BRAKE PAD FAILURE MODE FIELD STUDY
The Global Brake Safety Council recently conducted an engineering field study of 3,200 discarded brake pads to find out if the pad had failed or just worn past specifications. The study classified each of the pads into five distinct categories or failure modes. The geographic location of where the pad was collected was also taken into account to help make the connection between corrosion of the backing plate, shims, and attached hardware.
Failure Mode 1 – No Apparent Visible Cause
66.9% of these brake pads showed more than 50% of friction material remaining with no visible signs of delamination/separation, according to the survey. This trend could be explained by uneven pad wear between the inner and outer pads and even differences in pad wear on each side of a suspension. This type of uneven wear can be caused by failure to properly service the caliper and bracket during pad replacement.
Failure Mode 1
Failure Mode 2 – Friction Worn to Backplate
The friction material was worn to the backing plate with evidence of galling and contact with the rotor in 5.6% of the cases. This type of failure mode can damage the rotor and require replacement or refinishing on a lathe.
Failure Mode 2
Failure Mode 3 – Excessive Rust
The field study found excessive corrosion of the shim, pad abutments, and clips in 11.0% of the pads. Corrosion of these elements can lead to noise, drag, pad wear and possibly shim migration that could cause the shim to come in contact with the rotor.
Failure Mode 3
Failure Mode 4 – Pad Edge Lift
Noted in 11.2% of the cases, the pads showed signs of edge lift or rust jacking due to corrosion with a partial gap to the full-width gap of the backing plate. This type of failure mode can cause noise, vibration, and roughness. Also, this condition can cause the friction material to separate from the backing plate leading to loss of braking power and vehicle instability.
Failure Mode 4
Failure Mode 5 – Broken/Separated Friction
A substantial part of friction was separated from the pad or backing plate in 5.3% of the cases. This means that the vehicle the brake pads came off had a compromised brake system with significant increases in stopping distance and possible stability issues under heavy braking.
Failure Mode 5
The authors of the study concluded: “Continued use of sub-standard product and material, coupled with the use of “black steel” which is hot rolled steel that has not gone through the pickling and oiling process to remove impurities, rust, scale, and other contaminants and a lack of regulations or industry-standard practices can directly lead to the above-mentioned failure modes.”