Bearings are the clock running inside anything that spins

Treat the sections below as a sequence. With bearing failure in consumer products, getting the early decisions right makes the later ones much easier.

What a bearing is doing

A rolling element bearing separates two surfaces with balls or rollers so that friction becomes rolling rather than sliding. The load is carried on very small contact patches, where pressures are enormous and the material is worked repeatedly.

Fatigue eventually causes the hardened surface to flake, which is the classic end of a bearing that was never abused. Manufacturers rate bearings by the load at which a defined proportion survives a defined number of revolutions, which is a statistical statement rather than a promise. Plain bearings and sintered bushes work differently, relying on a film of lubricant between sliding surfaces, and they fail when that film is lost.

Contamination ends most of them

In ordinary products, bearings rarely reach their fatigue life, because dirt or water arrives first. A particle harder than the raceway becomes an indenter under load, and each indentation becomes a stress raiser that spreads.

In the small print, water displaces grease and corrodes the raceway, which is why bearings behind a failed seal deteriorate within months rather than years. Washing machines, garden equipment and anything used outdoors follow this pattern with great consistency. The practical conclusion is that the seal in front of the bearing is the component actually determining service life.

Seals, shields and the trade they make

Shielded bearings have a metal cover with a small clearance, which retains grease and admits fine contamination. Sealed bearings use a contact lip that excludes contamination more effectively and adds friction and heat. Designers choose between them based on speed, temperature and expected environment, and cost pushes towards the cheaper option.

Compared like for like, external seals fitted in the housing protect the bearing seal, and their presence is a strong sign of a design intended to last. A visible drain path that lets water escape before it reaches a bearing is another detail worth looking for in outdoor equipment.

Heat, lubricant and speed

Grease has a service temperature range, and running hot oxidises it until it hardens or separates. Overfilling a bearing with grease causes churning and heat, which is why more lubricant is not better. Higher speeds generate more heat and demand different lubricants, which is why a bearing suited to one application fails quickly in another.

A bearing that becomes audible has usually already been damaged, since noise indicates surface degradation rather than a warning of it.

Catching the first change in sound and acting on it is the only practical form of early intervention available to an owner.

Whether it can be replaced

Bearings are standardised components with published dimension codes, so the part itself is almost always cheap and available. The cost of replacement is entirely about access: whether the assembly comes apart, whether a press is needed, and whether the housing was bonded shut.

Some products are built with the bearing pressed into a moulded housing that is not sold separately, which makes a cheap part into an expensive assembly. Others use a bearing carrier designed for service, sometimes with a published procedure in the service manual. This difference between two otherwise similar products is often invisible at purchase and completely decisive at year seven.

Published coverage skews towards whichever brands were willing to send samples out.

Reading a product for its bearings

Look for a service manual or an exploded diagram, which shows both where the bearings are and how the assembly comes apart. Look for standard bearing codes in the parts list, since a standard code means an open supply chain rather than a proprietary part.

Compared like for like, ask what protects each bearing from water and dust, and treat an unshielded bearing in a wet location as a scheduled failure. Weigh the product, since the mass around a bearing is often a proxy for the size of the bearing chosen. This site does not disassemble products, so teardown coverage and repair technician commentary are where these details are actually documented.

The takeaway

Judge the seal in front of the bearing, because that is what actually decides how long the bearing lasts.

Buy for the failure you can live with, not the feature you will use twice.