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When to Replace Brake Pads
Brake pads are a consumable part of the brake system and need to be replaced before the friction material has been worn to the backplate. A general rule is to replace them when there is 2 mm of material left. But their condition can deteriorate during use. In many cases, this will not have a significant effect upon performance. There are cases where the pads should be replaced immediately.
Contamination
The friction material appears contaminated with oil or grease that could have been caused during maintenance or from a caliper leak.
This can cause a loss of friction and for the vehicle to pull to one side during braking.
The cause of the leak needs rectifying and the complete set of pads needs replacing.
Surface cracks
Due to the formation of the material, surface cracks pose no safety risk, even in grooved brake pads, giving no disadvantage in performance or stability.
Friction material detachment
Friction material can partly or fully detach from the backplate.
There are many potential causes including handling, corrosion, constant thermal stress, backplate deformation, mechanical overloading and manufacturing faults.
The complete set of pads needs replacing.
Edge crumbling / break-off
Due to the formation of the material, edge crumbling or break-off poses no safety risk unless sufficient material is lost to affect general performance.
There are many potential causes including handling, corrosion, excessive heat, contamination and manufacturing faults.
The complete set of pads should be replaced when 15% of the material has been lost.
Material pockets
Due to the formation of the material, localized losses of material pose no safety risk unless sufficient material is lost to affect general performance.
This may be caused by stiction corrosion.
The complete set of pads should be replaced when 15% of the material has been lost.
Glazing
Glazing can be caused through harsh bedding-in or intermittent high pad temperatures.
No action is required for light glazing.
Heavily glazed pads should be replaced as an axle set.
Backplate deformation
Backplates can become deformed due to incorrect fitting of the pads.
It can cause the friction material to become detached.
The complete set of pads needs replacing.
Scoring / uneven wear
The friction surface has an uneven wear pattern due to disc scoring or incomplete contact between pad and disc.
It can cause brake noise and/or judder.
If noise or judder is experienced, replace both discs and pads.
Technical article provided by Alcon Components Ltd. Published by AlconKits with permission.