trying to understand braking systems. tell me if im on the right track, gleaned some info off of the stoptech website Options

[enderswift]

read this article : http://www.stoptech.com/tech_info/wp_rearb..._upgrades.shtml

it explains why balance always prevails. It also highlights a mistake that alot of people are making. Brakes dont do the stopping your tires do. Brakes only convert the rotational energy of the wheel into heat. So increasing the heat dissipating and storing potential of a brake system will yield more consistent and resilient brakes. a common upgrade path is to increase the diameter of their rotors. While this will increase thermal capacity, the downside is that larger rotors will ruin the brake bias, thus increasing stopping distance. I could go on...

long story short, in my opinion, big brake upgrades for our cars aren't really a good idea. Instead, installing high boiling point fluid, slotted rotors, and high temp pads will reduce brake fade (letting you beat on your car for longer) while maintaining oem brake bias (which means ur car will be predictable and easy to control). If you mess with brake bias by changing piston/rotor diameter, you will either induce excessive understeer, or oversteer ( you really have to f up with the setup to cause oversteer in a celica).

[enderswift]

ok apparently all cars have brake proportioning valves already installed. The reason for lies in the way weight shifts during braking. while max braking, as much as 30% of rear mass shifts forward causing an 80% front , 20% rear distribution. If there were no proportioning valves, then the rear brakes would get just as much hydraulic pressure as the fronts. 50% brake pressure coupled with only 20% mass on the rear wheels would result in rear wheel lock up; ie oversteer. this is very very bad.

for simplicity assume no abs:

If you just plan to upgrade your front brakes, you will have to adjust the bias to compensate. imagine you want to shorten your stopping distance so you get bigger rotors and multipiston/larger piston calipers. The combination of those components will result in a higher clamping pressure with respect to the drivers input compared to the stock setup. The result is the wheels will lock up with less input from the driver. The problem with this is that now the fronts lock up alot sooner than before, while the rears still spin. This means that the whole mass of the car is trying to be stopped by just the two front tires. Thats alot to ask of those tires. ideally, you would have all four tires exerting resistance to the pavement. To do this, you must adjust you bias so that the fronts dont lock up until the rear tires are at their limit. Otherwise you'll understeer all over the place and your stopping distance will actually increase. another way to counteract this is to proportionally upgrade the rears as well so that oem bias is restored. unfortunately this cost $$$

lets look at the benefits and downsides of a big brake setup:
1. the benefit is a large increase in thermal capacity (your car will be able to take a huge beating while still being predictable)
2. less input from the driver means you have an easier time modulating the brakes, IE greater control

downsides:
1. more rotation mass and unsprung weight. This means more of your engines ponies are devoted to overcoming the mass of the car. this = slow
2. more expensive, larger calipers and rotors front and back are EXPENSIVE (for quality parts).... never buy cheap brake parts!
3. more difficult to setup. Dont think slapping on larger components will maintain your cars bias. several sets of math calculations must be involved to tell you how to adjust your proportioning valve. failure to do this WILL result in understeer/oversteer.

In my opinion, the benefits of a big brake setup dont outweigh the downsides. Especially when the same benefits can be had with a milder alternate tuning route

Another way to go about upgrading brakes is to understand that all brakes do is convert kinetic energy into heat. you should first replace brake fluid with a high boiling point substitute, get vented (not drilled) rotors, find pads with a linear coefficient of friction across a wide range of temperatures, and steel braided lines. The fluid, rotors, and pads will take care of any heat related issues, while the lines will give the driver greater pedal feel. All this while maintaining a stock bias and keeping unsprung/rotational mass at a minimum. Compare that to downsides associated with larger components. THE only time you should consider upsizing is if there are still heat related issues such as fade. Otherwise supersizing the front is a counterproductive expense that demands ALOT of tweaking to properly balance the rear. Likewise, even if you upgrade the rear at the same time, figuring out the clamping force of each caliper is still necessary to restore the bias. Dont assume that upsizing everything will maintain balance, make sure by learning some basic algebra and physics. Since my fingers are about to fall off, swing by the stoptech website to find those equations and a more in depth explanation than what i provided.