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Old 01-10-2003, 01:48 PM   #1
Gravel-Fun
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Join Date: May 2002
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2000 Impreza RS
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Question What exactly causes brake fade?

I want to be clear on the cause and best cures by those who are familiar with this issue.

Is brake fade caused primarily because the rotor is so hot, the pads can no longer get a proper grip?

Do the cooling duct with hoses from the front of the car to the back of the rotor, improve the situation much? I have seen the NACA ducts, and wonder about their effectiveness.

Thanks in advance for your input.

Gravel-Fun
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Old 01-10-2003, 03:44 PM   #2
Jon Bogert
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Is brake fade caused primarily because the rotor is so hot, the pads can no longer get a proper grip?
Pad fade is because the pads are too hot. There are two kinds of fade: pad fade and boiling fluid. If your pads fade, just get higher temp pads. If the fluid boils, there are little things you can do like installing stainless or titanium shields behind the pads, using absurdly expensive fluid, etc. But basically, if your fluid is boiling, your system has run out of capacity and you need better cooling (remove dust shields, add ducts, etc) and/or components that have more thermal reserve such as thicker, larger rotors.
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Old 01-10-2003, 04:29 PM   #3
MrAWD
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Default Re: What exactly causes brake fade?

Quote:
Originally posted by Gravel-Fun
I want to be clear on the cause and best cures by those who are familiar with this issue.
The process of braking is actually conversion of the kinetical energy that the car has to the heat that gets to be dissipated through the brakes. Basically, when you start braking, energy conversion starts and rotors, pads, and calipers get more and more heat in them. If there is no way to take that heat out from the system, eventually, you will get to the point when the system is saturated with the heat and it can't take any more. That is where you get the fade.

Of course, brake could happen due to the boiled water in your oil and that just lower the amount of the clamping force that you have in the calipers. Basically, air (once it gets there) is compressible (unlike the fluids) and most of the pressure that gets created by your foot, goes for the compression of that air.

Brake pads with higher coefficient of the friction will transform the energy quicker than the regular pads (so they will get to the overheating spot sooner) and if the system is not balanced well they will fade quicker than the normal pads.


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Old 01-10-2003, 05:18 PM   #4
IXLR8
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Originally posted by Jon Bogert
basically, if your fluid is boiling, your system has run out of capacity and you need better cooling (remove dust shields, add ducts, etc) and/or components that have more thermal reserve such as thicker, larger rotors.
That of course assumes you have fresh fluid that has not absorbed any water and therefore is operating at the temps the mfr intended... The first thing to do if you are boiling fluid is to put in/make sure you have fresh fluid... then move on the the other mods if that doesn't help.

By the way, symptoms of the two types of fade are different... with pad fade, the pedal stays firm, but you just don't slow down when you apply the brakes... With fluid fade (boiling) your pedal gets soft and then turns to mush as it eventually goes completely away.

You should note too, that if you've boiled the fluid, even though your pedal will firm up once things cool, you've lowered the temperature at which you'll boil the fluid the next time you heat up the brakes... at the least, you need to bleed off the fluid at the end of each line (the stuff closest to the calipers where the greatest amount of heat was...)
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