Brake pad 101

古惑強

http://www.sportscarboutique.com/Car%20Parts/BrakesPagid

Avoiding Brake Judder

During bedding and shortly after, some judder is quite normal but should disappear after 5 to 10 laps. Changing back and forth between two incompatible friction materials (e.g. racing brake pads of different brands or street pads) can cause uneven build-up of pad material on the disc surface and can consequently lead to brake judder. Judder is the result of a thickness variation in pad buildup on the disc surface. Brake judder can be from a barely noticeable vibration to a violent judder. When you install Pagid race pads on top of a layer of an incompatible pad material, bedding might take much longer or in worst case won't work at all. It can also result in sub-optimal brake performance.

Another reason for uneven pad transfer is called 'imprinting'. After coming to a complete stop with hot brakes (in the pits or after a spin), do not keep your foot on the brake pedal. The hot pads can leave a deposit behind that in turn again can cause judder and vibrations.


Bigger vs Smaller Pad

A larger friction surface will not improve stopping power. The amount of pressure applied, coefficient of friction and the disc diameter determine stopping force. A bigger pad does not apply more pressure, only the same pressure over a bigger area. The size of the pad matters in terms of heat capacity and wear rate. A larger pad will absorb more initial heat and has better wear characteristics.

古惑強

I think the sentence is trying to say is "provide that the overall hydraulic pressure is the same in either occasion, pressure over square inch (psi) would actually decrease due to the bigger brake pad area."

coupeelvin

"A bigger pad does not apply more pressure, only the same pressure over a bigger area."

Well... I don't quite understand: If the same pressure is applied to a bigger area, this means that pressure = P for brake pad of area = A, or area = B.
Then the friction = coeff. of friction x area
But, should the coeff. of friction be proportional to the pressure applied?
So, the friction should still increase.....

paul

回復 2# Simon

Just done it for my Punto, I used ATC.4pro racing, it is good but not long lasting, good racing characteristic always trade off by service life, be aware of this also. I use ATC normal .4 now.

Simon

我唸咁可以解釋點解迫力碟背損耗比面多.
可能因為個放氣咀係外面, 而迫力油系統有氣, 所以brake在外面唔夠responsive, 落迫力多數用了內皮, 所以輕迫力時就只蝕碟背.
我唸勤D換迫力油吧. 每年一次也不為過.