Views: 0 Author: Site Editor Publish Time: 2021-10-20 Origin: Site
Although nearly all passenger cars today are capable of stopping maximum speed in a single pass at or near the limits of tire adhesion, most passenger cars, light trucks and some sports cars have braking systems that are inadequate for hard or sporty driving or towing. Most common braking systems lack sufficient thermal capacity - the ability of the system to absorb heat by conduction, convection and radiation and transfer it to the air or surrounding structures during strenuous driving. In addition, many spare calipers and their mounting on structures are not stiff enough under higher line pressures and sufficiently high clamping loads. That's why even with enough front braking torque to lock the front wheels at legal highway speeds, the calipers may prevent wheel lock under the increased system pressure needed to bring the car to a stop at speed. But increasing the efficiency of the pressure system may help ameliorate these problems. For new car buyers, there is a lot of common sense that you should know ahead of time. Below we will give you an overview of what provides pressure to the brake system for braking purposes.
How the hydraulic system works.
Go further
Mechanical Pedal Ratio
Brake Line Pressure
Clamping force
Braking Torque
The brakes work under hydraulic pressure. If the brake system is unable to build up the pressure needed to operate the system, then your pedal will feel strange. In some cases, it will be floppy. In other cases, the brakes must be applied.
When you depress the brake pedal, the master cylinder delivers fluid to the lines, which creates pressure. This activates a caliper that squeezes the rotor on each wheel between the brake pads. Drum brakes work similarly, but the hydraulic pressure causes the actuator to press the shoes against the sides of the drum, which slows the wheels.
Please note that this will not happen if the line pressure is not sufficient. Similarly, if water enters the system, the result may be the same. The boiling point of water is lower than the boiling point of brake fluid. When it heats up on the brake, it evaporates, which creates air in the line (and allows compression-brake fluid cannot be compressed).
To go further, it is necessary to understand some of the physics involved, which requires some definitions.
1. Mechanical Pedal Ratio: Because no one can push the brake master cylinder directly hard enough to stop it, the brake pedal is designed to multiply the driver's effort. The mechanical pedal ratio is the distance from the pivot point of the pedal to the effective center of the foot pad divided by the distance from the pivot point to the master cylinder pushrod. Typical ratios are 4:1 to 9:1. The larger the ratio, the greater the force product (longer pedal travel).
2. Brake Line Pressure: Brake line pressure is the hydraulic pressure that actuates the brake system when the pedal is depressed. Measured in imperial units of pounds per square inch (psi), it is the force applied to the brake pedal (in pounds) multiplied by the pedal ratio divided by the area of the master cylinder (in square inches). For the same force, the smaller the master cylinder, the higher the brake line pressure. Typical brake line pressures during stopping range from less than 800 psi under "normal" conditions to a maximum pressure of 2000 psi under maximum force.
3. Clamping force: caliper clamping force is the force exerted by the caliper piston on the brake disc. In pounds of clamping force, it is the product of the brake line pressure (in psi) multiplied by the total piston area of the caliper (in square inches). This is true regardless of whether the caliper is a fixed or floating design. Increasing the pad area will not increase the clamping force.
4. Braking Torque: When we talk about results in the braking department, we are really talking about braking torque - not line pressure, not clamping force, and certainly not fluid displacement or fluid displacement ratio. The braking torque on a single wheel is the effective disc radius in inches multiplied by the clamping force multiplied by the coefficient of friction of the brake pad on the disc divided by 12. The maximum braking torque on a single front wheel typically exceeds the output of the entire torque-typical engine.
The car is mainly supplied with pressure by the hydraulic system, and when you are using the hydraulic system, you need to prevent the entry of air. We recommend that you learn more about car brakes before you buy.
