During the use of casters, one type of failure is particularly obvious: a previously intact wheel surface suddenly develops a chipped corner, with notches appearing along the edge; in severe cases, small fragments of material may even fall off continuously.

Seeing this situation on site, it’s easy to conclude: “The wheel material is too brittle.”

However, chipping or spalling on the wheel tread of casters does not necessarily stem solely from the material itself. Foreign objects on the track, lateral impacts, localized stresses, wheel tread conditions, and operating modes of the equipment can all play a role.

Especially with industrial casters made of polyurethane, nylon, and other materials, to determine why “a piece is missing,” the first step is to clarify exactly how that piece came off.

I. First, determine whether it’s “ground off” or “chipped off.”

Normal wear is typically a relatively slow process.

As operating time increases, the wheel tread gradually wears down and the contact area shifts, but the overall profile typically does not suddenly lose a large section.

Chipping, however, is different.

It often manifests as a distinct notch at the fracture site, with the fracture surface relatively concentrated, while the surrounding wheel tread may remain largely intact.

Therefore, the first step during inspection is not to assess how long the wheel has been in use, but rather to examine the nature of the damage.

If only a single location exhibits sudden wear, local abnormal loading should be given priority over simply attributing it to normal attrition.

II. Sharp foreign objects may be the most direct causative factor.

Industrial workshop floors are not always clean and level.

The metalworking area may contain iron filings, scrap metal, screws, and other hard debris.

When a fully loaded piece of equipment rolls over these foreign objects, the wheel–track contact area experiences highly concentrated stresses.

Some foreign objects may even initially cause cuts on the wheel surface.

Subsequently, as the casters continue to roll, this small notch may become the site where the damage propagates, ultimately resulting in a chipped edge visible to the naked eye.

So, once you notice a chunk has fallen off, don’t just inspect the wheel.

Walking through the equipment’s daily route is often just as important.

3. A side-on collision is more alarming than rolling straight into it.

When the caster is operating normally, its wheel surface primarily makes rolling contact with the ground.

However, on-site operations are not always so ideal.

When the cart approaches equipment, shelving, tracks, or wall corners, the wheel sides may directly strike hard objects; when navigating narrow spaces, the wheel flanges may also experience scraping or impact.

This mode of operation is entirely different from normal scrolling.

In particular, after the wheel tread edge is repeatedly subjected to lateral impacts, localized notches may first develop and then gradually propagate.

Therefore, if spalling consistently occurs at the wheel tread edge, it is advisable to thoroughly investigate whether the equipment is subject to frequent lateral impacts.

IV. Why does only one wheel on the same vehicle have a spall?

This phenomenon is highly valuable for troubleshooting.

If four casters are of similar specifications and have been in use for roughly the same amount of time, yet only the one at a fixed location keeps failing, don’t rush to suspect the entire batch of materials.

You can observe whether the location of this caster is more prone to colliding with obstacles, whether it frequently runs along the edge of the travel path during equipment turns, and whether that position is subjected to different real-world operating conditions.

Sometimes, the real cause lies not in the caster factory, but in a particular motion that the equipment repeats day after day.

5. Changes in the material’s condition may also increase the risk of spalling.

After prolonged exposure to a specific environment, the material of the caster wheel’s tread may undergo changes.

For example, when exposed over the long term to temperature, chemical media, light, or other environmental factors, a material’s properties may differ from their initial state.

At this point, encountering a sharp foreign object or a strong localized impact will more readily reveal the underlying issue.

This is also why failure analysis cannot focus solely on the final event.

Seeing a chunk of the wheel surface broken off does not mean that all the damage was caused by that single impact.

The final blow sometimes merely brings pre-existing damage fully to light.

6. If a small piece is chipped off, can it still be used?

It should be determined based on the extent of the damage and the intended use of the equipment, rather than simply judging whether it can still rotate.

If only minor surface notches are detected, first halt the operating conditions that could exacerbate the damage and monitor the condition of the defect.

If the damage has significantly compromised the wheel tread’s integrity, or if it exhibits progressive propagation or cracks extending inward, it should be addressed promptly.

For casters subjected to heavy loads, frequent operation, or serving critical equipment, it is even less advisable to wait until the tread surface has sustained extensive damage before replacing them.

As the gap widens, each rotation of the wheel repeatedly passes through this discontinuous region, causing the operating state to change accordingly.

VII. Reducing Chipping: On-Site Management Is Equally Important

To reduce chipping on casters, you can’t rely solely on “switching to better materials.”

Keep the transport channels clean and promptly remove metal chips and hard foreign objects.

Improve noticeably sharp steps and damaged flooring;

Avoid having the cart’s wheels directly impact equipment foundations or racking.

Inspect the wheel tread for cuts promptly, rather than waiting for them to worsen.

These seemingly simple measures are often crucial for the long-term operation of casters.

Written at the end

The casters have chipped surfaces, which might seem like a typical case of “a defective product,” but the real cause could be hidden in the equipment’s daily travel routes.

Chipping is the outcome; identifying the initial site of damage is the key to failure analysis.

Next time you notice a caster has suddenly chipped, don’t rush to ask, “Why is this wheel so brittle?” Instead, examine the location and shape of the chip, then inspect the floor and the equipment’s path of movement.

Sometimes, an inconspicuous metal fragment—or a single lateral impact that occurs every day—is the true root of the problem.