Brake Balance (or Brake Bias) refers to brake torque at the front wheels as a percentage of total brake torque.
The calculated number shows dynamic bias "under full braking" and the highest deceleration possible for the current vehicle setup, on clean and dry tarmac or concrete, with the tires working at their advertised friction coefficient. Dynamic weight transfer under full braking and aerodynamic down force at top speed (if entered) are taken into this equation as well.
Note: Most brake bias calculators on the web only give you static brake bias, a number that tells you the bias based on brake torque at the front and rear wheels, only taking into account rotor size, piston area and brake pad friction (and master cylinder size, but only in dual MC systems with different front and rear master cylinders). This could be of value when evaluating the effect of hardware changes on your static brake bias, or if you know what static bias number you're after, but a simple change of tires or moving the battery from the engine compartment to the trunk will already render this number useless, because these changes affect weight transfer under braking... Changes in weight transfer require changes in brake bias in order to maintain the maximum possible deceleration for the tires you (intend to) use.
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 for 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 Dynamic Brake Bias = 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 affect weight transfer while braking).
And many race cars have an adjustable balance bar that lets you change the brake balance for different tracks with different grip levels or when the track gets wet (more rear brake torque required and less front brake torque, compared to a "dry track setting").
Factors that always affect Dynamic Brake Bias:
- Static weight distribution (between front and rear axle)
Factors that only affect Dynamic Brake Bias if M/C diameters are not adjusted to compensate for changes in these factors:
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 number or diameter of caliper pistons will not affect the Dynamic Brake Bias but only the M/C diameter(s) and therefore line pressure(s).
|Last Update: 04/12/2023||
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