Choosing between bi-metallic and metal-polymer composite bearings is not simply a material decision. The wrong choice can lead to excessive friction, premature wear, lubrication problems, or unexpected maintenance requirements—during initial design, replacement selection, or supplier evaluation.

Both bearing types belong to the broader family of self-lubricating or low-lubrication bearings. However, they use different structures, sliding mechanisms, and material systems. Each has advantages depending on the application. This guide compares the two bearing families across load, speed, lubrication, temperature, environment, and lifecycle considerations, and outlines a practical selection framework for OEM buyers.

Terminology note: In this article, “composite bearing” refers specifically to metal-polymer composite bearings, while “bi-metallic bearing” refers to metal-based composite structures. In the bearing industry, composite bearings may refer to different material systems; this article focuses specifically on metal-polymer composite bearings. For a broader overview of bearing families, see our Composite Bearing Selection Guide for OEM Buyers. 

1. What Are Bi-Metallic and Metal-Polymer Composite Bearings?

Bi-Metallic Composite Bearings

Bi-metallic bearings use a steel backing with a sintered bronze or bronze alloy sliding layer. Within this family, two common design approaches exist:

• Lubricated bi-metallic bearings — use oil grooves or grease channels, and operate with initial or periodic lubrication. Typical examples include steel-backed bronze bushings for heavy machinery.

• Solid-lubricant enhanced bi-metallic bearings — incorporate graphite plugs or solid lubricant inserts to provide self-lubricating capability under suitable conditions.

Bi-metallic bearings are often selected where structural strength, load capability, and metallic sliding characteristics are important considerations. They may be considered for heavy-duty equipment where load, speed, lubrication, and construction requirements are compatible.

It is important to note that “bi-metallic” describes a bearing construction, not a lubrication method. Some bi-metallic bearings incorporate self-lubricating features, while others are designed to operate with external lubrication.

Metal-Polymer Composite Bearings

Metal-polymer composite bearings typically use a polymer-based sliding layer combined with a metallic support structure. In common PTFE composite designs, the sliding layer is supported by a sintered bronze interlayer and metal backing—but other metal-polymer structures also exist.

The polymer layer contributes to friction reduction and transfer-film formation, while the metallic structure provides mechanical support. Common applications include hydraulic equipment, packaging machinery, textile machinery, and other systems where dry or low-lubrication operation is required. 

2. Bi-Metallic vs Metal-Polymer Composite Bearings: Performance Comparison

The following table summarizes the main performance differences. Final selection depends on the complete operating conditions and validated material data.

Neither structure is universally superior. A bearing that performs well in one application may be unsuitable in another. For a detailed comparison of PTFE composite and bronze bearings, see our PTFE Composite Bearings vs Bronze Bearings selection guide.

MG-800 vs MG-1: Applying Selection Criteria

The following examples show how the selection criteria discussed in this article can be applied to two specific product families: MG-800 (bi-metallic) and MG-1 (metal-polymer composite). These are examples, not one-to-one rules.

Example 1: Heavy-Duty Pivot Application

Operating conditions:

• High load

• Shock loading

• Periodic lubrication available

• Contamination exposure

Selection consideration: MG-800

Reasoning: The bi-metallic structure provides structural strength and load capability, and the application allows for periodic lubrication.

Example 2: Hydraulic Cylinder Application

Operating conditions:

• Reciprocating motion

• Limited lubrication access

• Low friction requirement

Selection consideration: MG-1

Reasoning: The PTFE sliding layer provides low friction and dry-running capability, reducing maintenance dependency.

These examples illustrate how operating conditions drive bearing structure selection. For a broader decision guide, refer to Section 4 below.

3. Selecting Bearings Based on Operating Conditions

A practical selection process should start with the complete operating system—not simply the bearing material. Load, speed, PV, lubrication, temperature, and shaft condition interact to determine the most suitable bearing structure.

Load

High load does not automatically require a bi-metallic bearing. Evaluate static load, dynamic load, and shock loading. Load direction—radial, axial, or combined—also affects bearing selection.

Speed

Sliding speed affects friction, heat generation, and wear rate. Low-speed, high-load applications may suit bi-metallic structures, while applications requiring low friction under suitable speed conditions may favor metal-polymer designs.

PV Conditions

A bearing material should not be selected by load or speed alone. PV conditions determine whether the sliding surface can operate within an acceptable temperature and wear range. Allowable PV depends on the material system, motion type, temperature, lubrication, and other conditions.

Lubrication

The key question is not simply whether lubrication is available, but whether it is continuous, periodic, or impractical. This determines whether a self-lubricating bearing or a lubrication-assisted design is more appropriate.

Temperature

Continuous and peak temperatures affect material stability, clearance, and wear. Metal-based structures may be considered for higher-temperature applications depending on lubrication condition and material combination. For a detailed discussion of dry-running and lubricated bearing behavior, see our Dry-Running Bearings vs Lubricated Bearings guide.

Shaft Condition and Installation

Shaft material, hardness, surface finish, and alignment directly affect sliding performance. Installation accuracy—including housing deformation and clearance—also influences bearing life. For failure diagnosis, see our PTFE Composite Bearing Failure Diagnosis.

Lifecycle Cost

Evaluate initial cost and lifecycle cost separately. Maintenance frequency, downtime risk, and replacement intervals often outweigh the initial purchase price.

4. Industry Application Considerations

The following examples illustrate how different industries typically evaluate bearing structure selection. These are starting points rather than one-to-one rules. Final selection should be based on the complete operating conditions and validated material data.

Construction Machinery

Applications with high impact loading, contamination exposure, and structural strength requirements may require bearing structures with higher mechanical robustness. OEMs often focus on replacement interval, grease accessibility, and shock loading frequency. Bi-metallic bearings are often considered where load capability and contamination tolerance are priorities.

Hydraulic Equipment

Hydraulic cylinders and reciprocating mechanisms often require low friction, dry-running capability, and wear resistance. OEMs typically evaluate startup friction, stick-slip risk, and cylinder surface condition. Metal-polymer composite bearings with PTFE sliding layers are commonly considered for these applications.

Agricultural Machinery

Agricultural equipment may face shock loading, dust and mud contamination, and limited maintenance access. OEMs often prioritize durability under contamination and ease of replacement. Depending on the specific application, both bi-metallic and solid-lubricant enhanced bearings may be considered.

Automation and Packaging Equipment

Automation and packaging systems often require low friction, frequent movement, compact design, and reduced lubrication. OEMs typically focus on repeatability, noise level, and maintenance-free operation. Metal-polymer composite bearings are commonly selected for these conditions.

Mining and Heavy Industry

Heavy-duty equipment operating under high loads and contamination may require structures that provide high load capability and structural strength. OEMs often evaluate load capacity, wear life, and lubrication availability. Bi-metallic or solid-lubricant enhanced designs may be considered depending on lubrication availability.

For a broader framework covering material selection, cost, and supplier evaluation, see our Composite Bearing Selection Guide for OEM Buyers.

5. What OEM Buyers Should Confirm Before RFQ Approval

Before approving a bearing selection for RFQ, OEM buyers should confirm the following:

Before RFQ

• Drawing and dimensions

• Operating conditions (load, speed, motion, temperature)

• Shaft specification (material, hardness, surface finish)

• Material requirements and lubrication condition

During Sample Approval

• Dimensional inspection record

• Material certificate

• Test requirement and validation results

Before Mass Production

• Batch consistency records

• Traceability method

• Change control procedure

For a deeper look at how manufacturing, customization, and quality control are managed, see our OEM Composite Bearings: Customization, Materials, Manufacturing & Quality Control guide. For buyers sourcing from China, supplier verification is an additional critical step—see our Importing Composite Bearings from China: What Industrial Buyers Should Verify guide.

6. FAQ: Bi-Metallic vs Metal-Polymer Composite Bearings

Are bi-metallic bearings always better for high loads?

No. Load capability depends on bearing design, material combination, lubrication, and operating conditions. Some metal-polymer composite bearings also provide high load capacity in suitable designs.

Can metal-polymer bearings replace bronze bearings?

It depends on load, speed, temperature, shaft condition, and lubrication requirements. Metal-polymer bearings are often considered when dry running or reduced maintenance is a priority, while bronze bearings may remain suitable for other conditions.

Are metal-polymer bearings maintenance-free?

They can reduce lubrication requirements, but service life still depends on PV conditions, shaft condition, installation quality, and operating environment.

How should OEM buyers choose between MG-800 and MG-1?

Start from operating conditions rather than catalog selection. MG-800 is often considered for high load and impact conditions where lubrication is available. MG-1 is often considered for dry running, low friction, and reduced maintenance requirements.

What is the difference between bi-metallic and composite bearings?

“Composite bearing” is a broad term that can refer to several material systems. In this article, composite bearing refers specifically to metal-polymer composite bearings. Bi-metallic bearings are a separate construction family that uses a metal-based sliding layer. The two are not mutually exclusive categories; they describe different aspects of bearing construction.

What information should OEM buyers provide when requesting a composite bearing quotation?

Useful information includes the bearing drawing or dimensions, load and speed conditions, motion type, lubrication condition, shaft specification, operating temperature, and annual demand. These details allow the supplier to review the required bearing structure and provide a quotation or sample proposal. See Section 5 above for a complete RFQ checklist.

What is the most important factor in bearing selection?

No single factor determines the right bearing. Load, speed, PV, lubrication, temperature, environment, and shaft condition should all be evaluated together.

Conclusion: Match Bearing Structure to Application

Bi-metallic and metal-polymer composite bearings are not competing products—they solve different engineering problems. Selecting the right structure requires understanding the complete operating system, including motion, load, speed, lubrication, temperature, environment, and shaft condition.

The key selection principle: match the bearing structure to the application, not the catalog. This approach helps OEM buyers reduce selection risk during new design projects and replacement sourcing.

For OEM buyers, this usually means evaluating the operating conditions first, then selecting the bearing structure and material system.

If you are evaluating either bearing type for an OEM application, you can send us your drawing, load and speed conditions, shaft specification, current bearing issue, or annual demand for technical discussion. Our engineering team can review the required bearing type, confirm suitable material and structure, discuss manufacturing and inspection considerations, and provide a quotation or sample proposal based on the approved requirements.