07
2026
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03
[Serious Misconception] Increasing the air volume of the main valve or relay valve will improve braking performance
Regarding truck braking issues, most drivers are deceived. Many roadside shops, for the sake of profit, replace certain original factory brake valve parts, which actually just increase the air volume of the master cylinder or relay valve, giving the impression that the braking force has improved.
● What exactly is the principle, and why does it feel like the braking is stronger?
Actually, it just ignores the part of the travel with small brake air volume and directly enters the travel with large air volume. It moves the section with stronger braking force forward, so that a light press of the pedal immediately engages the brakes, giving the impression that the brakes have improved.
Brake Master Cylinder
Initially, the approach was to polish the master cylinder piston or to add shims to achieve the above effect. This was probably the earliest form. The modified master cylinders follow the same principle, except that now the modification has been turned into a mass-produced complete product that can be directly replaced.
● Replacing modified valve components is actually not reliable
In fact, these aftermarket valves on the market work by increasing the air passage to shorten response time, which only makes the driver subjectively feel that the brakes have become stronger.
Some car owners even modify their cars as soon as they take them home, while others do so after the vehicle has been driven for a certain distance, due to brake component wear or reduced braking force caused by improper maintenance. At this time, they replace the original pump valves with aftermarket valve components. Braking is not one-sided; it is an overall system that must maintain coordination, especially in the case of trailers.
Replacing the brake valve
We all know that the brakes of the trailer and the main vehicle must work in coordination to ensure effective braking. After replacing or modifying the valve components, the overall braking coordination of the vehicle is disrupted.
Brake Pads
After modification, the linear increase in braking force almost disappears, leading to a phenomenon some car owners describe as locking up the brakes with a light press, while pressing harder has no effect. Because the modified parts increase the amount of air passage, the brake air pressure will also drop faster. For some cars that inflate more slowly, the brake pressure may become insufficient on downhill slopes, which is both dangerous and troublesome. Many car owners may have had the experience that after modifying the valve parts, the brake drums become noticeably less durable.
Brake drum cracking often occurs; sometimes, newly installed brake drums will crack after only a short distance and have to be replaced. At the same time, the vehicle's braking distance does not shorten but actually lengthens. Blindly modifying the brakes without understanding why the braking performance has worsened is not reliable.
● Proper maintenance is important for good brakes
In practice, poor braking is often a result of improper maintenance. For example, using counterfeit or substandard brake pads and drums, or neglecting regular maintenance of the brake air system, such as not periodically replacing the dryer; only replacing brake pads without maintaining components like the camshaft, all of which affect braking performance and stability.
Brake problems should be fundamentally resolved
If you do not fundamentally identify the reasons why the brakes are deteriorating and instead modify the valve components, you may feel that the brakes improve in the short term. However, after using it for a while, these issues will gradually become more pronounced, leading your brakes into a vicious maintenance cycle. No matter what you replace, it seems ineffective. Therefore, proper regular maintenance is the correct approach.
To summarize: the quality of your brakes is directly related to the driver's safety. While modifying valve components might seem to enhance braking and ensure safety on the surface, the actual quality of braking depends more on regular maintenance. Relying solely on changing a modified valve to solve the problem is unreliable.
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