What is brake fade and what causes brake fade?

obi_waynne

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This phenomenon known as brake fade can be quite unexpected and lethal and I would hazard a guess that 1 in 4 cars are likely to experience brake fade to some degree. Brake fade manifests itself by a spongy feel on the pedal and little or no braking force. Do not confuse brake fade with bad brakes or a mechanical fault as it applies to brake systems in relatively good condition.

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T9 man

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I have had this on occasion and I take the car straight to the garage, the problem is usually something different each time but the fault is always corrected before I leave the garage.
 

TCJBOLDIE

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BF can be due to a couple of things, degraded fluid that has taken in moisture and the heat transfer from the discs boils the fluid pushing the pistons onto the pads and that results in a spongy pedal, poor quality/unsuitable pads that are overused at the track, or long downhill descents.

If you use your brakes hard and often then FWIW I would upgrade the fluid to a better quality higher temperature type like Motul RBF 600 and bleed them more often .
 

old-git

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Essex
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Elan & Robin Hood
The classic definition of brake fade is when no matter how hard you press the pedal very little happens in the braking department but quite a lot in the trouser department. The pedal feels fine but nothing much happens. This is caused by too much heat which releases gases from the pad material forming a barrier between pad and rotor. Slots and/or holes can help dissipate the gases reducing the risk of fade. Using a harder pad material can also help but this will result in a reduction in braking efficiency at normal road speeds as they need to be hot in order to work properly.

The spongy brake 'fade' isn't actually fade. The pad and rotor friction coefiicient hasn't changed but the pressure that the pedal is able to exert has been reduced by contaminates in the brake fluid, usually water. Brake fluid is hygroscopic, meaning it absorbs water. This can build up over time to a level that when heavy braking occurs the heat generated boils the water turning it into vapour which is compressable, hence the spongy feel to the pedal.

For road use, simply changing the fluid reguarly (realistically, every couple of years is fine) is all that is required to keep that hard pedal feel.

For track use, where temperatures can get very high, a higher boiling point fluid is advantageous. Be careful, however, if considering a silicone based fluid. Although not hygroscopic it can reduce the hardness of standard road car brake system seals resulting in an early failure.
 

RobBentley

The Torque Meister
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0
From
Kent, UK
Car
Audi RS6 C6 Saloon
I got terrible brake fade, and then brake judder not long after having new discs/pads at the front. Turned out Audi had helpfully supplied two nearside discs, so the offside got far too hot (cooling vanes running backwards). My fault, should have noticed - but you live and learn.
 

old-git

Moderator
Points
617
From
Essex
Car
Elan & Robin Hood
I got terrible brake fade, and then brake judder not long after having new discs/pads at the front. Turned out Audi had helpfully supplied two nearside discs, so the offside got far too hot (cooling vanes running backwards). My fault, should have noticed - but you live and learn.
Crikey, that is very easy to miss.
 

TCJBOLDIE

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Brisbane
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JB Starion
Always check the heat operating range of the pads to select one that is suitable for whatever you use the car for.
 
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