Automotive Brake Calculator

 


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Brake Balance (or Brake Bias) refers to brake torque at the front wheels as a percentage of total brake torque. The calculated number shows the bias "under full braking", for the highest deceleration possible with the current vehicle setup, on clean and dry tarmac or concrete, with the tires working at their advertised friction coefficient. Dynamic weight transfer and aerodynamic down force at top speed (if applicable) are taken into this equation as well.

In order to achieve maximum deceleration (when all four wheels simultaneously begin to lock up) on a surface with less grip, the forward bias will have to be less! This "need" for a different bias on different surface conditions, is the reason why most race cars have an adjustable balance bar between both master cylinders, an adjustable proportioning valve, or both.

Note that this number = Weightfront @ Brakemax (weight distribution under maximum deceleration), but only when front and rear tires have the same diameter and friction coefficient.

A number higher than 100% indicates a situation where the rear wheels would lift off the ground. A situation that is easy to create with a "virtual vehicle", but not in the real world. For exceptions, click here. And here. See also: Dynamic Weight Distribution.

On wet or slick roads, brake bias needs to be adjusted in order to achieve maximum deceleration on that particular surface. The proportioning valve (sometimes called a bias valve) can help with adjusting the balance to work with the friction level of the road, but also with the weight of the load we might carry in the trunk (amount of gas left in the tank) or on the roof (load on roof rack), aerodynamic downforce or lift, etc. (in other words, all factors that influence weight transfer).

And many race cars have an adjustable balance bar that let you change the brake balance for different tracks with different grip levels or when the track gets wet (more rear brake torque and less front brake torque, compared to a "dry track setting").

Factors that always affect brake bias:

- Static weight distribution (between front and rear axle)
- Wheelbase
- Aerodynamic downforce
- Location of center of aerodynamic downforce
- CG-Height
- Radius of tires
- Friction of tires

Factors that only affect brake bias if M/C diameters are not adjusted to compensate for changes in these factors:

- Rotor diameter
- Friction of brake pads
- Total-caliper-piston-area per axle

In this calculator, the M/C diameters always represent a (hypothetically perfect) situation in which front and rear wheels lock up simultaneously, so changes in rotor diameter, friction of brake pads and diameter and number of caliper pistons will not affect the Brake Bias as calculated under these conditions.

 

Last Update: 04/12/2017
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