How to Replace Boat Trailer Leaf Springs

Inspecting trailer leaf springs is as simple as bending down and looking, something quick you can do after unloading your boat into the water. When inspecting your trailer’s leaf springs, look for surface rust, which is to be expected and can be treated with a wire brush and rust remover. However, if the rusting is severe enough, the springs need to be replaced.

Leaf springs can also crack, especially around the center bolt and the rebound clip, which is the metal band around the leaves in front of the axle. If the rebound clip is broken or missing, the leaf spring doesn’t need replacing, but a new rebound clip must be installed. A crack or a break or separation at the ends of any of the leaves means the springs must be replaced. 

Choosing Trailer Leaf Springs

Boat trailer springs lose some of their bow shape and become elongated over time. So if one leaf spring needs replacing, all the springs on that axle should be replaced. 

If only one is replaced, the wheels will be misaligned and the trailer will not track properly when in motion. New leaf springs must correspond to the trailer’s maximum axle capacity stamped on the manufacturer’s plate. A spring rated below the maximum capacity will break when fully loaded, while a spring rated above the maximum capacity will not provide sufficient suspension movement.

Replacing Trailer Leaf Springs

Step 1. Jack up the trailer and support it on axle stands, then remove the wheel.

Step 2. Loosen the spring eye bolts at either end of the leaf spring and the U-bolts at the center of the spring. Depending on the design of the trailer, the U-bolts may either be above or below the leaf spring.

Step 3. Place an axle stand below the axle to support it, then remove the U-bolts, the spring eye bolts and the leaf spring. 

Step 4. Inspect the spring shackles for wear and replace them if necessary. Remove any rust with a wire brush and rust remover, and spray rust inhibitor on the spring shackles and hangers.

Step 5. Install the new leaf spring by tightening the spring eye bolts, then reattaching the U-bolts and tightening them a few turns at a time in a diagonal pattern in order to fasten down the U-bolt plate with uniform pressure. 

Step 6. Reattach the wheel, return the trailer to the ground and repeat the process on the other end of the axle.

Replacing Rebound Clips

Most trailer leaf springs have one rebound clip forward of the axle. Larger capacity springs may have two rebound clips, one on either side of the axle.

Rebound clips prevent the top leaf spring from breaking. When the wheel is pushed up over a bump in the road, it compresses the spring. As this happens the weight of the trailer is supported by all of the leaves working together. Then when the wheel falls back down after the bump in the road, the spring rebounds. As it rebounds, the leaves will want to spring apart, leaving all of the trailer’s weight supported by the top leaf alone. 

To replace a broken or missing rebound clip, hold the leaves together with a C-clamp, then install and tighten the new rebound clip around the leaves and then remove the C-clamp. 

New leaf springs often need time to fully bed in. After the first couple of uses, check all of the U-Bolts, the rebound clip bolts and the spring eye bolts and retighten them to remove any play. To keep the springs from wearing out faster, all it takes is a little trailer leaf spring maintenance.