Heavy machines counterweights: functions and impact

In heavy machines, staying balanced isn’t something left to chance, it’s built into the design. Whether it’s an excavator digging, a crane lifting heavy things, or a forklift carrying loads, counterweights are what keep these machines steady and safe. 

In this article, we’ll explain what counterweights do, the different types used in heavy equipment, and how they help machines work better and safer.

What is a counterweight in heavy machines?

A counterweight is a heavy mass placed at the back or opposite side of a machine to balance the weight of the load being lifted or carried. When machines like excavators dig or cranes lift heavy objects, the counterweight helps keep them stable and prevents tipping or falling over. 

Without a properly sized counterweight, even a small load can make the machine unsafe to operate. 

Counterweights are carefully designed and positioned to improve safety, balance, and overall performance, making them a vital part of many types of heavy equipment including forklifts, wheel loaders, and cranes.

Why counterweights matter across machine types

Every type of heavy machine, from a compact forklift to a 500-ton crawler crane,  requires a unique counterweight system based on its intended use. Here's why:

1. Force balancing

Machines generate rotational forces during operation. When a boom or arm extends forward with a load, it creates a moment that must be counteracted. Counterweights balance these forces, reducing stress on the chassis and undercarriage, and improving operating precision.

2. Center of gravity

An optimal center of gravity (CG) improves maneuverability and safety. A rear-mounted counterweight helps shift the CG back toward the machine’s geometric center, minimizing the risk of tipping, especially in articulated loaders and tracked machines on inclines.

3. Tipping prevention

One of the most common causes of heavy equipment accidents is tipping. By increasing the machine’s resistance to forward or side overturn, counterweights allow operators to lift and transport heavier loads without sacrificing stability.

What are types of counterweights in heavy machines?

Counterweights vary not just in material and mass, but in form and flexibility. Here's a breakdown of the most commonly used types:

1. Fixed counterweights

These are integrated at the factory into the rear housing of the machine. Found on many standard excavators, dozers, and loaders, they offer simple, maintenance-free stability, though they reduce flexibility in transport weight.

2. Removable/modular counterweights

Common on mobile cranes, large wheel loaders, and telehandlers, these are designed to be detached for transport or weight balancing. Machines like the Liebherr LTM 1450-8.1 allow precise configuration of counterweight slabs depending on the job site.

3. Hydraulically adjustable counterweights

Seen on select medium to large excavators like the Komatsu PC490LC-11, this system allows the counterweight to shift backward or forward depending on the lift load, enhancing stability during operation and reducing transport width when retracted.

4. Smart/active counterweights

Primarily found in mobile cranes or electric forklifts, these use sensors and software to adjust weight dynamically. In machines like Linde’s E100 electric forklifts, electronic monitoring ensures optimal balance in real time.

Machine-specific breakdowns

Let’s examine how different heavy equipment types use counterweights, and why these configurations matter for performance and resale value.

• Excavators

Tracked and wheeled excavators rely heavily on rear-mounted fixed or hydraulically adjustable counterweights to offset boom extension and bucket weight. The counterweight mass is proportional to boom reach and lifting capacity. For example, the Volvo EC550 has a counterweight of approximately 10,600 kg, which helps it achieve a breakout force of around 251 kN. 

On makana.com, used units with intact OEM counterweights often show better structural balance and inspection grades.

• Cranes (crawler, mobile, tower)

Cranes require the most dynamic counterweight systems due to extreme lifting loads and long radii.

• Mobile cranes like the Grove GMK5250XL have slab-style counterweights totaling over 80,000 kg, and may include superlift counterweights for added rear leverage.

• Crawler cranes use stacked counterweights on the superstructure and may require counter-jibs.

• Tower cranes mount concrete counterweights on the counter-jib, carefully calculated against maximum load radius.

Counterweight configuration directly affects load charts, a crucial metric for crane buyers and inspectors.

• Wheel loaders

Wheel loaders, such as the Caterpillar 980M, incorporate fixed rear counterweights into the engine compartment area, helping offset the front axle load when the bucket is full. On larger units, optional rear counterweight kits can be added to enhance stability when using heavy attachments like log grapples or block forks. 

• Forklifts

Forklifts are counterbalanced machines by design. The rear counterweight, usually cast iron, balances the front load carried on forks.

• Internal combustion forklifts often feature large, fixed counterweights housing the engine.

• Electric forklifts use either lead-acid battery weight or add-on rear counterweights to achieve balance.

Incorrect or missing counterweights on used forklifts can compromise lift safety, an important consideration during inspection.

• Dozers and compact track loaders

Though less discussed, bulldozers and compact loaders may also use front or rear counterweights, especially when no blade or bucket is installed.

Counterweights help optimize traction and frame balance during ripper operation or when using non-standard attachments like trenchers or augers.

• Telehandlers

Telehandlers present unique stability challenges due to their telescoping booms and often elevated lifting heights.

OEMs like Manitou and JLG design modular counterweight systems that adapt to different boom lengths and attachments. Advanced models include adaptive load stability systems that actively adjust hydraulic pressure based on counterweight effectiveness.

Counterweight material and design

• Cast iron: Preferred for high-density needs and precision molding; commonly used in OEM configurations for excavators and cranes.

• Concrete: Cheaper but bulkier; often used in tower crane counter-jibs or aftermarket add-ons.

• Composite materials: Sometimes used in modern forklifts and specialized equipment for their strength-to-weight ratio.

Density, shape, placement

The shape of the counterweight must accommodate rear swing radius and engine clearance. Machines like the Hitachi ZX690LCH feature curved counterweights that maintain swing efficiency while housing ballast.

Proper placement (low and centered) ensures the counterweight contributes to overall machine balance, rather than introducing side lean or rear lift.

Conclusion

In every category of heavy equipment, from towering cranes to compact loaders, counterweights are foundational to safety and performance. Whether integrated, adjustable, or modular, their design impacts not just how a machine lifts, but how it drives, operates, and ages.

For buyers and sellers on makana.com, understanding counterweight configurations can clarify a machine’s condition, transport limitations, and job site capabilities. During inspections, checking for OEM compliance, physical integrity, and proper mounting is just as important as evaluating hours or hydraulics.

Counterweights may not move, but they make everything else move safely.