Torque Arms and Torque Rods

What is a Torque rod?

A torque rod can also be called a radius rod, radius arm, torque arm, or dog bone. Torque rods are suspension links that are meant to limit the movement of the axles without limiting suspension articulation. Torque arm suspensions are very common on medium and heavy-duty trucks and trailers.

Torque rod components

Torque rods are simple and have only a few parts. They will have two ends connected by a shaft, and each end will contain a bushing. The shafts are typically made from steel or aluminum with a solid or hollow construction. Most torque rods will be straight, but on certain suspensions, they may be purposely curved to allow clearance to suspension components. It is important to know how the design of the suspension that you are working on before deeming a torque rod damaged by being bent. The bend may be engineered into the torque rod for clearance purposes.

Torque arm bushings

The bushings located in the ends of the torque arms are the only wear areas of the torque arm. As the vehicle moves, the bushings are absorbing the road shock to prevent damage to other suspension components. Over time the material in the bushings will wear out. When the material wears the torque arms will start to allow excess movement of the suspension components, and this may show itself as tire wear or dog tracking. In severe cases, it can cause universal joint wear or even driveline damage. Torque rod bushings should be inspected for wear and excess movement during preventative maintenance. Worn bushings or damaged torque arms should be immediately replaced when issues are found.

Torque Rod Bushing Mounting Types

Various suspension designs will require mounting types that work correctly with the elements of the suspension design. The three main bushing types used in torque rods are straddle, tapered, and sleeve. These will all attach to various torque rod mounts, and it is important to know how to identify these different types to ensure the correct replacement. This is critical whether you are replacing the entire torque arm or just the bushings! The information below will help with identifying different bushing types for replacement, but on all bushings types, you should measure the width of the bushing and the outer diameter of the bushing where it is pressed into the arm.

If the steel on the torque rod is rolled around the bushing and you are unable to measure the OD, this is a high-confinement bushing, and the entire torque arm will need to be replaced.

Torque Rod Bushing Types

Torque arm bushing replacement

We recommended that a shop perform the replacement of torque rod bushings. Replacing the bushings requires a large hydraulic press and correctly sized press dies. Patience and a lot of practice aide in replacing torque rod bushings and incorrectly installing bushings can easily destroy them. In some cases replacement may require a special torque rod bushing tool.

Measuring a torque rod for replacement

Measure:

1. Center to Center – The length of a torque rod is measured from the centers of each bushing. Torque rod length is a very important measurement to maintain the vehicle alignment.
2. Bushing Side A – Start with the width and the outer diameter and then measure the other bushing features depending on the type.
3. Bushing Side B – Not all bushings will be the same on both sides. Even if it looks the same, verify the measurements!
4. Bushing Angles – Straddle type bushings may have the bolt holes in line with the torque rod shaft, or they may be set on an angle. Bushing angle is important for mounting as most bushings will not be able to rotate after they are installed in the torque rod and attempting to rotate them may damage them.
5. Shaft Diameter – The diameter of the shaft may be important if clearance is an issue.