Bedding in of Pads and Rotors

 

BEDDING IN OF PADS AND ROTORS

 When a vehicle has had both new rotors and/or just new pads fitted, there are two processes or objectives, to getting the brake system to operate at optimal performance. The first step is to make sure the disc face is clean of all oils/anti rust or any foreign matter like previous brake pad material. If the rotors are not being replaced then it is imperative that the disc is machined prior to the fitment of new pads- without exception.

The second step is heating (not cooking) the brake rotor and pads, to transfer the pad material evenly, onto the rotor face. This step involves performing a series of stops, so that the brake rotor and pad are heated steadily, to allow the transfer of pad material onto the brake rotor friction surface. The friction surface should be clear of all oils which are used to stop the rotor from rusting before being fitted to the motor vehicle. 

Whilst these will be burnt off, they risk transferring and possibly polluting the brake pad material and will definitely lead to a longer bedding in process.  

Whilst performing a series of brake applications to transfer the pad material, care should be taken to not come to a complete stop, as this can lead to the transfer of pad material unevenly on the disc at the point where the pad comes to rest on the friction surface. 

Standard road going vehicles; - from zero degrees to 450 degrees Celsius. 

A typical program of 8-9 brake applications, from 60km down to 10km p/hour, without any cool down in between would be sufficient. 

Performance pads on road going vehicles; - from zero degrees to 700 degrees Celsius. 

For performance pad materials, a further two sequences of ten stops will be required after a cooling down period between each cycle, to ensure that the pads have reached the required higher operating temperature to allow for the pad material to transfer effectively.

  • Please also note that due to the increased brake force generated by performance pads, it is essential that all slides and sides of pads that may come into contact with the caliper body, be greased with graphite paste like "Permatex nickel anti-seize" and we also recommend the fitment of brake shims. Performance pads on track and club use vehicles; - from 150 degrees to 900 degrees Celsius.

For race type material pads, we recommend the same 2 cycles of ten brake applications from 60km down to 10km as for performance pads, followed by 4 sharp brake applications from 140km down to 80km, to ensure the pad material has reached optimal operating temperature and therefore material has transferred onto the brake disc - proper bedding in, will reveal a discoloration on the pad edge where it comes into contact with the disc rotor face, as if it has been overheated (appx 2mm band).

Applicable to all applications and uses.

At all times during the bedding in process, care should be taken to not apply the brakes in a harsh manner or decelerate from high speeds, as this will corrupt the transfer of materials and lead to uneven material build up on the rotor surface, which in most instances will require machining to regain a flat rotor surface for optimal operation. (Disc thickness vibration-DTV-which leads to brake judder or vibration).

How will I know if they are bedded in?

The two major visual indicators are disc rotor discoloration and machining marks on the friction surface of the disc rotor.

  • 1) Disc rotor should have a slight bluish tint with a grey tint that indicates where the brake pads have come into contact with the rotor. Too much heat will cause the rotor face to be extremely blue and has been overcooked in the bedding in process.
  • 2) If there is still a shine on the rotor surface, then not enough pad material, has been transferred. 

Once brakes have been bedded in, it is also important, to keep them that way. If any brake pad is used below its adherent operating temperature over a period of time it will slowly remove the transfer layer on the rotor surface. Standard and especially performance pads, like to be driven a little more aggressively every now and then to maintain this pad material, on the rotor friction surface. Similar in effect to taking a city based car on a country run every now and then and noticing the change in the exhaust tail pipe color, go from black to grey as it operates at a different temperature, to what it has become accustomed.

  • Passive use of brakes over an extended period of time will in effect lead to “unbedded brakes”.


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