hydraulic brake design calculations process


In an automobile the main purpose of braking system is to stop the vehicle in a short period of time and distance (in order to avoid accidents ) by converting the kinetic energy of the vehicle into heat energy ,before dissipated into atmosphere ,thanks to the Regenerative braking system technology we can reuse the heat energy generated.

So to achieve that objective efficiently we have different types of braking arrangements and actuation mechanisms. I will not go into these types here, our main goal being the braking system calculations for light weight vehicles like Go kart or Baja atv (all-terrain vehicle).

Almost all light weight vehicles nowadays use the hydraulic braking system, in which the brake is actuated by means of hydraulic fluid.


The system has many advantages which made it the most widely used in commercial vehicles and some trucks.

Some of the advantages of the system are as follows:

  • The hydraulic fluid exerts equal pressure (Pascal’s  fluids principle) on all the wheels;
  • Simple in construction;
  •  Need few components ( master cylinder ,brake pipelines brake caliper, brake disc) making the assembly weight less;
  • The system is mostly self-lubricating;
  • The pipelines can be bent and shaped according to the underside of the body structure;
  • The system commonly use a Tandem master cylinder from which different lines go to different section of the vehicle (say front and rear wheels) and it ensure reliability of the system ,if one section fails chance are the other is working.

Moreover ,aside those advantages we do have some disadvantages of the system ,the most common being even slight leakage of air into the brake lines affects the whole system and lead to failure.

While designing the system for commercial vehicle or trucks separate mechanical linkage has to be used for the parking brake.


In the braking system calculations some jargons are used, if misunderstood can make the system design very difficult.  

Let dive into them

Brake pedal ratio

It’s the ratio of leveraging the brake pedal to the master cylinder.

The ratio is generally between 5.1:1 to 7.1:1 mean 1kg applies at brake pedal is 7.1 times at wheels, it’s a mechanical advantage.

Learn how to calculate the brake pedal ratio

Effective area of the master cylinder piston
master cylinder the bore diameter is use to find effective area of the cylinder in hydraulic brake design calculations
image clearMechanic.com

It’s calculated using the formula   where ‘D’ is the master cylinder bore diameter can be found in the specifications of the master cylinder.

Effective radius of brake disc

It’s the Centre of the brake pads by area .it can be found from the ratio  disc useable outside diameter /disc useable inside diameter

Generally for brake disc ranging from 190mm to 200 mm it’s around 160mm to 170mm.

After understanding these jargons my recommendations will be, before starting the calculations make sure you have:

  • An idea of the final weight of the vehicle (with the driver and without) or assume;
  • The specifications of the master cylinder or tandem master cylinder (specially the bore size) you are going to use;
  • The specifications of the brake caliper (specially the bore size); is it single or double piston?
  • Brake disc diameter from which the effective radius of brake disc can be determine;
  • you know the distance from front axle to center of gravity, distance from rear axle to center of gravity and also the height of center gravity from ground.

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I hope you enjoy this post and it can help you design your vehicle better. If you like the post pleases comment and share, and if you will like us to cover any related topic suggest, we will do our best to satisfy your queries.

See also: Go kart steering calculations with ackerman steering geometry

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