Proper Track Adjustment on Komatsu Excavators for Longevity and Performance

[MikePhua]

Why Track Tension Matters in Undercarriage Health
Track tension is one of the most overlooked yet critical aspects of excavator maintenance. On Komatsu machines, especially mid-size models like the PC200 and PC220 series, improper track adjustment can lead to accelerated wear, increased fuel consumption, and even undercarriage failure. Tracks that are too loose risk derailing during travel or digging, while overly tight tracks strain the final drives, idlers, and rollers.
Komatsu’s undercarriage design relies on a grease-filled hydraulic adjuster to maintain proper tension. This system allows for easy field adjustment without the need for external tools, but it also requires regular inspection and understanding of soil conditions, operating habits, and machine load.
Understanding the Track Adjustment Mechanism
Komatsu excavators use a grease cylinder located behind the front idler. When grease is pumped into the cylinder, it pushes the idler forward, tightening the track. Releasing grease via a relief valve retracts the idler, loosening the track.
Key components include:

• Track adjuster cylinder
  
• Front idler
  
• Relief valve (usually a hex bolt with a locking nut)
  
• Grease fitting and zerk
  
• Track links and bushings
  

The system is simple but effective. However, if the relief valve is damaged or the grease fitting is clogged, adjustment becomes difficult or impossible.
Recommended Track Sag and Measurement Procedure
Komatsu recommends checking track sag with the machine parked on level ground and the track lifted off the surface using the boom and arm. The standard sag measurement is taken from the bottom of the carrier roller to the top of the track chain.
Typical sag values:

• For standard-duty applications: 30–40 mm (1.2–1.6 inches)
  
• For heavy-duty or rocky terrain: 20–30 mm (0.8–1.2 inches)
  
• For soft or muddy ground: up to 50 mm (2 inches) to reduce packing
  

Measurement steps:

• Lift one side of the track off the ground
  
• Place a straight edge across the carrier roller
  
• Measure the vertical distance from the straight edge to the top of the track chain
  
• Adjust as needed using the grease fitting or relief valve
  

A contractor in British Columbia once reduced his undercarriage replacement frequency by 40% after adopting a monthly sag check routine across his fleet.
Signs of Improper Track Tension
Symptoms of loose tracks:

• Track jumping or derailing during turns
  
• Excessive wear on sprocket teeth and bushings
  
• Slapping noise during travel
  
• Uneven wear on rollers and carrier wheels
  

Symptoms of tight tracks:

• Increased fuel consumption
  
• Idler bearing failure
  
• Hydraulic adjuster seal leakage
  
• Cracked track links or pins
  

In one case, an operator in Queensland ran his PC210 with overtightened tracks for six months. The result was a failed idler bearing and a $3,000 repair bill. After training his crew on proper tensioning, the issue never recurred.
Grease Cylinder Maintenance and Troubleshooting
If the track won’t adjust:

• Check the grease fitting for blockage
  
• Inspect the relief valve for damage or corrosion
  
• Verify that the idler moves freely and isn’t seized
  
• Look for leaks around the cylinder seals
  

If the relief valve is stripped or missing, it must be replaced. Some operators fabricate temporary plugs, but this can lead to uncontrolled grease release or contamination.
Preventive tips:

• Clean the grease fitting monthly
  
• Use high-pressure grease rated for heavy equipment
  
• Replace seals every 2,000 hours or during undercarriage overhaul
  
• Avoid over-pumping grease—stop when sag reaches spec
  

Environmental Factors and Seasonal Adjustments
Track tension should be adjusted based on operating conditions:

• In winter, frozen mud can pack between links, requiring looser tension
  
• In summer, dry soil may cause shrinkage, allowing tighter settings
  
• In swampy terrain, looser tracks reduce strain and prevent derailment
  

Operators should inspect track sag weekly in variable conditions. A forestry crew in Oregon developed a seasonal checklist that included track tension, resulting in fewer derailments and smoother travel in mixed terrain.
A Story from the Field
In 2019, a pipeline crew in Alberta noticed that their Komatsu PC220 was derailing frequently during side-slope trenching. After inspection, they found the track sag exceeded 70 mm due to a failed grease fitting. The idler had retracted fully, and the relief valve was jammed with clay. After replacing the fitting and flushing the valve, they restored proper tension and completed the project without further issues.
Conclusion
Track adjustment on Komatsu excavators is not just a maintenance task—it’s a performance safeguard. By understanding the grease cylinder system, measuring sag accurately, and adapting to terrain, operators can extend undercarriage life and reduce operating costs. In the world of tracked machines, tension is balance—and balance keeps the iron moving.