Composition of brake system
The brake system generally consists of the brake pump, brake fluid, brake oil pipe, ABS system, brake calipers, brake pads, and brake discs from top to bottom.
The hydraulic brake system mainly applies Pascal's law, which is explained in the encyclopedia as follows: "Pascal's law can only be applied to liquids. Due to the fluidity of liquids, the pressure change that occurs in a certain part of the stationary fluid in a closed container will be transmitted in all directions with the same magnitude. According to Pascal's law, applying a certain pressure on one piston in a hydraulic system will inevitably produce the same pressure increase on the other piston. If the area of the second piston is 10 times that of the first piston, then the force acting on the second piston will increase to 10 times that of the first piston, and the pressure on the two pistons will be equal." Before understanding the structure of hydraulic brake systems. Understanding its basic principles helps to comprehend.
Brake pump
The working mode of the brake pump relies on the brake rod as a lever. When the rod is pulled down, it pushes the piston to squeeze out the brake oil from the upper pump and apply pressure to the lower pump in the brake caliper, causing the brake pads to come into contact with the brake disc and generate braking force.
The brake pump is mainly divided into two types: direct push and side push. There are many materials and manufacturing processes for the brake pump, and the selection of materials and processes is mainly influenced by cost and weight. The most important and technically advanced component of the brake pump is the pump piston oil seal. The two most important data for matching the entire brake system are the piston diameter and piston stroke (described in detail later)
(1)Side push up pump
By leveraging the principle of leverage, the force applied vertically to the lower pull rod is converted into lateral thrust. Alternatively, it can be understood that the direction of motion of the pull rod is perpendicular to that of the upper pump piston. However, it should be noted that since the pull rod is undergoing rotational motion, the part of the pull rod that contacts the piston is also undergoing rotational motion, resulting in a nonlinear relationship between the motion stroke of the pull rod and the stroke of the upper pump piston being pushed. Therefore, in practical use, the feel of the side-push brake pump to the human hand is also nonlinear. Similarly, as the pull rod is pulled down, the corresponding piston advancement distance decreases (for example, at the beginning, the pull rod is lowered by 1CM, and the piston is advanced by 1CM; at the end, the pull rod is lowered by 1CM, and the piston is advanced by 0.5CM). This nonlinear setting can, to some extent, prevent the danger of a person squeezing the brake hard due to nervousness in emergency situations. The side-push pump structure is compact, small in size, and low in production cost, making it less likely to damage the upper pump piston and piston cylinder in the event of a fall or other damage. Therefore, side-push pumps are commonly used in original equipment vehicles and are suitable for riders of various levels.
Side-push can also achieve a linear feel through structural optimization, but the cost is higher than that of direct-push. So, it's not that side-push lacks a linear feel, but rather that the cost of achieving a linear feel is too high, making direct-push a more practical choice. However, there are now high-end side-push designs with vintage aesthetics, which are excellent in both appearance and feel, and offer great value for money.
(2) Direct-push pump
Utilizing the lever principle, the force applied vertically on the pull rod is proportionally amplified and directly acts on the upper pump piston. The direction of movement of the pull rod is consistent with that of the upper pump piston. Thanks to this structure, the direct push of the upper pump provides a very linear feel, commonly used in sports cars and racing cars, and often in high-end modifications. The disadvantage is high cost, and due to the vertical arrangement and relatively large size of the piston, an external oil cup is usually required, which can easily damage the piston and cylinder block during a fall or rollover, resulting in overall damage.
Due to the advantages and disadvantages of their respective structures, there is a differentiation in the usage scenarios of the two. However, not all direct-push pumps are better in terms of hand feel than side-push pumps, nor are all side-push pumps lighter and smaller in weight than direct-push pumps. One cannot blindly choose a pump based solely on its structure. Instead, specific analysis should be conducted based on factors such as design, material, and data, while also considering budget.
