When purchasing casters, many companies calculate it this way:

The equipment has a total weight of 800 kg and is equipped with four casters, meaning each caster supports 200 kg. Simply select casters with a rated load capacity of at least 200 kg.

It may seem logically sound, but in reality, this is one of the most common misconceptions in caster procurement.

In actual operation, equipment is subjected not only to its static weight but also to dynamic loads, impact loads, and eccentric loads that constantly vary.

If you select casters solely based on their theoretical load capacity, even if they function properly, you may still encounter difficulties in pushing, reduced service life, frame deformation, or even safety hazards.

Truly professional selection never settles for “just enough”; instead, it thoroughly accounts for actual operating conditions and reserves an appropriate margin of load capacity for the casters.

The rated load capacity does not necessarily reflect the actual operating conditions.

Many people understand load capacity to mean “the maximum weight a caster can support.”

In practice, the rated load specified on a product is typically determined under relatively ideal conditions, such as uniform force distribution, a level floor, and moderate travel speeds.

However, real-world operating environments are often far more complex.

For example:

• A stroller generates an instantaneous impact when crossing a threshold.
• The ground has potholes, joints, or ramps;
• The equipment suddenly starts up or shuts down abruptly;
• Loading and unloading heavy objects causes the center of gravity to shift continuously.

All of these can cause the casters to instantly experience loads far exceeding their static weight capacity.

Therefore, when making purchasing decisions, it’s not enough to simply consider a device’s weight; you must also take into account how the device will be used.

Why don’t all four casters necessarily bear the load?

Many devices employ a four-wheel configuration, but this does not mean that the four casters always share the load evenly.

If the ground is slightly uneven, or if there are tolerances in the machining of the equipment’s base frame, one of the three wheels may be off the ground while the other two remain in contact.

Furthermore, when the equipment’s center of gravity is offset to one side, the casters closest to the center of gravity typically bear a greater load, while those farther from the center of gravity experience relatively less force.

Therefore, in practical applications, the load borne by a single caster often exceeds the theoretical average.

This is also why, on the same piece of equipment, some casters show severe wear while others remain almost as good as new.

Dynamic loads deserve more attention than static weight.

Imagine a cart loaded with equipment, at rest—its casters are subjected to steady, consistent pressure.

But when the device starts to move, the situation is entirely different.

At startup, static friction must be overcome;

When turning, the casters are subjected to lateral forces;

An instantaneous impact occurs when passing through the threshold;

During an emergency stop, inertia is again concentrated on the front caster.

The loads generated during these transient events are often greater than those experienced when the equipment is at rest.

For high-frequency mobile equipment, it is precisely these repeated dynamic loads—not the static weight—that truly put casters to the test.

Why does load capacity help extend the lifespan of casters?

Many people believe that as long as casters are not overloaded, their service life will remain unaffected.

In fact, operating continuously near the rated load capacity will likewise accelerate wear.

Prolonged high-intensity work can easily lead to several problems:

• The wear rate of the wheel tread accelerates;
• The bearing load increases, and the rolling resistance rises.
• When subjected to long-term compressive stress, the support is more prone to fatigue deformation.
• The gimbal’s rotation is no longer smooth;
• Resistance to implementation is gradually increasing.

If adequate load‑carrying margin is provided, the casters’ components will operate within a more optimal stress range over the long term, resulting in smoother overall performance and reduced maintenance frequency.

For equipment in long-term continuous use, this discrepancy will continue to grow over time.

Which scenarios should place greater emphasis on headroom?

For the following categories of equipment, it is recommended to prioritize actual operating conditions during selection, rather than relying solely on theoretical weight:

Logistics turnover equipment
Frequent daily movement, with numerous starts, stops, and turns, results in significant dynamic loads.

Mobile workbench
The tools and workpieces are constantly added or removed, resulting in significant weight fluctuations.

Automation equipment
The equipment demands high operational precision, and the stability of its casters directly affects overall performance.

Heavy-duty racking and mold carts
The concentrated load places higher demands on the long-term reliability of casters and brackets.

In these application scenarios, appropriately reserving sufficient capacity headroom is often more critical than simply pursuing the lowest procurement cost.

Before purchasing casters, it’s worth considering these key factors.

In addition to the equipment’s weight, it is also recommended to confirm the following in advance:

• Does the equipment need to be moved frequently every day?
• Do you frequently cross thresholds, ramps, or joints?
• Will the weight change with use?
• Is there a shift in the center of gravity?
• Is the operating environment level and dry?

These factors all influence the actual load conditions of casters and serve as critical criteria for professional selection.

Written at the end

The value of casters goes beyond simply “bearing weight”; more importantly, they must remain stable, durable, and safe over long-term use.

When making purchasing decisions, relying solely on a simple calculation based on equipment weight can easily overlook the additional loads imposed by actual operating conditions.

A truly mature selection approach involves a comprehensive evaluation across multiple factors—such as equipment weight, frequency of use, mode of mobility, and floor conditions—and ensures that the casters are designed with an appropriate load‑carrying margin.

This carefully selected caster system not only meets current requirements but also enables you to confidently address future operational challenges.

When purchasing casters, do you prioritize the rated load capacity or the actual operating conditions? Have you ever encountered a situation where “theoretical specs were sufficient, but the real‑world performance fell short”? Feel free to share your experiences in the comments and join the conversation about selecting the right casters.