To determine deceleration g-forces, input initial speed, final speed, and the most accurate time elapsed in seconds as possible. Final speed does not have to end at 0 mph. Your initial speed and final speed inputs could be braking from 60 mph to 30mph for example.
This calculator uses the deceleration formula. Deceleration actually depends on many factors including weight and tire friction that are not included in this calculator. Deceleration just like acceleration is not constant for multiple reasons. The deceleration of a vehicle can be improved through weight reduction, increasing tire friction, and larger brakes that do not fade.
Anti-lock brake systems are designed to allow for maximum user braking without locking the wheels into a dreadful skid.
Drum brakes can sometimes be dangerous after periods of excessive braking which is why many times automobile manufacturers used front disc brakes in addition to cheaper rear drums because the front brakes would need better stopping ability due to the transfer of weight load up front. This is also why most cars with front and rear disc brakes have larger front disc brakes than needed in the rear.
To help with cooling, most disc brakes on performance cars are drilled and vented. Some aftermarket disc brakes are also slotted which is widely believed to cause better braking results at the expense of premature wear.
Popular aftermarket braking systems include Brembro brakes or Willwood brakes.