Shared post from 'G35Driver' by WhosUrBuddiee from thread 'BBK Myths':

I have seen younger and younger people joining the G35 community and often believe several fundamentally incorrect principles about their cars. One of the biggest being the belief that Big Brake Kits actually decrease stopping distance. It should be clear to everyone that BBKs do not decrease your stopping distance at all. The actual purpose of BBKs is to dissipate heat (and improve visual appearance).

There are a few basic facts that must always be kept in mind when discussing brake systems:
1) First and most importantly. The brakes don't stop the vehicle - the tires do. The brakes slow the rotation of the wheels and tires. This means that braking distance measured on a single stop from a highway legal speed or higher is almost totally dependent upon the stopping ability of the tires in use - which, in the case of aftermarket modification, may or may not be the ones originally fitted to the car by the OE manufacturer.

2) The brakes function by converting the kinetic energy of the car into thermal energy during deceleration - producing heat, lots of heat - which must then be transferred into the surroundings and into the air stream.

The amount of heat produced in context with a brake system needs to be considered with reference to time meaning rate of work done or power. Looking at only one side of a front brake assembly, the rate of work done by stopping a 3500-pound car traveling at 100 Mph in eight seconds is 30,600 calories/sec or 437,100 BTU/hr or is equivalent to 128 kW or 172 Hp. The disc dissipates approximately 80% of this energy.

3) Repeated hard stops require both effective heat transfer and adequate thermal storage capacity within the disc. The more disc surface area per unit mass and the greater and more efficient the mass flow of air over and through the disc, the faster the heat will be dissipated and the more efficient the entire system will be. At the same time, the brake discs must have enough thermal storage capacity to prevent distortion and/or cracking from thermal stress until the heat can be dissipated. This is not particularly important in a single stop but it is crucial in the case of repeated stops from high speed - whether racing, touring or towing.

4) Control and balance are just as important as ultimate stopping power. The objective of the braking system is to utilize the tractive capacity of all of the tires to the maximum practical extent without locking a tire. In order to achieve this, the braking force between the front and rear tires must be nearly optimally proportioned even with ABS equipped vehicles. At the same time, the required pedal pressure, pedal travel and pedal firmness must allow efficient modulation by the driver.

5) Braking performance is about more than just you brake size. In order for even the best braking systems to function effectively, tires, suspension and driving techniques must be optimized.

All modern cars are equipped with Antilock Braking Systems. ABS is an electro-mechanical control system designed to monitor and influence wheel dynamics, and ultimately vehicle dynamics during braking maneuvers. In order of priority, these systems are intended to enhance vehicle 1) stability, or the prevention of oversteer 2) steerability, or the prevention of understeer and 3) stopping distance. Typical systems consist of 3-4 wheel speed sensors, an ECU containing the algorithm processing the wheel speed information, a series of solenoid-driven valves, and a pump-motor subsystem which can be actuated to interrupt and release brake fluid pressure from the wheel-end brake components (calipers and such).

To summarize, for two cars with the same weight, tires, and brake pad coefficient of friction - the stopping distances will be the same, regardless of how big the rotors are or how many pistons you have. BBKs are only to dissipate heat and reduce brake fade under repeated braking conditions.

If you want to improve your stopping distance, get better tires.
If you want to reduce brake fade, get better pads.
If you want to prevent vapor lock, get better brake fluid and lines.
If you want to improve visual appearance of your car, get a BBK.