If your tandem axle trailer is bottoming out, you may need to replace the leaf springs and equaliser bars. Leaf springs are made of high-fatigue steel that will absorb the force of impact under heavy load. Equaliser bars distribute the weight between tandem axles on either side of the trailer. A disproportionate amount of weight may be transferred to a single axle without equaliser bars installed to stabilise the suspension system. Upgrade your leaf springs and equaliser bars on your trailer to protect your axles from undue wear and tear.
Support the front of the trailer on the trailer tongue jack stand. Jack up the side on which you will be working, and support this side with a jack stand. Place jack stands under both axles near the leaf spring assembly to relieve weight from the springs.
Remove the U-bolts and retainer brackets that hold the centres of the leaf springs to the axles with a socket wrench.
Remove -- with a socket wrench -- the spring bolts that hold the forward and secondary leaf springs to the front and rear shackle hangers.
Remove the bolts that connect the leaf springs to the centre shackle straps using a socket wrench. Detach the leafs springs from the trailer by hand.
Remove the bolt that holds the centre of the equaliser bar to the middle hanger, using a socket wrench. Remove the equaliser bar with shackle straps from the trailer. Remove the shackle straps from the equaliser with a socket wrench.
Install the new leaf springs and equaliser bar in the reverse order that you removed the old ones. Reattach the shackle straps to either side of the new equaliser bar with bolts, using a socket wrench. Attach the centre hole of the equaliser bar to the middle hanger with a bolt.
Attach the leaf springs to the shackle straps at the middle of the trailer with bolts. Rotate each leaf spring up and under its axle, and attach the opposite end to the respective front or rear shackle hanger with a spring bolt, using a socket wrench.
Seat the axles in the centres of the leaf springs. Reattach the U-bolts and retainer brackets, using a socket wrench, securing the springs to the axles.
Tighten all the bolts to the manufacturer's torque specifications, using a torque wrench. Remove the jack stands and blocks, and lower the trailer.
Perform the same procedure to install new leaf springs and equaliser bar to the other side of the trailer.
Apply penetrating oil to a stuck bolt. Tap the bolt with a hammer to spread the oil farther down the threads.