If you’ve taken a close look at the structure of casters, you’ll notice an interesting phenomenon.

The wheels of a swivel caster are not mounted directly beneath the swivel plate; instead, they are offset from the axis of rotation.

This distance has a technical term in caster design— Offset 。

When selecting casters, many procurement professionals carefully compare wheel diameter, load capacity, and wheel tread material, yet they seldom pay attention to the offset distance.

However, it is precisely this unassuming dimension that determines whether a caster swivels easily, whether it is prone to shimmy, and how the handling feels over prolonged use.

What is the eccentricity?

Simply put, the eccentricity is… Horizontal distance between the rotational center axis of the swivel caster and the center of the wheel axle. 。

It is precisely because of this gap that the swivel casters can automatically adjust their orientation as the equipment moves forward, continuously keeping pace with its motion.

Without an eccentricity, the wheel would be unable to self‑align, and the universal joint function would lose its purpose.

It can be said that the eccentricity is the key design feature that enables casters to swivel smoothly.

Why can’t the eccentricity be designed to be zero?

Many people wonder: since a smaller offset brings the wheel closer to the bracket, wouldn’t that make the whole assembly more stable?

In fact, if the eccentricity is too small, although the caster’s structure becomes more compact, its self‑centering capability will be significantly reduced.

When the device first starts to move, the casters take longer to align properly, often resulting in a dragging sensation and even brief lateral slippage.

Moreover, an appropriate eccentricity allows the traction generated by rolling to guide the wheel into the correct orientation more quickly, resulting in smoother propulsion.

Therefore, the eccentricity is not an unnecessary dimension; rather, it is a critical factor enabling the swivel caster to achieve flexible steering.

Does a larger caster offset always result in lighter steering?

The answer isn’t that either.

As the eccentricity increases, the caster’s self‑steering capability is enhanced, and the rate of directional adjustment typically becomes faster.

However, at the same time, it also gives rise to new problems.

For example:

• The turntable’s rotation radius increases;
• Increased space occupation during steering;
• Flutter is more likely to occur at high speeds;
• Higher overall rigidity is required for the bracket.

Therefore, the design of eccentricity must strike a balance between flexibility and stability, rather than simply striving for greater values.

This is also why casters designed for different applications often have varying eccentricity designs.

What is the relationship between eccentricity and the riding experience?

Many users have had this experience:

Some casters can be steered with just a gentle nudge, while others feel as if they’re “twisting against you” every time you try to move them.

In addition to factors such as bearings and wheel materials, the eccentricity is also a significant contributing factor.

A properly sized eccentricity enables the caster wheel to adjust its direction more quickly and reduces starting resistance.

Especially in work environments with frequent turns and repeated changes of direction, operators will noticeably find pushing much easier.

This is especially important for equipment that requires frequent changes in direction, such as logistics carts, medical devices, and food-service trolleys.

Does the eccentricity affect the lifespan of casters?

Yes, and many people aren’t even aware of it.

If the eccentricity design is not compatible with the equipment’s operating conditions, the casters will experience increased lateral forces when adjusting their direction.

Over the long term, this can easily lead to:

• Wear on the universal swivel plate is accelerating;
• The stent gap gradually increases;
• Uneven bearing load;
• Abnormal wear has appeared on the wheel tread.

Therefore, the eccentricity not only affects how easily the caster can be pushed, but also impacts the long-term durability of the entire caster.

Do you need to pay attention to the eccentricity when making a purchase?

For typical light-load equipment, procurement personnel generally do not need to calculate the eccentricity separately.

However, for the following categories of equipment, it is recommended to place particular emphasis on the overall structural design:

• Automated logistics equipment;
• AGV auxiliary equipment;
• High-frequency moving workbench;
• Precision instrument trolley;
• Heavy-load transportation equipment.

These devices demand high levels of handling stability, and the rationality of the caster design is often more critical than any single parameter.

Therefore, rather than comparing eccentricity values in isolation, it is more prudent to assess whether the caster’s overall design aligns with the actual operating conditions.

A fact that is easy to overlook

Many companies, when replacing casters, simply purchase replacements as long as the mounting dimensions match.

However, if there is a significant difference in the eccentricity design between the new and old products, even when the wheel diameter, mounting plate, and load capacity are identical, the feel of pushing the equipment may still change.

Some may find the vehicle easier to start, while others may experience sluggish steering or even slight shimmying.

This is why, when replacing casters on professional equipment, it’s essential not only to check the dimensions but also to pay close attention to the overall structural design.

Written at the end

Casters are a precision‑engineered mobility system, and every dimension is carefully determined.

The wheel diameter determines the load‑carrying capacity, the wheel material dictates the operating environment, the bearing affects rolling efficiency, and the offset distance determines whether the caster can execute each turn smoothly and stably.

For procurement professionals, understanding eccentricity is not about memorizing a technical term; rather, it helps them gain a more comprehensive grasp of why casters are “easy to use” and enables them to make informed decisions when selecting the right model.

When using casters, do you prioritize ease of pushing and smooth maneuverability, or stability at high speeds? Feel free to leave a comment with the caster‑related expertise you’d like to learn about—we’ll delve deeper in future content.