Brakes

[NoHachi]

Ok, this forum is desperately in need of some braking tech:
First up we need to distinguish between 3 important elements:

1. Braking power
2. Braking capacity
3. Brake feel

1. Braking power, this may seem strange but the braking power is usually more then adequate on even the smallest systems. To test whether you have enough braking power find a abandoned stretch of road, accelerate to 150+km/h and slam on the brakes. If the tires lock up then the brakes provide enough power to overcome the tires and these effectively become the systems restrictions. Thats probably the single most influential factor in braking: the tires. Upgrade before anything else.

Braking power is a function of line pressure and brake cylinder surface area. Switching to 4 pot brakes optimizes the pad area thats used, but why bother when a single pot is sufficient to lock up the tires?

2. A more important aspect of brakes is their braking capacity. Basically not just whether you can lock the tires, but also how many times in succession you are able to do this. The job of the brakes is to dissipate kinetic energy away from the car. It does this by converting it into heat: thats where the problems start. When everything heats up to much fading occurs. Whats fading you say? Ill explain:
Basically fading is every situation where braking effort is not converted into braking force: You pump the pedal, but nothing happens....
There are two forms of fading that generally occur during racing situations: padfade and line fade.
Padfade is a result of a brakepad being heated beyond its effective temperature range. Performance quickly deminishes and the pad surface can glaze over. When this happens the pads put down irregular friction material onto the discs, causing whats usually referred to as disc warpage (but its not). The solution is simple: use a appropriate pad material for the given situation. high temp(low cold bite)for racing, low temp quick initial bite (oem) for street. Whatever the pad YOU MUST MAKE SURE TO FOLLOW THE BEDDING IN INSTRUCTIONS EXACTLY! It can make a tremendous difference in pad and disc life.
The second form of fade is line fade. In this situation the fluid inside the calliper is heated beyond its boiling point. Compressible air bubbels are formed and braking pressure is put into compressing these bubbels, not stopping the car. There are several fixes for these problems:
Change the brake fluid often!! best performance upgrade you can do. When the fluid has reached high temps once, it wil never be as good as before. Change to a high temp fluid: Dot4 or DOT5.1 are both fine. Dot5.1 needs a little less maintenance but costs slightly more. DOT5.1 high temp is more readily obtainable though.
Provide more cooling to the brakes; ducts etc are noticable!
Enlarge the thermal capacity of the brakes: By providing more steel that can absorb the heat, and more area to dissipate heat, the capacity of brakes can be improved. Thats why big fat callipers and discs work.

3. Brake feel: This where the subjective part of the story starts. Brake feel is something that is difficult to measure. Usually its about the ease with which the brakes can be applied and held at the traction limit. Logically the smallest possible brakes should be ideal. The stroke of the brakes is largest so it should be easier to controll them.
In practice things are not that simple. Novice drivers seem to prefer the big capacity, short stroke brakes, stating that they feel more secure. usually its noticable in their laptimes too.

So basically big brakes are a worthwhile goal: You increase the systems thermal capacity and improve brake feel. They look good too. It comes at a price though...
Experienced drivers can achieve the same results with just a fluid and pad change and perhaps a couple of discs. Whatever way you figure it, its a much cheaper way of doing things. Your driving style should change to suit. Firm braking application when needed and just enough to slow the car down to the nessesary speed. No dragging on the brakes, short and decisive!
Big brakes usually come with a unsprung weight penalty. This will make it more difficult for your suspension to handle irregularities in the road. The effect gets even worse when you start lightening the car and the sprung/unsprung weight ration changes even further. you start to lose grip over road irregularities and the ride comfort gets worse. this is specifically noticable in AE86's with that heavy rear axle and usually heavy ass wheels.

Most people don't need bigger brakes, but just think they do. Thats fine, but the money could be better spent at other performance modifications that you use more often.