Radial vs. Axial Load: How to Choose the Right Bearing

Radial and axial loads apply force in different directions, and using the wrong bearing type can lead to premature wear, system inefficiencies, or failure.

Understanding these fundamental forces is key to selecting the right bearings, improving system performance, and extending component lifespan.

Whether you're troubleshooting failure points or optimizing custom bearing designs, this article will help unravel the complexities of bearing loads so you can make informed decisions.

Understanding Radial Loads

Radial load is one of the most common and one of the two primary force directions that bearings must accommodate, the other being axial load.

Selecting the correct bearing type and accommodating radial forces is essential for maintaining performance, reducing wear, and ensuring system durability.

What is Radial Load?

Radial load is a type of centrifugal force acting perpendicularly to the axis of a rotating shaft or component, directed towards its center.

In bearings, it's the load carried at right angles to the rotation axis.

What Causes Radial Load?

Radial load most often comes from the weight of the rotating parts themselves — a shaft, gear, or pulley pressing down under gravity. It also builds up from rotating imbalance and vibration, since any uneven mass distribution creates a centrifugal force that pushes outward as the shaft spins.

Belt and chain drives add another source: the tension needed to transmit power creates a sideways pull on the shaft, perpendicular to its centerline. Shaft misalignment can amplify all of these, since a shaft that isn't running true adds extra perpendicular force on top of the load the bearing was designed for.

Examples of Radial Load Applications

Radial loads are typical in rotating applications such as car wheels, machine shafts, electric motors, pulleys, and gearboxes.

For example, a car's wheel bearings experience varying radial loads dependent on the vehicle's speed and weight.

How Radial Load is Transferred Through the Bearing

In a bearing subjected to radial load, the load is transferred from the inner raceway through the rolling elements (balls or rollers) to the outer raceway.

The force is distributed over several rolling elements simultaneously, depending on the bearing design and the size of the load.

Impact of Radial Load Distribution on Rolling Elements

Radial load distribution impacts bearing performance and longevity.

Proper distribution prevents over-stressing individual elements, ensuring balanced wear.

However, uneven distribution can cause premature bearing failure due to excessive stress on certain elements.

Suitable Bearing Types for Handling Radial Load

Various bearings handle radial loads, including deep groove ball bearings for their versatility, cylindrical roller bearings and needle roller bearings for heavy loads, and self-aligning ball bearings for misalignment scenarios.

Each type is selected based on the application and load magnitude.

Understanding Axial Load

Unlike radial loads that push perpendicular to the shaft, axial loads push or pull in line with the shaft's centerline.

These forces are crucial to consider when designing components that experience significant end-to-end pressure, as choosing the wrong bearing for axial forces can lead to decreased efficiency, faster wear, or premature failure.

What is Axial Load?

Axial load, synonymous with thrust or parallel load, is the force that acts parallel to the shaft's axis.

Simply put, it's a force that's exerted along the lines of the center, or axis, of an object.

For a deeper dive, see our full guide on axial load.

What Causes Axial Load?

Axial load typically comes from a process force acting straight along the shaft — the weight of a vertical shaft and its rotating parts pressing down under gravity, the thrust from a pump impeller or fan pushing back against the flow it's moving, or the reaction force from a screw drive or gear mesh (helical and bevel gears in particular generate a thrust component as they turn).

Thermal expansion is another common source: as a shaft heats up during operation, it grows in length, and if that growth is constrained, it pushes axially against the bearing. Acceleration and braking forces along the direction of travel, such as in a vehicle axle, are a further source of axial load.

Examples of Axial Load Applications

Axial loads are prevalent in various sectors, including automotive axles, aerospace jet engines, wind turbines, and industrial conveyor systems.

They also occur in pumps and compressors, and screw drive systems due to forces exerted by fluid, gas, or mechanical movement.

How Axial Load is Transferred through the Bearing

Axial load transfers through a bearing's raceways and rolling elements.

In thrust ball bearings, the load passes from one washer to another via balls aligned parallel to the rotation axis, enabling high axial load capacity.

Tapered roller bearings handle axial and radial loads, with their tapered design facilitating axial load transfer along inclined surfaces, thereby improving load distribution and reducing stress.

Balanced Load Distribution in Axial Load Scenarios

Achieving balanced load distribution in axial load scenarios is key for optimal bearing performance, durability, and smooth operation.

Ideally, axial loads are equally shared among all rolling elements, minimizing wear and enhancing bearing efficiency.

Factors such as misalignment or uneven loading can disrupt this balance, increasing stress and potentially leadinng to premature failure.

Suitable Bearing Types for Handling Axial Load

Thrust bearings are the go-to choice for handling axial loads due to their design that accommodates forces parallel to the axis.

Types include thrust ball bearings for lighter loads and thrust roller bearings for heavier loads.

Angular contact ball bearings can manage combined radial and axial loads, provided the axial component is significant.

Comparison of Radial Load and Axial Load

Differentiating between radial and axial loads, or understanding the concept of radial vs axial load, is vital for the optimal selection and use of bearings.

The primary distinctions lie in the direction of the force applied - radial loads act perpendicular to the shaft's axis, and axial loads act parallel to it.

The type of bearing used also varies between these loads.

While deep-groove ball bearings are better equipped to handle radial loads, thrust ball bearings are designed for axial loads.

However, it's essential to note that most bearings, such as angular contact ball bearings, can handle both radial and axial loads.

For a more comprehensive understanding, let's look at a comparative table:

Combined Loads in Real-World Applications

In most situations, bearings aren't subjected to just radial or just axial forces, but rather a combination of both (sometimes, moment loads as well).

These combined loads require bearings that can handle forces from multiple axial directions at the same time, so careful selection, load calculations, and engineering are needed.

What Is a Combined (Combination) Bearing?

A combined bearing is a compound roller unit that pairs a needle or cylindrical roller row for radial load with a separate angular contact or tapered roller row for axial load, built into a single stud-mounted housing. Unlike a standard track roller, which relies on a crowned outer ring to tolerate only minor axial loads, a combined bearing has a dedicated row of rolling elements for each direction, so it can support meaningful radial, axial, and even tilting (moment) loads at the same time.

They're commonly used in pairs along a guide rail — a combined bearing on one rail face, and a radial-only roller such as precision radial roller bearings on the opposing face — in applications such as crane systems, warehouse stacker cranes, elevator guide rails, and forklift masts. Adjustable variants, using an eccentric stud or shims, let the roller pair be fine-tuned to remove play against the rail.

LILY Bearing supplies a full range of combined bearings, including standard, eccentric adjustable, heavy duty, and shim-adjustable configurations for guide-rail applications that need both radial and axial support in a single compact unit.

Angular contact ball bearings and tapered roller bearings are examples of bearings designed to handle dual forces.

Understanding combined loads is key in applications like automotive wheel hubs, industrial gearboxes, and turbines, where unbalanced or mis-calculated forces can cause premature wear and failure.

There are also non-roller style bearings (i.e., telescopic rails) with individual balls that move along their surface.

These are most commonly used for cabinet drawers and machinery that extends and retracts loads during operation.

How Load Type Affects Bearing Life

The type of load (i.e., radial, axial, or a combination) determines which bearing is best for a given application.

Bearings are engineered for specific load directions and capacities, so selecting the wrong one can result in reduced performance or failure.

For example, deep groove ball bearings handle mostly radial loads but can handle some axial loads, while angular contact bearings are for applications where both radial and axial loads are high.

Matching load to bearing design is critical for system reliability, safety, and longevity.

Radial Load Ratings vs. Axial (Thrust) Load Ratings

Bearing catalogs publish a dynamic and a static load rating for radial load, usually labeled Cr and C0r. For bearings that also carry some axial load, such as deep groove ball bearings, manufacturers often list a separate allowable axial load figure — sometimes labeled Ca or C0a — that caps how much thrust the same bearing can take on top of its primary radial duty, typically a fraction of its radial rating.

Purpose-built thrust bearings flip this around: their dynamic and static axial ratings are the primary spec, since carrying axial load is what they're designed to do. When comparing bearings for a combined-load application, checking both the radial and axial rating — not just one — is the only way to confirm the bearing will hold up under the actual mix of forces it will see in service.

That said, load direction is only part of the equation. Whether a bearing is in motion or stationary when the load is applied matters just as much — and that's where static and dynamic load ratings come in.

For a closer look at how these ratings work and how to calculate bearing life, see our guide on static load vs dynamic load in bearings.

Practical Considerations

Assessing radial and axial loads in real-world applications demands attention to various aspects such as operating speed, load magnitude and direction, and the operating environment.

Carefully balancing these loads can lead to a noticeable improvement in bearing performance and life.

A case study worth mentioning is in the realm of automotive wheel bearings.

These bearings need to handle both radial loads (from the vehicle's weight) and axial loads (from cornering forces).

The delicate balance and distribution of these loads are crucial for the smooth and efficient operation of the vehicle.

Additionally, the bearing's material selection, like Chrome Steel or Stainless Steel, also plays a significant role in handling radial and axial loads.

Chrome Steel, for instance, is often used for its high load capacity and wear resistance, making it suitable for applications with high radial and axial loads.

Choosing the Right Bearings for Radial, Axial, and Combined Loads

Understanding and managing radial vs axial load can greatly enhance bearing performance and longevity.

Selecting the right bearing, based on the load nature, can boost your machinery's efficiency.

At LILY Bearing, we provide a wide range of bearings to meet varied load needs.

Our expertise and quality commitment assure optimal performance and extended machinery life through our tailored bearing solutions.

Explore our full selection of bearings designed for radial, axial, or combined load support.

Frequently Asked Questions

What does axial vs radial mean?

Axial means a force acting parallel to a shaft's centerline, pushing or pulling along its length. Radial means a force acting perpendicular to that centerline, pointed toward or away from the shaft. The two terms describe force direction, not force size — a shaft can carry a large amount of both at once.

What is the difference between radial and axial load?

The main difference is direction. Radial load acts perpendicular to the shaft's axis — think of the force pushing outward from the center of a spinning wheel.

Axial load, on the other hand, acts parallel to the shaft's axis, pushing or pulling along its length.

In practice, most machines deal with both at the same time, which is why bearing selection matters so much.

What bearings are used for radial loads?

Deep groove ball bearings are the most common choice — they handle radial loads well and can take on moderate axial loads too, which makes them versatile for everyday applications.

For heavier radial loads, cylindrical roller bearings or needle roller bearings are better suited. If shaft misalignment is a concern, self-aligning ball bearings are worth considering.

What bearings are used for axial loads?

Thrust bearings are the go-to for purely axial loads. Thrust ball bearings work well for lighter applications, while thrust roller bearings handle heavier ones.

If the application involves significant axial load alongside radial load, angular contact ball bearings or tapered roller bearings are typically the better fit.

What is an example of axial load?

A common example is a vertical pump shaft, where the weight of the shaft and impeller presses straight down the shaft's axis onto a thrust bearing. Another is a car accelerating or cornering, where the wheel bearings absorb the thrust pushing along the axle.

Can a bearing handle both radial and axial loads?

Yes — and in most real-world applications, that's exactly what's needed. Angular contact ball bearings and tapered roller bearings are specifically designed for combined loads.

Even deep groove ball bearings can handle some axial load, though they're primarily radial bearings. The key is knowing the ratio of radial to axial force in your application before selecting a bearing.

Can ball bearings take axial loads?

Standard deep groove ball bearings can take a moderate amount of axial load in addition to their primary radial duty, typically a fraction of their radial rating. Where axial load is a major factor rather than a secondary one, angular contact ball bearings or thrust ball bearings are purpose-built to carry it.

What bearing is best for radial and axial load?

Angular contact ball bearings and tapered roller bearings are generally the best fit, since each has a row of rolling elements set at an angle to the shaft, letting a single bearing carry radial and axial force at the same time. Tapered roller bearings tend to suit heavier combined loads, while angular contact ball bearings suit higher speeds with moderate combined loads.

What is a combined bearing?

A combined bearing pairs a radial roller row with a separate angular contact or tapered roller row for axial load, built into one stud-mounted unit — rather than handling both loads through a single row of angled contact points the way angular contact or tapered roller bearings do. They're typically used in pairs along a guide rail, with a radial-only roller on the opposing face, in applications like crane systems, warehouse stacker cranes, and elevator guide rails where the rollers need adjustable preload against the rail.

What happens if you use the wrong bearing for the load type?

It usually shows up as premature wear, abnormal heat, noise, or unexpected failure — often well before the bearing's rated service life. A bearing designed for radial loads will struggle under sustained axial force, and vice versa.

Beyond the bearing itself, mismatched load handling can affect the whole system's efficiency and reliability. Getting the selection right from the start is almost always cheaper than dealing with the consequences later.