Your complete guide to bearings
Words by Charlotte Head
Bikes are made up of many components requiring regular servicing to keep them running smoothly. None are more crucial than bearings. Almost any part of your bike that can move operates on bearings and, if not cared for properly, can seriously hinder your bike’s performance. Let’s look at what a bearing actually is, the different types that exist, and how you can best care for them.
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What is a bearing?
A bearing is defined as “a part of a machine that allows one part to rotate or move in contact with another part with as little friction as possible.” (Oxford Language) In short, they facilitate movement when two materials are in contact. Though not something we may always consider, there are many moving parts on a bicycle. The headset allows your handlebars and front wheel to move, the bottom bracket allows your cranks to turn for you to pedal, and the wheel bearings allow them to spin freely.
There are two common types of bearings: loose bearings and sealed bearings. Loose bearings are what they say on the tin - they comprise loose ball bearings, which sit inside either a metal cage or flush against a metal race. They are then packed with grease to reduce friction, helping them move more easily and reduce wear. Loose bearings were the standard in traditional bike building, and they are still used today.
Sealed bearings are an evolution of the loose bearing design. Rather than the bearings making direct contact with a component, sealed bearings operate within their own unit, confining the wear inside the bearing itself. The ball bearings are surrounded by an inner and outer race, and an inner and outer seal.
As bearings have developed, new materials have been introduced, focusing on performance and longevity. As with traditional loose bearings, stainless steel ball bearings are still the standard today. This is the default material unless otherwise stated.
In more recent years, ceramic bearings have been introduced into pro-cycling and have trickled down to general retail. There are two main types: hybrid ceramic and full ceramic. The former houses ceramic ball bearings in a steel cage, and the latter, both parts are ceramic. The theory is that ceramic bearings can be made almost perfectly spherical, reducing friction, requiring less maintenance, and are harder so they last longer. There is much debate about whether the steel cage in a hybrid bearing severely impacts this claim and whether ceramic bearings can produce results worthy of their price tags. The main point to focus on is that there are different materials to suit different needs, and it is best to research or ask for advice if you are thinking of upgrading your sealed bearings. For more information see road.cc’s article, should you buy ceramic bearings?
Material aside, sealed bearings offer significant benefits compared to their traditional counterparts.
With use, bearings will eventually begin to feel rough. This is either due to the ball bearings themselves becoming misshapen or because the surface they make contact with has become ‘pitted’. ‘Pitting’ is where the ball bearing has worn away or left indentations on the surface, and the contact point is no longer smooth. In loose ball bearings, this surface is typically a direct part of the component, i.e. hub internals, a bottom bracket spindle, headset cup etc. As stated above, sealed bearings contain this within the bearing itself.
When loose bearing surfaces become pitted, changing the bearings will have little impact on the overall performance and is unlikely to help the component run much smoother. With sealed bearings, replacing the whole bearing includes both bearing and surface alike, leaving that part running like new. Furthermore, the seal helps protect the ball bearings from the elements and keeps the grease in for longer.
It is key to note that components will contain either loose or sealed bearings when new and will not be cross-compatible with the other. Knowing which type of bearing you are looking for can help you make an informed decision when changing or upgrading components, particularly on larger ticket items such as wheels.
Though designed to be long lasting and more durable, Sealed bearings are not eternal and still need servicing and regular check-ups. If you leave it until the bearings barely spin anymore or have so much play (movement) that the components rock side to side, the damage can extend beyond the bearing itself. Worn out hub bearings can damage the wheel’s axle, bottom bracket bearings can damage the spindle, and headset bearings can damage the steerer tube itself.
When left unserviced, worn-out sealed bearings can be difficult to remove, as rust often gathers over time, especially if the bike has been left in standing water or dirt after a ride. This can lead to issues during the service, and a headache for you, your mechanic and your wallet.
To keep your bearings healthy and replace when needed, look out for the following signs:
- Clicking (sound or feeling)
- Play (movement)
- Rumbling sound
If you notice any of these around your bearings, get your bike in for a check-up at your local bike shop - the sooner, the better!
The do’s + don’ts
|Cover areas such as the headset when using a turbo trainer to protect bearings from sweat (salt + steel = rust).||Clean the area with a jet wash. This will strip out the grease.|
|Get regular services to help extend bearing life.||Leave your bike in standing water or dirt after a ride, leading to rust.|
|Investigate as soon as you feel play (movement) in the bearing area, to protect other components.||Think you need to upgrade to ceramic bearings for the sake of it.|
|Look for sealed bearings when upgrading components.|
Overall, the technology of bearings has come on in leaps and bounds in recent years, with sealed bearings offering a cost-effective alternative to traditional loose bearings. As the bearings can be replaced when worn, rather than the whole component, they are a great contribution to the “repair don’t replace” movement and are designed to keep working smoother for longer. Looking out for sealed bearing parts when making upgrades can be a savvy move, in the long run, reducing the number of disposable components and breathing more life into your bike as a whole.