What Are Track Springs with Track Spring Diagram

What Are Track Springs with Track Spring Diagram

View All Parts From This Machine: John Deere 724J Wheel Loader
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The undercarriage of a tracked excavator, crawler dozer, or other tracked construction equipment provides the machine with its unique traveling abilities and advantages in specific terrains. But the introduction of tracks also introduces new components to the undercarriage to allow for adjustments and to extend the life of the machine and its parts.

One important part in the tracked machine world is the track spring (or recoil spring) assembly. To get a better understanding of the purpose of the track spring assembly and it’s critical role on a tracked machine, we’ve put together this short track spring overview.

A track spring assembly is connected to an idler wheel and, though track springs can vary by machine, many consists of a yoke, cylinder, and recoil spring.
» Click video to play/pause animation.

What Does a Track Spring or Track Tensioner Assembly Do?

  • The track spring assembly allows for the tension of a track to be controlled and for impacts to the undercarriage to be absorbed by the recoil spring without the force of the impact affecting sensitive parts on the machine like final drives and sprockets. 
  • As an impact absorption device the recoil spring contracts upon impact while also continually providing measured tension in the track through the control of a cylinder. The tension of the tracks on a machine will change as they become loaded with dirt or interact with different conditions in the ground and this recoil spring attempts to ensure the tracks operate within specific degrees of tension.
  • Adjustments to track tension are sometimes needed as parts on a tracked undercarriage experience wear. Continual and frequent adjustments to track tension are required for a wide-range of changes in the environment in which the machine is working, the material with which it is interacting, and even the temperatures in which the machine is operating.
As grease is added to the track spring cylinder, the cylinder piston extends from the cylinder and pushes the idler wheel forward. This extends the distance between the idler wheel and the final drive sprocket and, in turn, tightens the track. Removing grease? Everything goes the other way.
» Click video to play/pause animation.

How Do You Change the Tension of a Track with a Track Spring Assembly?

  • To change the tension of a track, grease is added to or taken from the track spring cylinder. Adding grease will increase the tension of the track and removing grease will reduce the tension in the track. While adding grease to the cylinder is most often done through a simple grease fitting, reducing the grease in the system can be unique to the machine.
  • Before increasing or decreasing the tension of a track, you should consult your operator’s manual for the exact process, proper tension requirements, and how to measure the tension of your track.
  • An overly loose track can be more prone to come loose from the undercarriage, while a too tight track reduces the efficiency of the machine and can lead to damage to other parts of the undercarriage.
Track spring locations on an excavator.
An excavator has two track spring assemblies at the front of each track with a final drive on the opposite end.

What Are the Parts of A Track Spring Assembly?

Front Idler

While not an actual part of the track spring assembly, the front idler is the undercarriage part that a track spring assembly connects to and works with to set the track tension. The front idler on a tracked undercarriage is a large wheel that guides the track along its path and sits between the track spring assembly and the track. Because of its location on the machine and the nature of its work, the front idler is built from heavy and hardened steel.


At one end of the track spring assembly is a bracket that holds the front idler in position and connects to the cylinder of the track spring. Commonly, a u-shaped design cradles the idler wheel at one end while the opposite side features a flat, cylindrical end that contacts and contains the expansion of the recoil spring.

Recoil Spring

The recoil spring in a track spring assembly is a heavy-duty spring held under pressure at all times. The use of a spring allows the track spring assembly to absorb shocks and provides a measured amount of tolerance. The spring’s ability to absorb impacts through limited movement decreases wear on the tracks and prevents damage to sensitive parts like the undercarriage when the tracks interact with resistance or become tight due to operating conditions. Because a recoil spring is mounted to the assembly under high pressure only experienced professionals should attempt to adjust or repair the recoil spring as sudden releases to pressure can result in injury and even death.

Track Adjuster or Track Tensioner

To set tension and allow for routine adjustments to track tension a track adjuster is built into the center of a track spring assembly. Often, the track adjuster consists of a track cylinder that allows for grease to be added and removed through grease valves, seals to contain grease, a cavity to hold grease, and a rod with the ability to extend and retract from the cylinder’s housing.

Track Cylinder Piston or Cylinder Rod

The track cylinder piston sits inside of the cylinder housing with one end contacting the grease cavity of the housing and the other end extending outward from the housing. As grease is pumped into the cylinder the piston extends further outside of the housing, and in turn, the distance between the far end of the track spring assembly and the other end of the assembly (connected to the idler wheel) increases. Increasing the distance of these two points adds tension to the track. Reducing the amount of grease in the cylinder shortens the distance and loosens the track.

Grease Valve

A simple grease valve allows for adding grease to the track spring assembly while often a threaded bolt allows grease to exit the cylinder.


Seals inside of the track spring cylinder on the piston contain grease in the cavity while allowing for grease to lubricate the piston and also prevent corrosive elements and debris from entering the cylinder.

Explore more parts on an excavator with our Interactive Excavator Parts Diagram.


If you’ve made it here, it should be clear how important the track spring assembly on a tracked machine is. As a part that sits right in the middle of the action, protects other sensitive parts, and allows the tracks to be properly tensioned at all times, the critical role a track spring assembly plays really can’t be underestimated.

If you’re searching for a new or used replacement track spring assembly, we’re happy to be a resource for you. Our inventory of replacement track springs is hard to match and our expert Parts Specialists are always here to help -- from advice on new vs used, assistance making sure you find the right track spring for your machine, and fast searches to find and deliver your track springs, ASAP. Just give us a call: 800-333-0650.

Track Spring Image Gallery

A diagram of the parts in a track tensioner.
While track spring assemblies vary in design, many share a common set of parts to support their common purposes.
An x-ray view of a track spring assembly.
With a little X-Ray vision you can peer inside of the track spring and better understand how the grease in the cylinder extends the piston and pushes the idler wheel forward.
Recoil springs in warehouse.
Since track springs are common across a wide range of sizes, H&R brand track springs can be as small as a few feet to roughly the size of an NFL linebacker.
Track springs on a pallet on a forklift.
Here, a large and heavy track spring takes a trip on a forklift to be loaded and sent to a waiting excavator.
A rebuilt track spring in the H&R shop.
In the H&R Recon and Rebuild shops technicians rebuild track springs, carefully disassembling the track spring, replacing worn parts, and reassembling it. This unique track spring assembly is from a Komatsu D65PX crawler dozer.
A labeled parts diagram for a track spring.
Understanding the parts of the track spring help make it clear how it functions and its importance on tracked construction equipment.