Evaluating Excavator Undercarriage Wear for Low-Hour Farm Use

[MikePhua]

The Role of Undercarriage in Excavator Longevity
The undercarriage of an excavator is its foundation—supporting the entire machine, absorbing terrain stress, and enabling mobility. It includes track chains, rollers, idlers, sprockets, and tensioners. While often overlooked, undercarriage condition directly affects performance, fuel efficiency, and safety. For machines used in agriculture or light-duty work, understanding wear patterns and thresholds is essential to avoid unnecessary replacement costs.
Terminology annotation:

• Track chain: A series of interconnected links that form the continuous loop around the undercarriage.
  
• Pins and bushings: Internal components of the track chain that allow articulation and absorb rotational stress.
  
• Front idler: A wheel that guides the track and maintains tension at the front of the undercarriage.
  

How Undercarriage Wear Is Measured
Undercarriage wear is typically expressed as a percentage, with 0% being brand new and 100% indicating full wear. This percentage is calculated based on:

• Link height reduction
  
• Sprocket tooth wear
  
• Roller diameter loss
  
• Pin and bushing internal clearance
  
• Idler extension position
  

One reliable method involves inspecting the position of the front idler blocks. When these blocks are flush with the front of the track frame, the chain is considered fully worn. Another indicator is the spacing between link ends as they pass over the idler or sprocket. On new chains, the links sit tightly together. On worn chains, gaps appear—sometimes large enough to insert a fingertip and touch the bushing.
Acceptable Wear for Low-Hour Applications
For farm use or seasonal tasks totaling around 100 hours per year, a heavily worn undercarriage may still be serviceable. If the tracks maintain tension and the machine doesn’t derail, it can continue operating effectively. In fact, some operators have run machines with worn-through bushings and flattened sprockets for thousands of hours without incident—especially on flat terrain.
However, caution is advised when working on slopes or uneven ground. Worn rails can allow the track to slip off rollers, causing sudden steering loss or stoppage. In such cases, lifting the affected side with the boom or blade may be necessary to reseat the track.
Link Count and Chain Stretching
Excavator chains stretch over time due to internal wear. To compensate, some operators remove a link from the chain to restore tension. This is acceptable for low-speed, low-load applications but should be done with care. Always verify the original link count from manufacturer specifications or dealer records before making adjustments.
If the idlers are still recessed within the track frame and the link count matches factory specs, the chain likely has usable life remaining. If the idlers are fully extended and the chain has extra links, it may be time to consider replacement or reconfiguration.
Seals, Lubrication, and Bridging Risk
Unlike crawler tractors, most excavators do not use sealed and lubricated track chains. Instead, grease is applied during assembly, and wear occurs externally and internally. Over time, lack of lubrication can lead to a condition called bridging—where links seize in a curved position and fail to straighten. Once this happens, the chain loses flexibility and may derail or bind.
To prevent bridging:

• Keep tracks clean of mud and debris
  
• Avoid prolonged idle storage in wet conditions
  
• Monitor articulation during travel and turning
  

Accelerated Wear After 50% Threshold
Undercarriage wear does not progress linearly. Once components reach 50% wear, the rate of degradation often accelerates due to reduced surface hardness and increased friction. This is especially true for pins and bushings, which lose their hardened layer and begin to deform under load.
Recommendations:

• Inspect undercarriage quarterly for machines used seasonally
  
• Replace bushings or pins individually if localized wear is found
  
• Use wear indicators or calipers to measure link height and roller diameter
  
• Keep tensioners within mid-stroke range to avoid overextension
  

Cost Considerations and Practical Advice
Replacing a full undercarriage can cost more than the value of an older machine. For low-hour users, the goal should be to maintain functionality rather than restore factory condition. If the tracks stay on, the machine moves reliably, and the work is light, it’s often better to run the undercarriage until failure becomes frequent.
In Manitoba, a farmer operated a used excavator with worn tracks for over 2,500 hours before removing a link. After adjustment, the machine continued to perform for another 1,500 hours without derailment. He kept spare rollers and idlers on hand but never needed to install them.
Conclusion
Undercarriage wear on excavators is a nuanced topic, especially for low-hour users in agricultural settings. While manufacturers provide precise wear metrics, real-world conditions allow for flexibility. By understanding wear indicators, link behavior, and terrain impact, operators can make informed decisions—balancing cost, safety, and performance.
For light-duty work, a worn undercarriage is not a death sentence. With proper tension, awareness of slope limitations, and periodic inspection, even an old machine can keep digging, lifting, and hauling for years to come.