Friction materials used in clutches and brakes are critical components in mechanical systems, providing controlled transmission and dissipation of energy through friction. The performance, safety and durability of these systems depend heavily on the properties of the materials used.
This page outlines the desirable properties of friction materials and provides typical values for coefficient of friction, temperature limits and contact pressures for common material combinations.
Safety Note: Asbestos-based friction materials are hazardous to health and are no longer acceptable for use in modern brake and clutch systems.
Friction coefficients vary depending on whether the contact surfaces are lubricated (wet) or unlubricated (dry). Materials such as carbon-graphite and Kevlar-based composites offer improved performance at higher temperatures and pressures compared to traditional materials.
Note: Brake materials from asbestos are not safe and are no longer acceptable for use in
brakes and clutches
Note: These properties are very general in nature and should not be used for detail design. Suppliers
information should be used for important work. Asbestos should not be used for new or replacement
equipment.
| Material Combination | Coefficient of Friction | Temp.(max) | Pressure (Max) | |
| Wet | Dry | Deg.C | MPa | |
| Cast Iron/Cast Iron | 0,05 | 0,15-0,20 | 300 | 0,8 |
| Cast Iron/Steel | 0,06 | 0,15-0,20 | 300 | 0,8-1,3 |
| Hard Steel/Hard Steel | 0,05 | 0,15-0,20 | 300 | 0,7 |
| Wood/Cast Iron-steel | 0,16 | 0,2-0,35 | 150 | 0,6 |
| Leather/Cast Iron-steel | 0,12-0,15 | 0,3-0,5 | 100 | 0,25 |
| Cork/Cast Iron- Steel | 0,15-0,25 | 0,3-0,5 | 100 | 0,1 |
| Felt/Cast Iron- Steel | 0,18 | 0,22 | 140 | 0,06 |
| Woven Asbestos/Cast Iron- Steel | 0,1-0,2 | 0,3-0,6 | 250 | 0,7 |
| Moulded Asbestos/Cast Iron- Steel | 0,08-0,12 | 0,2-0,5 | 250 | 1,0 |
| Impregnated Asbestos/Cast Iron- Steel | 0,12 | 0,32 | 350 | 1.0 |
| Carbon-graphite/Cast Iron- Steel | 0,05-0,1 | 0,25 | 500 | 2.1 |
| Kelvar/Cast Iron- Steel | 0,05-0,1 | 0,35 | 325 | 3,0 |
What is a good coefficient of friction for brake materials?
Typical dry coefficients range from 0.2 to 0.6 depending on the material combination and operating conditions.
Why is thermal conductivity important in brake materials?
High thermal conductivity helps dissipate heat generated during braking, reducing wear and preventing failure.
Are asbestos brake materials still used?
No. Asbestos materials are no longer used due to serious health risks and have been replaced by safer alternatives.
What materials are commonly used in modern brake systems?
Modern systems use composites such as carbon-based materials, Kevlar, ceramics and metallic blends.