A mounted bearing on a conveyor. Maintenance replaces it with the same model.

A few weeks later, it fails again.

The bearing is upgraded. Lubrication schedules are adjusted. Alignment is checked. Yet the problem keeps coming back.

In many cases, the issue isn’t that the bearing was too small or poorly manufactured. It’s that the bearing was designed for a different type of load than the application was actually producing.

Every bearing is subject to force, but not every force acts in the same direction. Some forces act perpendicular to the shaft (radial loads), while others push or pull along the shaft’s centerline (axial, or thrust, loads). Most industrial equipment operates under a combination of both.

Understanding the difference between axial vs. radial loads is essential for selecting the right mounted bearing, diagnosing bearing damage, and improving equipment reliability. Whether you’re working with conveyors, gearboxes, fans, crushers, bucket elevators, or screw conveyors, recognizing how these load directions affect a bearing can help reduce unplanned downtime and extend service life.

In this article, you’ll learn:

• What axial and radial loads are
• How load direction affects bearing performance and service life
• Common bearing damage caused by excessive axial loads
• How different mounted bearing designs handle radial and axial loads
• General considerations when matching mounted bearings to the application

What Are Axial and Radial Loads?

Every rotating shaft is subject to forces during operation. These forces are generally categorized as either radial loads or axial loads, depending on the direction they act on the shaft. Understanding the difference between axial vs. radial loads is one of the first steps in selecting the right mounted bearing, diagnosing bearing damage, and improving equipment reliability. and improving equipment reliability.

What Is an Axial Load?

An axial load, also called a thrust load, is a force that acts parallel to the shaft. Instead of pushing perpendicular to the shaft, it pushes or pulls along the shaft’s centerline.

A simple way to visualize an axial load is to imagine pushing on the end of a steel rod. The force travels straight through the rod from one end to the other. The same principle applies to a rotating shaft when thrust forces act along its axis.

In industrial equipment, axial loads commonly occur when components generate thrust or when shafts move slightly during operation. Common examples include:

• Screw conveyors moving material along the length of the screw
• Gearboxes that generate thrust forces during operation
• Pumps and fans that create axial thrust on the shaft
• Thermal expansion that causes shafts to grow as temperatures increase

When significant axial forces are present, the bearing must be designed to carry that thrust load without creating excessive stress on the rolling elements or raceways.

What Is a Radial Load?

A radial load is a force that acts perpendicular to the shaft. Rather than pushing or pulling along the axis of the shaft, it pushes against the radius of the shaft.

Imagine a belt-driven conveyor or electric motor. As the belt pulls on the drive pulley, it creates a radial force that the mounted bearing must support.

Radial loading is the most common loading condition found in rotating equipment. Typical examples include:

• Belt tension on conveyor pulleys
• The weight of rotating shafts and pulleys
• Chain drives
• Wheels and axles supporting vehicle loads

Because radial loads are present in so many industrial applications, many mounted bearings are designed primarily to support radial loading while also accommodating light-to-moderate axial loads.

Axial vs. Radial Loads: Quick Comparison

Axial Load	Radial Load
Acts parallel to the shaft	Acts perpendicular to the shaft
Pushes or pulls along the shaft	Pushes against the radius of the shaft
Often called thrust load	Commonly created by belt tension or equipment weight
Common in screw conveyors, pumps, gearboxes, and fans	Common in conveyors, pulleys, and chain drives
Requires bearings designed to handle thrust loads	Requires bearings designed primarily for radial loads

In practice, bearings rarely experience only one type of load. Most industrial equipment operates under combined radial and axial loads, making it essential to understand how these forces interact and affect bearing performance.

Most Industrial Equipment Experiences Combined Loads

Although it’s helpful to discuss axial and radial loads separately, most industrial equipment operates under combined loading conditions. Bearings rarely experience only one type of force.

For example, a screw conveyor supports radial loads from the weight of the screw and the material being conveyed while simultaneously generating axial (thrust) loads as material moves through the trough.

Likewise, a conveyor pulley primarily experiences radial loads from belt tension, but shaft misalignment, thermal expansion, and structural movement can also introduce axial forces.

Because most applications involve combined radial and axial loads, bearing selection involves more than matching a load rating. Maintenance professionals and engineers must consider the direction, magnitude, and combination of forces acting on the bearing to maximize reliability and service life.

Common Bearing Damage Caused by Axial Loads

Not every axial load causes bearing damage. In fact, many mounted bearings are designed to handle a certain amount of axial loading during normal operation.

Problems arise when thrust loads exceed the bearing’s design limits or occur alongside other factors such as misalignment, contamination, shock loading, or inadequate lubrication. Over time, these conditions can accelerate wear, increase vibration and operating temperatures, and ultimately shorten bearing service life.

Recognizing common bearing failure modes can help maintenance teams identify the root cause before repeated failures occur.

Ball Bearing

A ball bearing may exhibit wear patterns caused by race edge loading, including fatigue spalls or GSC spalls.

Spherical Roller Bearing

A spherical roller bearing may exhibit one set of rolling elements that is loaded and the other that is unloaded. This can result in premature cage damage and/or roller skidding/adhesive wear on the unloaded rollers/race.

Cylindrical Roller Bearing

A cylindrical roller bearing may exhibit excessive rib/roller end wear from excessive thrust load. This may appear as rib discoloration caused by excessive heat or as excessive axial movement resulting from rib wear. 

Common Causes of Bearing Failure 

The damage patterns discussed above—such as spalling, brinelling, and false brinelling—rarely occur in isolation. In most cases, they result from one or more underlying conditions that place excessive stress on the bearing.

When diagnosing a bearing failure, evaluate the entire application rather than focusing only on the damaged bearing itself.

The most common causes of bearing failure include:

• Excessive axial loads that exceed the bearing’s design capacity
• Improper bearing selection, such as using a bearing that isn’t designed for the application’s loading conditions
• Improper installation or incorrect bearing adjustment
• Shaft or housing misalignment that creates uneven load distribution
• Inadequate, incorrect, or contaminated lubrication
• Moisture, dust, or debris entering the bearing
• Shock loading and repeated impact forces

These factors often occur together. For example, a mounted bearing operating under moderate thrust loads may provide years of reliable service under clean, well-aligned conditions. However, adding contamination, poor lubrication, misalignment, or repeated shock loading can significantly shorten bearing life.

Understanding the root cause of a bearing failure helps ensure the replacement bearing matches the application’s actual operating conditions—not simply replacing it with the same bearing that failed.

How Axial and Radial Loads Influence Bearing Selection

The direction of the load on a bearing helps determine which bearing design best suits the application.

Different mounted bearing designs are engineered to handle different combinations of radial loads, axial loads, shock loading, contamination, shaft misalignment, and operating conditions. Selecting the right bearing means evaluating the complete application—not simply matching a load rating.

As a general guideline:

• Mounted ball bearings are commonly used for applications dominated by radial loads with light-to-moderate thrust.
• Mounted spherical roller bearings are well-suited for heavy radial loads, combined loading, shock, contamination, and shaft misalignment.
• Mounted tapered roller bearings are often selected where significant axial thrust and precise shaft positioning are required.

The table below provides general guidance for matching common industrial applications with the mounted bearing types most often used to support their operating conditions.

Application	Typical Conditions / Loads	Recommended Mounted Bearing Type	Recommended Seals / Housing	Short Justification
Crushers (jaw, cone, impact)	Heavy radial loads, shock/impact, misalignment, heavy contamination	Mounted spherical roller bearings (primary); mounted tapered roller bearings (when controlled axial positioning needed)	Cast/steel housings, multi-point seals, grease purge	Spherical rollers handle heavy radial shock and misalignment; robust housings and seals reduce contamination-induced spalling. Use tapered mounted units only when axial control is required.
Ball mills / vertical roller mills	Very heavy radial loads, high contact stresses, abrasive dust, high temp, combined axial components	Mounted spherical roller bearings (primary); mounted tapered roller bearings at thrust/gearbox interfaces	Heavy-duty housings, multi-lip seals, grease purge, thermal-capable materials	Spherical rollers tolerate heavy radial load and misalignment; tapered units manage thrust where precise axial control is needed. Seals and purge combat abrasive dust.
Conveyors & bucket elevators	Radial from pulleys, occasional axial (belt tracking), heavy contamination, trapped bearings	Mounted spherical roller bearings (head/tail); mounted tapered roller bearings (take-up/tension shafts); mounted ball bearings (light idlers)	Housings with labyrinth or multi-lip seals, end covers, grease purge options	Spherical rollers resist misalignment and contamination in hard-to-access spots; tapered units control axial position; ball units OK for low-duty idlers.
Kilns, rotary dryers, trunnion supports	Significant combined radial + axial (thrust), thermal expansion, high temp, shock	Mounted tapered roller bearings for thrust supports; spherical mounted units for heavy radial supports	High-temp housings, sealed arrangements, paired tapered sets for axial control	Tapered rollers are suited for combined thrust/radial loads and axial positioning; spherical units handle misalignment where thrust is lower.
Fans & blowers (>50 HP, vertical shafts)	Mixed radial + sustained axial thrust, vibration, dust	Mounted tapered roller bearings (for thrust); mounted spherical roller bearings (if radial shock/misalignment dominate); sealed ball inserts (light duty)	Sealed housings, multi-point seals, shaft guards	For sustained axial thrust (vertical shafts) choose tapered rollers; spherical if heavy radial shock; proper sealing reduces contamination and skidding.
Gear drives / pinion shafts	Combined radial & axial from gear mesh, thin lubricant film risks, possible misalignment	Mounted tapered roller bearings (gear/pinion supports); mounted ball bearings for light gearboxes	Sealed housings, precision locking/preload methods, grease retention	Tapered rollers manage combined loads and gear thrust; correct preload/locking prevents seating/fretting issues and premature spalling.
Wet/slurry / abrasive conveyors	Abrasive, wet, corrosion risk, radial loads with occasional axial	Mounted spherical roller bearings (prefer corrosion-resistant/coated housings)	Multi-lip seals, corrosion-resistant housings, grease purge	Spherical rollers with sealed housings survive abrasive/wet service better; ball or tapered units need rigorous sealing to avoid rapid wear.
Light-duty idlers, feeders, low-speed shafts	Low radial loads, minimal axial forces, cleaner conditions	Mounted ball bearings (insert style)	Standard sealed inserts or light labyrinth seals	Ball-mounted units are economical and simple to service for light-duty applications; avoid over-specifying costly rollers.

While every application is unique, understanding how combined radial and axial loads affect bearing performance helps maintenance teams make more informed bearing selection decisions and improve equipment reliability.

Conclusion

Bearings do not fail simply because they carry heavy loads. More often, they fail because the type of load acting on the bearing wasn’t fully understood.

Recognizing the difference between radial and axial loads—and understanding when both are present—helps maintenance teams make better decisions during troubleshooting, equipment design, and bearing replacement. It also explains why two seemingly similar applications can require very different bearing solutions.

When load direction, operating conditions, and bearing design are properly matched, the benefits extend far beyond longer bearing life. Facilities can reduce unplanned downtime, improve equipment reliability, lower maintenance costs, and increase overall productivity.

While understanding load direction is an important first step, selecting the right bearing also requires considering factors such as shaft misalignment, contamination, lubrication, operating speed, and maintenance requirements. Evaluating the complete application helps ensure the selected bearing is suited to the actual operating environment, rather than being chosen solely on load rating.

Why Choose Timken Mounted Bearings?

For applications involving radial loads, axial thrust, or a combination of both, Timken mounted bearings offer a wide range of solutions designed for demanding industrial environments.

From mounted ball bearings for general-purpose applications to spherical roller bearings for heavy-duty service and tapered roller bearings for high-thrust applications, Timken engineers its bearing solutions to address the real-world operating conditions maintenance teams face every day. Advanced sealing options, multiple locking methods, and robust housing designs help improve bearing performance in applications where contamination, combination loading, and misalignment are common.

At IBT Industrial Solutions, we work with customers every day to help identify the causes of premature bearing failure and recommend mounted bearing solutions that fit the application—not just the specifications. Whether you’re replacing a single bearing or evaluating an entire conveyor, processing line, or power transmission system, our bearing specialists can help you select the right solution for long-term reliability.

Whether you’re replacing a damaged mounted bearing or designing new equipment, IBT’s bearing specialists can help evaluate your application and recommend the right Timken mounted bearing for long-term reliability.