Utility, Boat, & Travel Trailer Leaf Spring Parts

Trailer Leaf Spring Parts

Below is a diagram of a trailer suspension system. In this diagram we can show all the connecting parts for a trailer leaf spring that mount it to the trailer frame and axle. In a trailer suspension system you will find trailer spring bolts, trailer hangers, U-bolt plates, trailer leaf springs, shackle straps, trailer equalizers and U-bolts.

Double eye trailer spring suspension.

What Is A Trailer Suspension Bolt?

Trailer suspension bolts attach all the various parts together that make up the trailer suspension system. These bolts will be at fixed points and pivot points on the trailer suspension. You will find suspension bolts at the shackles on both ends, the equalizer on 2 or 3 ends depending on the style and the trailer spring end that attaches to the hanger. There are two types of trailer suspension bolts. There are regular bolts which are solid and non greaseable and wet bolts which are greaseable. Wet bolts have a hole in the center of the bolt with a zerk fitting on the end to be able to add grease where as regular bolts do not.

How To Measure A Trailer Suspension Bolt

Below is a diagram of how to measure a trailer suspension bolt. You will need to know the diameter of the bolt, the under head to end length, thread length and whether it is greaseable or non greaseable. Below is an example of where those measurements need to be taken.

Trailer suspension bolt measurement diagram.

What Are Trailer Spring Hangers?

Trailer spring hangers attach the trailer leaf springs and equalizers to the trailer frame. The hangers are welded to the frame and the springs and equalizers bolt to the hangers. There are 3 different types of trailer hangers the front, center and rear. The front hanger attaches the most forward trailer spring, the center hanger attaches the equalizer and the rear hanger attaches the rearward trailer spring. Trailer spring hangers vary is shapes and lengths depending on the length and type of trailer spring installed.

How To Measure A Trailer Spring Hanger

To measure a trailer hanger you will need to know the top of hanger to center hole measurement (A), the overall height (B) the inside diameter (C) the thickness (D) and the length (E). Below is a diagram that shows where these measurements need to be taken to find a trailer hanger replacement.

Trailer spring hanger measurement diagram.

What Is A U-Bolt Plate?

A trailer U-bolt plate is a steel plate that the U-bolts go through to attach it around the trailer axle. Trailer U-bolt plates are flat and have four or five holes drilled into them. Four outside holes are for the U-bolt legs to fit through and should be a slightly larger diameter then the U-bolt leg. If there is a fifth hole in the center that is for fitting over the center bolt.

When Should U-Bolt Plates Be Replaced?

U-bolt plates most of the time can be reused. The only times that you will need to replace a U-bolt plate are under these specific circumstances. If the plate has severe rusting to the point when the metal is beginning to flake or cause pitting. If there is just surface rust on the U-bolt plate most the time that can be cleaned off, coated and reused. If the U-bolt plate is bent or broken replacement is highly suggested. Lastly if the holes in the U-bolt plate become oblong. A U-bolt leg can wear into the mounting holes in the plate causing them to become a oval shape. If this happens the U-bolt can move excessively and can be prematurely damaged.

U-bolt plate for a trailer.

What Are Shackle Straps?

Shackle traps are 3 inch to 4 and a half inch, rounded pieces of steel with holes drilled in each end that connect different parts of a trailer suspension system together. They are used in single, tandem and triple axle setups. Trailer shackle straps can be found on a single axle setup at the rear hanger connecting it to the spring. In tandem and triple axle setups they are located at the trailer equalizers connecting them to the end of the trailer springs.

How To Measure A Shackle Strap

A shackle strap is measured in three different places. The first measurement is the overall length (A), the second is the center hole to center hole measurement (B) and the third is the hole diameter (C). Those measurements will be everything you need to replace a shackle strap.

Shackle strap for trailer suspension.

What Is A Trailer Equalizer?

Trailer equalizers are a connecting point for leaf springs on trailers with tandem and triple axle suspension systems. When driving over uneven roads equalizers transfer and equalize the weight being carried between all the axles. This gives the trailer a much smoother ride, absorbing more of the impact evenly. There are 3 types of equalizers straight, curved and triangle each going to specific types of suspension systems. Below are some pictures of the different types of equalizers.

Straight trailer suspension equalizer.Curved trailer suspension equalizer.Triangle trailer suspension equalizer.

How To Measure A Trailer Equalizer

To measure a trailer equalizer there are four measurement that will need to be taken. These measurement will be the same for all types of equalizers. You will need to measure the end to end hole length (A), the end to center hole length (B), the end hole diameter (C) and the center hole diameter (D). With those four measurement you can replace a trailer equalizer quickly and easily.

Straight trailer equalizer measurement diagram.