Leaf Spring Parts - Semi Trucks
Semi Truck Leaf Spring Parts
Attaching the leaf spring to the frame and axle requires multiple different parts. First part connecting to the frame is the leaf spring hanger. These hangers bolt on or weld to the frame of the semi truck. Next you have a shackle which connects to that hanger which allows the leaf spring to flatten when going over uneven roads. You have the leaf mounting bolts or pins which connect the leaf spring on both ends whether that be to the shackle or to the hanger. Then you have the parts which connect the leaf spring to the axle. You have the U-bolts which are U shaped steel bolts that wrap around the leaf spring and the axle housing connecting the two. Lastly you have the U-bolt plate which connects on top or on bottom of the axle housing depending on the vehicle. This plate gives a mounting point for the bottom on the U-bolts.
What Is A Leaf Spring Hanger?
A leaf spring hanger is a bracket made out of steel which bolts on or welds to the frame of a big rig. There will always be a front of rear hanger and a rear of rear hanger. The front of rear hanger is referring to the front section of the rear of the semi truck frame. Then there is a rear of rear which is referring to the rear section of the rear of the semi truck frame, a hanger mounts at both points. The front of rear hanger bolts onto the front of the leaf spring and the rear of rear hanger bolts onto a shackle then to the rear of the leaf spring. Both hangers are fixed mounting points for the leaf spring to connect to the frame.
How To Measure A Leaf Spring Hanger
Hangers will come in multiple shapes and sizes and what measurements will be needed to match up a replacement will vary. For most hangers the bolt hole diameters, length of the hanger and the center hole to center hole measurement will be needed. Take a look at the diagram below to get a better idea of the measurements we use to identify this hanger.
What Is A Leaf Spring Shackle?
A leaf spring shackles connects the leaf spring to the frame. It does this by connecting one end to the leaf spring hanger which is bolted on or welded to the frame. Then the other end of the shackle bolts to the end of the leaf spring. As a semi truck is going over uneven roads the shackle will pivot allowing the leaf spring to lengthen. Without a shackles the leaf spring would not be able to flatten causing the ride to be very rigid and stiff.
How To Measure A Leaf Spring Shackle
Shackles come in a variety of shapes dependent on the vehicle. Below is a diagram of the measurements need to properly match a replacement. You will need to know the hole diameters, the center hole to center hole measurements and the width. Take a look at the example below.
What Is A Leaf Spring Bushing?
A leaf spring bushing is a cylindrical rubber or polyurethane component that allows the leaf spring to be securely installed. The bushing also provides some cushion giving the suspension a smoother feel. Rubber leaf spring bushings are becoming less common due to how quickly they wear with age. As rubber gets old it dries which then creates cracks and then tears. Polyurethane has become a much more popular choice due to its increased longevity over rubber. One downside is that polyurethane is a stiffer material so you do get less give with the bushing while the suspension is in motion.
How To Measure A Leaf Spring Bushing
Shown below is a measurement diagram of how to measure a leaf spring bushing. The measurements you will need to take are the inside diameter (A), the under head to end of bushing length (B), the outside diameter (C) and the overall length (D). With those four measurement you can match up any replacement leaf spring bushing for your semi truck.
What Is A Semi Truck & Trailer Leaf Spring U-Bolt?
A semi truck leaf spring U-bolt is a "U" shaped steel bolt that wraps around a leaf spring and axle housing holding the two together. At the bottom of the U-bolt is a U-bolt plate which the U-bolt goes through and attaches to with nuts and washers. The U-bolts prevent the axle or the leaf springs from moving while a big rig is driving.
How To Measure Semi Truck & Trailer U-Bolts
There are four diagrams listed below that show you how to measure the different types of semi truck U-bolts. There is a diagram for square U-bolts, round U-bolts, semi square U-bolts and semi round U-bolts. For all four types you will need the same measurement but where the measurement should be taken will slightly change. The measurements you will need to properly match up replacement U-bolts are the U-bolt diameter (A), the top of U-bolt to bottom of U-bolt leg measurement (B) and the inside diameter measurement (C).
