Big brake kits are often times the most overlooked, but most important, upgrades when it comes to customization. Aside from the aesthetic beauty of having large rotors landscape your new wheels, brakes play a key roll in stopping vehicle with large hp gains, bigger wheels or simply for those who live in cold-weather conditions.
Upgrading to a big brake kit generally means that you run a larger brake disc, a caliper with more clamping force, as well as brake discs, which are either vented, slotted or sometimes a combination of both. But to better understand braking technology and the important factors to consider, we were able to get some very useful information from Dan Barnes over at StopTech. The following information will give you a better understanding on what to look for as well as some of the key components of what make big brake upgrades so important.
While almost every current passenger car is capable of a single stop from maximum speed at or near the limit of tire adhesion, the braking systems of most passenger vehicles and light trucks and some sports cars are not adequate for hard or sport driving or for towing. Most stock brake systems lack sufficient thermal capacity; the system's ability to absorb and transfer heat by conduction, convection and radiation into the air or surrounding structure during severe driving. In addition, many stock calipers and their mountings are structurally not stiff enough at higher line pressures and the resultant higher clamping loads.
That's why even though there's enough front brake torque to lock the front wheels at highway legal speeds, caliper flex at the increased system pressure required to stop the car from high speed may prevent wheel lock-up. Needless to say, most OEM brake pads are also not designed for severe use, since cold stopping performance and quiet operation typically are considered more important to new car buyers.
There are a few basic facts that must always be kept in mind when discussing brake systems:
1) 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 advertising, 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 3,500-pound car traveling at 100 mph in eight seconds is 30,600 calories/sec or 437,100 BTU/hr or equivalent to 128 kW or 172 Hp. The disc dissipates approximately 80-percent of this energy. The ratio of heat transfer among the three mechanisms is dependent on the operating temperature of the system.