Bicycle bearings: everything you need to know

Nov 25, 2023

The bits that keep your bike rolling

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By Thomas McDaniel, Jack Luke

Published: April 3, 2018 at 5:00 pm

Bearings often-overlooked components that actually bring life to your bicycle. You can't steer, roll, pedal or have a functioning drivetrain without bearings.

Bearings are found in your hubs, bottom bracket, headset, suspension pivots, pedals, shifters… the list goes on – basically, anything that moves on your bike will have some kind of bearing in it.

In this guide we’ll go over the different types of bearings commonly used on a bike, how to measure the bearings on your bike, what makes one bearing better than another and how to maintain bearings.

Loose ball, caged ball, bushings, needle, and cartridge are the main styles of bearing founds in cycling frames and components. Here, we explain how each type of bearings differs from another.

A bushing (also known as a bush, or sleeve bearing) is a type of plain bearing used in shock mounts, cheaper pulley wheels and shifters.

A bushing is the simplest type of bearing and is just a sleeve that sits between two surfaces to reduce friction.

A loose ball bearing system comprises:

The contact surfaces of the cup and cone are machined to a smooth finish that matches the profile of the bearings, and this is what they run on.

Loose ball bearings are commonly used everywhere on entry-level bikes, including hubs, bottom brackets and headsets.

At the higher-end, most brands have moved away from loose ball bearings, though Shimano and Campagnolo are notable holdouts, with both using very high-quality cup and cone bearings in most of their hubs. Shimano also uses loose bearings in its pedals.

Although they’re the oldest, in many ways they can be superior. They are angular contact (more on this later), relatively easy to maintain and can perform exceptionally if well-adjusted.

Loose ball bearings are sometimes held within a retainer, which is also known as a cage (hence the named ‘caged bearings’). This is usually made from pressed steel and holds the loose ball bearings apart from one another.

Though often associated with the low-end, caged bearings aren't universally bad – Campagnolo's CULT bearings, which exhibit excellent performance characteristics, are caged bearings. Cane Creek's Hellbender Neo bearings are another interesting take on the concept.

Cartridge bearings are the most common type of bearing used on anything but the very cheapest bikes.

These are a one-piece unit that is, usually, pressed into a bearing bore.

A typical radial cartridge bearing is made up of:

These bearings cannot be adjusted or fully disassembled.

Cartridge systems require precision to function well but, as manufacturing technology has moved on, they have become increasingly used as a result of ever-increasing tolerances in hub, frame, and component bores.

Needle bearings, which are also known as roller bearings, are relatively uncommon in the cycling world.

The exception is pedals and very occasionally in headsets, but even then they’ve lost a lot of ground to newer and cheaper tech.

In a needle bearing, instead of ball bearings, the bearings themselves are cylindrical.

They can create incredibly smooth rolling and stable platforms, especially under high loads, but in the cycling industry there's a tendency to shy away from them due to the expense and complication of creating good mating surfaces.

When not mated properly, they tend to fatigue quickly. Needle bearings often get replaced by multiple rows of cartridge bearings to achieve the same effect.

Loose ball-bearing sizes are determined by the diameter of the ball bearing itself. This is usually expressed as a fraction of an inch: 3/16in (4.7625 mm).

The exact size of bearing required will differ between individual components.

It is usually possible to also replace the cone in a loose ball bearing setup, but the cups (particularly in hubs) are less commonly replaceable.

A cartridge bearing's size is determined by its inside diameter (ID), outside diameter (OD) and width.

The measurements take the form of ‘15x24x5mm’ or similar.

They often have a corresponding universal identifier, which in the case of the aforementioned bearing, would be 6802, for instance.

With calipers, you can measure a cartridge, enabling you to find a replacement quite easily.

Headsets pose a unique characteristic in that they have angled races. Their sizing might read more like ‘46.9 x 7 x 45°’ to identify the OD, width and angular measurements of the bearing race, respectively.

In regards to performance, generally speaking, the bigger the ball inside the bearing, the better, as increasing diameter has an exponential factor for increasing contact. More contact means more even distribution of forces, and results in better rolling performance and durability.

Several major wheel manufacturers have pushed towards larger bearings in recent years and there are ever-increasing hub dimensions to show.

Two types of cartridge bearings are commonly used in bikes: radial and angular contact.

Radial bearings are the most common as they are cheaper. They attempt to carry the load in a truly radial direction, which is vertical in terms of hubs, cranks, suspension pivots or derailleur pulleys.

Subsequently, they sacrifice a small amount of performance because forces within these moving parts usually have a non-radial vector associated. As a result, they have to compensate with decreased tolerances.

In short, there's less precision associated with radial cartridge systems. As such, they don't have any directional application — there is no inside or outside.

As a benefit, because they are slightly less tolerance-dependent, they can be used in applications that aren't quite as expensive.

Conversely, angular contact bearings require tight tolerances because they are directional. There is an inside and outside component, and they can be compared to the old-style cup-and-cone systems in terms of design.

They complement the radial and side-force loads exerted with the rotating components of a bike, but require extreme tolerances in mating bores to accomplish a precise fit and rolling performance.

For the most part, angular contact is the most appropriate application for hubs, cranks and suspension. However, many hubs and frames don't posses the mating bore to complement the precision of the angular cartridge.

This precision is where brands such as Industry 9, Chris King, White Industries, Phil Wood and Alchemy Wheel Works get their reputation.

You will commonly see bearings referred to as ‘ABEC’ followed by a number (Eg, ABEC 1, 3, 5, 7, and 9).

In brief, the higher the number, the higher quality of the bearing. It serves as a rough ‘good, better, best sort’ of metric, but Chuck Panaccione from Enduro Bearings says this standard is lacking.

What the ABEC standard qualifies is bore diameter (an acceptable variation of the size of the inner bearing hole), parallelism (width variation), and the radial raceway run-out (variations in the groove in which the balls sit).

But Panaccione made it clear that the ABEC system forgoes load handling, ball precision or Rockwell Hardness (material hardness).

The folks at Enduro Bearings argue that, for bicycles, the materials are far more important than ABEC ratings and that for most applications, ABEC 3 and 5 are appropriate for all things bicycle.

As for the 7 and 9 ratings, that level of precision is for equipment that sees rotations in the thousands or hundreds of thousands per minute — a tad overkill for cycling.

Cartridge bearings are usually sealed with two rubber seals on either face of the bearing.

They may sound like a dry and boring topic (pun intended), but they have a big bearing (eyyy) on the overall performance of a bearing.

There are three major considerations regarding seals — friction, protection and serviceability.

Friction is a major point of contention for cartridge bearings, and while less is better, a little friction can be an indication of protection.

The job of the seal is just that – to keep grease in and contaminants out.

But once you have contamination, can you clean and service your cartridge without damaging the seal?

For most quality bearings, including every bearing Enduro Bearings makes, Panaccione assures "with a small blade and a careful hand, seals can be removed from the inside race for servicing".

Bearings are made from a huge range of materials. Some examples include chromium steel, 440C stainless steel, XD15 super nitrogen stainless, and silicone nitride (ceramic bearings).

Generally speaking, the harder the material the better, but there is a point of diminishing returns.

Ultimately, too hard means the balls can become brittle, which is no better than too soft.

Balancing the application of the bearing (hub, crank, suspension pivot, etc), how much service you’re willing to put in, and picking a budget are all consideration brands have to make when speccing bearings.

Like any moving part on your bike, bearings require servicing. Maintenance intervals will be longer on higher-quality bearings, but no one bearing is truly ‘fit and forget’.

Proper installation plays a big part in bearing longevity too.

It may seem simple enough, but misalignment from improper installs are a big cause of premature wear.

Also, if you’re working with angular contact bearings, the seals are different colours for a reason – Black seals are meant to face the centerline, while red should face outwards.

Proper bearing maintenance ends with proper lubrication, which could be anything from sticky waterproof grease to thin frictionless lube.

Depending on the application, the type of bearing system used, how often maintenance is done, and the type of environmental exposure the system experiences will dictate the best lubricant.

For more info, check out our in-depth guide on how to service bearings.

Deputy editor

Jack Luke is the deputy editor at BikeRadar and has been fettling with bikes for his whole life. Always in search of the hippest new niche in cycling, Jack is a self-confessed gravel dork, fixie-botherer, tandem-evangelist and hill climb try hard. Jack thinks nothing of bikepacking after work to sleep in a ditch or taking on a daft challenge for the BikeRadar YouTube channel. He is also a regular contributor to the BikeRadar podcast. With a near encyclopaedic knowledge of cycling tech, ranging from the most esoteric retro niche to the most cutting-edge modern kit, Jack takes pride in his ability to seek out stories that would otherwise go unreported. He is also particularly fond of tan-wall tyres, dynamo lights, cup and cone bearings, and skids. Jack has been writing about and testing bikes for more than six years now, has a background working in bike shops for years before that, and is regularly found riding a mix of weird and wonderful machines. Jack can also often be seen zooming about with his partner aboard their beloved tandem.

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