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The Treefarmer Grapple Skidder and Its Role in Logging
The Treefarmer Grapple Skidder, particularly the 1987 model referenced in this discussion, was a staple in North American logging operations during the late 20th century. Built for durability and brute pulling power, Treefarmer machines were designed to drag logs from forest stands to landing zones with minimal mechanical complexity. The 24.5x32 20-ply tires mounted on the rear axle were chosen for their high load capacity and resistance to puncture in rugged terrain.
Treefarmer, originally a Canadian brand, gained popularity in the U.S. through its straightforward design and affordability. By the late 1980s, thousands of units were in service across the Midwest and Appalachia, often operated by small crews with limited budgets. The machines typically featured open differentials, mechanical winches, and basic hydraulic systems—ideal for remote logging sites.
The Impact of Uneven Tire Wear
Running one rear tire with 50% tread and the other nearly bald raises concerns about drivetrain stress and traction imbalance. In a four-wheel-drive system, especially on hard surfaces, mismatched tire diameters can cause differential binding. This occurs when the rotational speed between axles or wheels differs, forcing the transfer case or axle shafts to absorb the mismatch.
However, in soft terrain—mud, snow, or loose soil—slippage mitigates this effect. The bald tire may spin more easily, reducing stress on the drivetrain. On hard ground, such as gravel roads or frozen soil, the lack of slippage can lead to overheating in the transfer case or premature wear in the axle bearings.
Differential Types and Their Influence
The severity of the issue depends on the type of differential:
Terminology Notes
Loggers often operate with mismatched tires due to cost constraints. One operator reported that replacing a single tire took 12 hours, while the second took only six—highlighting the labor involved. In regions like Ohio and the Carolinas, it’s common to see skidders with one new tire and one worn-out one, especially during peak logging season when downtime is costly.
To monitor drivetrain stress, some operators use infrared temperature guns to check bearing temperatures on the transfer case. A spike in temperature may indicate binding. If readings remain normal, the machine is likely operating within safe limits.
Recommendations for Operators
Conclusion
Running a Treefarmer skidder with uneven rear tires is not ideal, but it’s often a practical necessity in the logging industry. With open differentials and soft terrain, the risk of mechanical damage is low—provided operators remain vigilant. By understanding the dynamics of tire wear and drivetrain stress, crews can extend the life of their machines while managing costs effectively.
The Treefarmer Grapple Skidder, particularly the 1987 model referenced in this discussion, was a staple in North American logging operations during the late 20th century. Built for durability and brute pulling power, Treefarmer machines were designed to drag logs from forest stands to landing zones with minimal mechanical complexity. The 24.5x32 20-ply tires mounted on the rear axle were chosen for their high load capacity and resistance to puncture in rugged terrain.
Treefarmer, originally a Canadian brand, gained popularity in the U.S. through its straightforward design and affordability. By the late 1980s, thousands of units were in service across the Midwest and Appalachia, often operated by small crews with limited budgets. The machines typically featured open differentials, mechanical winches, and basic hydraulic systems—ideal for remote logging sites.
The Impact of Uneven Tire Wear
Running one rear tire with 50% tread and the other nearly bald raises concerns about drivetrain stress and traction imbalance. In a four-wheel-drive system, especially on hard surfaces, mismatched tire diameters can cause differential binding. This occurs when the rotational speed between axles or wheels differs, forcing the transfer case or axle shafts to absorb the mismatch.
However, in soft terrain—mud, snow, or loose soil—slippage mitigates this effect. The bald tire may spin more easily, reducing stress on the drivetrain. On hard ground, such as gravel roads or frozen soil, the lack of slippage can lead to overheating in the transfer case or premature wear in the axle bearings.
Differential Types and Their Influence
The severity of the issue depends on the type of differential:
- Open Differential
Allows wheels to rotate at different speeds. Uneven tires cause less mechanical stress but may reduce traction.
- Locking Differential
Forces both wheels to rotate together. Mismatched tires can lead to binding and potential shaft damage.
- Limited Slip Differential
Uses clutches or gears to balance torque. Uneven tires may confuse the system, causing erratic behavior.
Terminology Notes
- Differential Binding: Mechanical stress caused by unequal wheel rotation in a drivetrain.
- Transfer Case: A gearbox that splits power between front and rear axles in four-wheel-drive systems.
- Ply Rating: Indicates tire strength and load capacity; 20-ply tires are extremely robust.
- Slippage: Loss of traction that allows wheels to rotate freely, reducing drivetrain stress.
Loggers often operate with mismatched tires due to cost constraints. One operator reported that replacing a single tire took 12 hours, while the second took only six—highlighting the labor involved. In regions like Ohio and the Carolinas, it’s common to see skidders with one new tire and one worn-out one, especially during peak logging season when downtime is costly.
To monitor drivetrain stress, some operators use infrared temperature guns to check bearing temperatures on the transfer case. A spike in temperature may indicate binding. If readings remain normal, the machine is likely operating within safe limits.
Recommendations for Operators
- Avoid long-distance travel on hard surfaces with mismatched tires
- Monitor transfer case and axle temperatures during operation
- Replace tires in pairs when possible, especially on locking differential machines
- Use tire chains on worn tires to improve traction and balance
- Inspect axle shafts and bearings regularly for signs of wear
Conclusion
Running a Treefarmer skidder with uneven rear tires is not ideal, but it’s often a practical necessity in the logging industry. With open differentials and soft terrain, the risk of mechanical damage is low—provided operators remain vigilant. By understanding the dynamics of tire wear and drivetrain stress, crews can extend the life of their machines while managing costs effectively.
