Testing shear strength
Many publications about the ECE-R90 test mention shear strength. What exactly does that mean?
Shear tests are used to check the strength of a friction material. An increasing force is applied to the friction lining until it shears in two. This test helps to ensure that the product fulfils the legal requirements. Failure to comply with the minimum requirements could result in a sudden complete failure of the brake system during braking.
Friction lining after a shear test
Base friction material surface
Sheared-off friction material
The drawing below illustrates the test method:
Legend to illustration:
- 1 Brake pad
- 2 Shear force gauge
- 3 Counterholder
- 4 Mount
- 5 Compression force
- 6 Shear force
The brake pad (1) is placed in a mount (4) and held in place by a counterholder (3) with light pressure. The shear force gauge (2) is pressed against the friction mass and the shear force is continually increased until the friction mass shears in two. The shear strength is the quotient of the measured force at the time of shearing and the cross-section of the friction lining’s base surface.
EU regulation ECE R90 requires a shear strength of at least 250 N/mm². All of our products achieve significantly higher readings.