Breakout Force and Tearout Force in Excavators: Definitions, Measurement, and Influencing Factors

Breakout force and tearout force are the two key measurements of an excavator's digging power. Breakout force refers to the force exerted at the bucket tip when using the stick cylinder, while tearout force (also called pryout) measures the force produced by the bucket cylinder. Both values directly influence how effectively an excavator can penetrate hard material, lift heavy loads, and maintain fuel economy during demanding work.

What Is Breakout Force?

Breakout force measures how much power can be exerted at the tip of the attached bucket or implement when curling towards the cab. A higher breakout force number translates to greater digging and lifting capability. In technical terms, it is the force at the bucket produced when using the stick cylinder—the hydraulic ram that drives the dipper arm.

Tearout force, by contrast, is the force at the tooth generated by the bucket cylinder. Both forces are typically expressed in kilonewtons (kN), a metric unit of work. One kilonewton equals 1,000 Newtons, where one Newton is the force required to accelerate one kilogram to one metre per second squared.

How Is Breakout Force Calculated?

Excavator manufacturers publish breakout force specifications calculated using accepted industry standards such as SAE J1179 or ISO 6015:2016. These calculations are typically based on a standard general-purpose bucket pinned directly to the excavator, without any quick coupler or attachment adapter in between.

The SAE J1179 standard relies on a mathematical simulation, whereas ISO 6015:2016 involves practical testing. Because of these different methodologies, measurements from the two standards can yield different results. Operators should always verify which standard a manufacturer has used when comparing specifications across brands.

Factors That Influence Breakout Force

Several design and configuration elements determine an excavator's breakout potential:

How Quick Couplers Reduce Breakout Force

Installing a quick coupler or any component that adds height between the dipper arm and the attachment reduces breakout force because it decreases mechanical advantage. A coupler increases the distance between the dipper pin and the bucket cutting edge, requiring greater force to overcome resistance at the end of the attachment.

Consider a comparison based on the SAE J1179 standard for three tilt motor couplers fitted to a 12-tonne machine. The Attach2 Heli-Tilt coupler, with a pin-to-pin height of 503 mm, achieves 153 kN of potential force. A competing coupler with 596 mm pin-to-pin height delivers 126 kN, while a third option at 623 mm height generates only 116 kN. The shorter coupler maintains 21 per cent more breakout potential over the first competitor and 32 per cent over the second.

That difference can be decisive when digging through compacted soil, rocky substrates, or frozen ground. It also affects fuel consumption: a machine working closer to its breakout limit consumes more diesel per cubic metre moved.

How to Improve Excavator Breakout Force

The simplest way to maximise breakout force is to install the shortest possible coupler and attachments. By minimising the distance between the dipper pin and the cutting edge—coupler height plus bucket height—operators can increase breakout force compared to taller configurations.

Using a squatter bucket design also reduces the height between the bucket pin and cutting edge, further boosting breakout potential. However, this approach compromises bucket capacity. Operators must weigh whether maximum breakout force or higher bucket volume better serves their productivity targets. In many earthmoving applications, a slightly reduced breakout force paired with greater bucket capacity delivers better cycle times and lower cost per tonne moved.

Machine Protection and Breakout Limits

Manufacturers set breakout force limits to suit each machine's size class and structural capacity. Relief valves open at predetermined pressure thresholds to protect the excavator from damage. Even if the hydraulic system is theoretically capable of higher breakout force, the relief valve prevents excessive pressure that could bend the boom, crack the dipper arm, or rupture hydraulic lines.

Operators should never adjust relief valve settings beyond factory specifications. Doing so voids warranties and exposes the machine to catastrophic failure. No excavator is incapable of damaging itself if operated outside design parameters, especially during prolonged heavy-duty work such as stump removal, rock excavation, or demolition.

Practical Implications for Fleet Managers

Understanding breakout force helps fleet managers match machines to job requirements. For general earthmoving and trench digging, a mid-range breakout force paired with optimal bucket capacity often delivers the best balance. For specialized tasks such as rock quarrying or large-diameter stump extraction, machines with higher breakout force and robust undercarriage components become essential.

When specifying attachments or evaluating quick coupler options, always request pin-to-pin height measurements and verify whether those figures include any offset. Shorter couplers preserve more of the machine's rated breakout force, translating to better performance without requiring a larger, more expensive excavator.

Soil type does not affect what the breakout force specification is—but it certainly determines how much of that available force the operator will need. Dense clay, frozen earth, and cemented glacial till all demand higher breakout force than loose sand or topsoil. Matching machine capability to site conditions minimises unproductive dogging, reduces fuel burn, and extends component service life.