transfer energy between axles when going over uneven surfaces. Leaf springs are long-lasting, easy to repair or replace, and can carry substantial loads. They are available in various configurations, from light-duty single-leaf to heavy-duty multi-leaf setups.

Double Eye Leaf Springs:

Double Eye Leaf Springs are a common type of leaf spring setup. They have three distributed loading points that minimize stress on the chassis and, to some extent, on the axle. These springs are ideal for single-axle trailers, but they may not offer the same level of side-to-side stability as other options for multi-axle setups. Double Eye Leaf Springs also take up more space under the chassis, which can limit how low the deck height can be.

Slipper Leaf Springs:

Slipper Leaf Springs have the fewest moving parts among all types of springs. They provide good lateral stability and are particularly advantageous for trailers with two or more axles due to the extra constraint they offer. On single-axle trailers, Slipper Leaf Springs help achieve a lower deck height as the distance between the chassis and the spring is quite compact. However, they can be noisy over bumpy roads, and an anti-rattle version is available to address this issue.

Parabolic Spring:

The Parabolic spring is the modern version of the leaf spring, usually consisting of a single leaf with a thicker centre that tapers out to the ends in a parabolic curve. Parabolic springs offer a smoother ride, weigh less than standard leaf springs, and do not suffer from interleaf friction. However, they tend to take up more space under the trailer, limiting how low the deck height can be. Multi-parabolic springs are also available, with spacers between each leaf to prevent contact.

Torsion Suspension:

Torsion suspension offers a very smooth ride due to its independent wheel suspension design. It features a rubber torsion arm system that is self-contained within the axle tube and directly attaches to the trailer frame. The rubber torsion arm twists as the trailer goes over bumps, with the movement dampened by surrounding rubber cords, providing superior shock absorption. Torsion suspension has a quieter ride, requires less maintenance, and allows for a lower trailer deck height. However, it typically has a lower load capacity compared to leaf spring suspension.

Where to buy heavy-duty trailer springs

Heavy-duty trailer springs can be purchased from a variety of online retailers, such as Amazon, The Trailer Parts Outlet, and Trailer Parts Superstore. These springs are essential for trailer suspension and come in a range of load capacities, from 2,000 lbs to 16,000 lbs.

When purchasing heavy-duty trailer springs, it is important to accurately measure your trailer springs and choose the correct replacements. This includes matching the shape and type of the spring (double eye, slipper-open eye end, slipper-hook end, slipper-flat end, or slipper-radius end), as well as the length and width. The weight capacity, arch, and leaf count should also be considered to ensure the ride height and characteristics of the trailer remain the same.

For example, Amazon offers a range of heavy-duty trailer springs, including the "2 Pair Heavy Duty Trailer Ramp Springs" with 2000 lbs torque, the "Trailer Ramp Coil Springs - Heavy Duty Trailer Springs" with 2000 lbs capacity, and the "SOUTHWEST WHEEL 3,500 lbs. Trailer Axle Suspension Kit" which includes leaf springs.

The Trailer Parts Outlet offers a range of trailer axle springs with different load capacities, including 2,000 lbs, 3,500 lbs, 6,000 lbs, 7,000 lbs, 8,000 lbs, 9,000 lbs, 10,000 lbs, 12,000 lbs, and 15,000-16,000 lbs options.

Trailer Parts Superstore also offers a wide selection of leaf springs and spring hardware for trailers. They emphasize the importance of accurately measuring trailer springs and choosing the correct replacements, providing detailed instructions on how to measure trailer leaf springs on their website.

In addition to purchasing heavy-duty trailer springs, it is recommended to also buy spring bolts, spring hangers, shackle links, and U-bolt tie plate kits to ensure a safe and smooth trailer experience.

Frequently asked questions