Bicycle bearings are small components, but they have a major influence on how smoothly, accurately and reliably a bicycle operates. Wheel hubs, bottom brackets, headsets, pedals, derailleur pulleys, suspension pivots and e-bike motors all rely on bearings, but the operating conditions at each position are very different.

For bicycle manufacturers, component brands, distributors and aftermarket suppliers, choosing the correct bearing involves more than matching the inner diameter, outer diameter and width. Load direction, sealing, contact angle, lubrication, precision, installation fit and service environment can all affect bearing life and performance.

This guide explains the main bicycle bearing applications, common bearing types, sizing basics and the key factors to consider when selecting bearings for standard, replacement and OEM bicycle projects.

Where Are Bearings Used on a Bicycle?

A modern road bike, mountain bike or e-bike may contain several different bearing systems. Common locations include:

• Wheel hubs
• Bottom brackets
• Headsets
• Pedals
• Rear derailleur pulley wheels
• Suspension pivots
• E-bike motors and drive systems

Each location creates a different combination of radial load, axial load, speed, contamination, vibration and installation constraints. Selecting the bearing according to the application is therefore more reliable than choosing by size alone.

1. Bicycle Hub Bearings

Hub bearings are installed inside the front and rear wheel hubs and allow the wheel to rotate around the axle while supporting the bicycle and rider. They primarily carry radial loads, but cornering, braking, hub design and installation can also introduce axial loads.

Sealed cartridge ball bearings are widely used in modern bicycle hubs because they are compact, replaceable and well protected from road contamination. For higher-performance hubs, manufacturers may also use angular-contact arrangements, precision steel bearings or hybrid ceramic bearings depending on the design target.

Important hub-bearing selection factors include:

• Low rotational friction
• Radial and axial load capacity
• Stable internal clearance
• Effective sealing against water and dust
• Corrosion resistance
• Consistent dimensional accuracy
• Suitable grease and long lubrication life

For OEM projects, the hub body, axle diameter, shoulder geometry and press fit should be checked together with the bearing dimensions. Excessive interference can increase internal preload and friction, while insufficient fit can allow movement in the housing.

2. Bottom Bracket Bearings

Bottom bracket bearings support the crank spindle and transfer pedaling forces between the crankset and bicycle frame. Their rotational speed is relatively low, but the loads can be substantial and may include both radial and axial components.

Different bottom bracket systems use different bearing sizes and arrangements, including threaded and press-fit designs. Bearing life depends not only on the bearing itself but also on spindle alignment, housing tolerances, contamination protection and installation method.

Key factors to confirm include bearing dimensions, load capacity, seal design, grease selection, corrosion protection, raceway accuracy and installation fit. When an existing model number is unavailable, a drawing or physical sample can help confirm the correct construction.

3. Bicycle Headset Bearings

Headset bearings are located between the bicycle frame and fork and allow smooth steering. Unlike hub bearings, they normally rotate only through a limited angle, but they must withstand repeated radial loads, axial loads and impacts transmitted through the front wheel and fork.

Angular-contact cartridge bearings are common in modern headsets. Their contact angle and chamfer geometry are important because two bearings with similar outside dimensions may not be interchangeable if the angular geometry is different.

For headset bearings, confirm the inner diameter, outer diameter, height, contact angle, chamfer, seal type and installation direction. Correct preload is also important for smooth steering without play.

4. Bicycle Pedal Bearings

Pedal bearings allow the pedal body to rotate around the spindle. Because the available installation space is limited, pedals often use miniature deep-groove ball bearings, needle roller bearings, bushings or combinations of several support elements.

Pedal bearings should provide compact dimensions, low friction, good radial load capacity, stable rotation and effective sealing. Repeated pedaling loads and exposure to water and dirt make seal design and lubrication especially important.

For OEM supply, the safest selection method is to work from the component drawing, existing sample or confirmed bearing dimensions together with the spindle and housing design.

5. Derailleur Pulley Bearings

Small precision bearings are used inside rear derailleur pulley wheels to support the pulley and help the chain move smoothly through the drivetrain. Because the bearing is very small, contamination and seal friction can have a noticeable influence on operation.

Typical requirements include low starting torque, low rotational resistance, compact dimensions, effective seals and stable grease performance. Stainless-steel or hybrid ceramic options can also be considered when the application requires additional corrosion resistance or specialized performance characteristics.

6. Suspension Pivot Bearings

Full-suspension mountain bikes use bearings at multiple pivot points between the frame, rear triangle and suspension linkage. These bearings operate very differently from hub bearings: instead of continuous rotation, they typically oscillate through a relatively small angle while carrying high loads.

Suspension pivot bearings may be exposed to shock loads, mud, water, vibration and repeated low-angle movement. Static load capacity, seal performance, corrosion resistance, lubrication, internal clearance and housing fit are therefore more important than maximum speed in many pivot applications.

7. E-Bike Motor Bearings

Electric bicycles introduce additional bearing requirements because the drive system can operate continuously at higher speed and temperature than conventional bicycle components. Bearings may be used in hub motors, mid-drive motors, reduction gears and auxiliary transmission parts.

When selecting e-bike motor bearings, consider motor speed, radial and axial loads, operating temperature, noise, vibration, seal friction and expected lubrication life. Precision deep-groove ball bearings are commonly used, while stainless-steel or hybrid ceramic solutions may be evaluated for specialized environments.

Common Types of Bicycle Bearings

Deep Groove Ball Bearings

Deep groove ball bearings are among the most widely used bearing types in bicycles. They are compact, economical and capable of carrying primarily radial loads together with moderate axial loads. Common applications include hubs, pedals, pulley systems and e-bike motors.

Angular Contact Bearings

Angular contact bearings are designed to carry combined radial and axial loads. They are especially useful where preload, axial positioning and steering or crank alignment are important, such as in headset and some bottom bracket or hub systems.

Miniature Ball Bearings

Miniature bearings are used where installation space is limited, including pedals, derailleur pulleys and other compact rotating components. In these small bearings, raceway accuracy, seal friction and grease quantity can strongly affect rotational performance.

Needle Roller Bearings

Needle roller bearings provide high radial load capacity in a small radial cross-section. They can be used in some pedals and specialized bicycle mechanisms where compact installation space is required.

Steel vs. Ceramic Bicycle Bearings

There is no single bearing material that is automatically best for every bicycle application. The correct choice depends on load, speed, sealing, lubrication, contamination, cost target and expected service life.

Steel Bearings

High-quality bearing steel remains a practical solution for most bicycle applications because it provides strong load capacity, good fatigue resistance, mature manufacturing technology and competitive cost. A correctly manufactured and lubricated steel bearing can deliver excellent service life in hubs, bottom brackets, pedals and many other bicycle components.

Hybrid Ceramic Bearings

Hybrid ceramic bearings generally use ceramic balls together with steel inner and outer rings. Depending on the design and operating conditions, they may be selected for lower ball mass, high hardness, electrical insulation characteristics or specialized high-speed performance. However, ceramic balls alone do not guarantee lower friction or longer life; raceway quality, sealing, lubrication and installation remain critical.

Sealed vs. Shielded Bicycle Bearings

Bicycle bearings frequently operate in environments containing dust, water and road contamination, so the sealing system is a major selection factor.

2RS Rubber Seals

2RS normally indicates rubber seals on both sides of the bearing. Rubber seals generally provide stronger protection against water and contamination and are widely used in exposed bicycle applications such as hubs, bottom brackets and suspension pivots. The trade-off is slightly higher seal friction.

ZZ Metal Shields

ZZ bearings use metal shields on both sides. They can provide lower contact friction but usually offer less protection against water than contact rubber seals. They are more suitable for relatively clean or enclosed operating environments.

How to Measure a Bicycle Bearing

When identifying a replacement or sourcing an OEM bicycle bearing, three basic dimensions should normally be confirmed:

1. Inner Diameter (ID) – the diameter of the hole through the center of the bearing.
2. Outer Diameter (OD) – the outside diameter of the bearing.
3. Width (W) – the total thickness of the bearing.

Example: 8 × 22 × 7 mm means an 8 mm inner diameter, 22 mm outer diameter and 7 mm width.

Dimensions alone are not always sufficient. Buyers should also confirm the bearing type, seal or shield, internal clearance, material, contact angle when applicable, flange or special geometry, and the exact application position.

What Information Should Buyers Provide?

For OEM, replacement and distribution projects, providing complete information helps reduce identification errors and speeds up technical evaluation. We recommend providing:

4. Bearing model number
5. Inner diameter, outer diameter and width
6. Seal or shield requirement
7. Material requirement
8. Application position
9. Operating load or performance requirement
10. Speed requirement where relevant
11. Drawing or physical sample
12. Estimated order quantity
13. Annual demand

For non-standard bicycle bearings, a drawing or physical sample is often the fastest way to confirm dimensions, geometry, seals and special requirements.

Choosing Bicycle Bearings for OEM Applications

Load

Determine whether the bearing carries mainly radial load, axial load or combined load. A bearing that works well in a hub may not be suitable for a headset or suspension pivot.

Speed

Hub and motor bearings may operate at higher speed than headset or suspension bearings. Speed affects lubrication, heat generation and seal selection.

Environment

Mountain bikes, commuter bicycles and e-bikes may operate in rain, dust, mud or high humidity. Seal design and corrosion protection should match the service environment.

Precision and Friction

Hub, motor and drivetrain applications may require tighter rotational accuracy and low torque. Precision should be selected according to the actual product requirement rather than specified at an unnecessarily high level.

Service Life

A low purchase price does not always result in the lowest total cost if premature bearing failure leads to warranty claims, service work or component replacement.

Custom Bicycle Bearing Solutions

Standard catalog bearings can satisfy many bicycle applications, but some bicycle components require customized bearing solutions. Depending on the project, customization can include:

• Special dimensions
• Non-standard inner or outer rings
• Flanged designs
• Special seals
• Different grease specifications
• Stainless-steel materials
• Hybrid ceramic balls
• Custom internal clearance
• Application-specific precision requirements
• Laser marking
• Private labeling
• Custom packaging

For a new bicycle component, involving the bearing supplier during the design stage can help prevent later problems with housing fit, sealing, preload and service life.

The RMO OEM Advantage: We don’t just supply standard bearing sizes. Our engineering team can work with bicycle manufacturers during the design and sampling stage to evaluate housing fit, sealing, preload and lubrication requirements before mass production. From application-specific grease and seal configurations to stainless-steel and hybrid ceramic options, RMO supports sample development and technical evaluation to help reduce design risk and keep OEM projects moving forward.

Frequently Asked Questions

What bearings are commonly used in bicycle hubs?

Sealed deep-groove ball bearings are widely used in modern cartridge-style hubs, while some hub designs use angular-contact arrangements or other constructions according to the load and adjustment system.

Are ceramic bearings better for bicycles?

Ceramic or hybrid ceramic bearings can provide benefits in certain applications, but the result depends on the complete bearing design, raceway quality, lubrication, sealing and operating conditions. They should be selected for a specific performance requirement rather than treated as automatically superior in every application.

What does 2RS mean on a bicycle bearing?

2RS normally means that the bearing has rubber seals on both sides. This sealing arrangement is commonly used where stronger protection from water and contamination is needed.

Can bicycle bearings be customized?

Yes. Depending on the application and order requirements, dimensions, materials, seals, grease, clearance, precision, marking and packaging can be customized.

How do I identify a bicycle bearing?

Start with the model number printed on the bearing. If the marking is unavailable, measure the inner diameter, outer diameter and width, then confirm the application, seal type and any special geometry. A clear photo, drawing or sample can further improve identification accuracy.

Don’t Let the Wrong Bearing Derail Your Bicycle Project.

Whether you are developing a high-torque e-bike motor, a lightweight precision hub or a custom drivetrain component, bearing selection can affect friction, sealing, service life and overall product reliability.

Send RMO Bearings your bearing model, dimensions, drawing or application requirements. Our technical team can review the project and recommend a suitable bearing configuration before mass production.

Qualified OEM projects can also request sample testing before bulk production.

Request a Bicycle Bearing Technical Review & Sample