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2025
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Why do trucks need two air pressure gauges? You'll understand after reading this.
As one of the components of truck dashboard information, many truck drivers know that the air pressure gauge is related to braking, but they do not understand which specific part's value it displays. There are also many differing opinions online, making it difficult to discern what is correct. Today, let's talk about the specific meanings conveyed by the air pressure gauge.
● Importance of the braking system and hardware requirements for vehicles
To understand the meaning of the air pressure gauge, we first need to talk about the truck's braking system. It is one of the key areas of safety research and development for trucks. A good automotive braking system not only needs to have reliable braking performance but also aims to minimize the driver's workload as much as possible. According to statistics, traffic accidents caused by vehicle braking failures account for nearly 45% of the total in China, highlighting the importance of a reliable braking system.
In terms of hardware, the braking system needs to be equipped with components such as an air compressor, air dryer, air reservoir, and a four-circuit protection valve. Among them, the air compressor produces air for the braking system, the air dryer filters and dries the air entering the compressor to prevent moisture from affecting braking performance, the air reservoir stores the air needed for braking, and the four-circuit protection valve divides the vehicle's air circuits into four circuits: front brakes, rear brakes, parking brake, and auxiliary brake. (The arrows indicate the dual-line design for front and rear brakes.)
● Why there are two air pressures, the reason behind it, and the common forms of air pressure gauges
Currently, the majority of medium and heavy trucks in China use air brake systems. According to the piping, they can be divided into single-line and dual-line systems (single-line systems are no longer allowed due to poor safety). The front and rear brake circuits are independently distributed so that a failure in one circuit does not result in the failure of the entire vehicle's braking system. This is also the reason trucks are equipped with two air pressure gauges.
Single-dial dual-needle air pressure gauge, showing the brake pressure and the air tank pressure of the vehicle.
Dual dial pneumatic gauge, showing the pressure values of the truck's front brakes and rear automatic brakes respectively.
The LCD air pressure gauge displays the pressure values for the truck's front brakes and rear automatic brakes, respectively.
Currently, the common air pressure gauges on trucks mainly come in two forms (single gauge with double needles and double gauges with single needles). In addition, a few new models are equipped with LCD air pressure gauges. The single gauge with double needles usually has two red needles or one red and one white needle, while the double gauge with single needles mostly uses red needles.
Although air pressure gauges come in various forms, their principles are the same. They display the pressure values of the truck's front brakes and rear brakes, which is the most commonly used form on trucks today. There is also a type that shows the pressure during vehicle braking and the pressure in the air storage tank, but this is now quite rare.
● Editor's Note:
Truck drivers reading this should now understand the meaning of the air pressure gauge. It shows the pressure values of the front and rear brakes when the vehicle brakes. Additionally, the air storage tank operates simultaneously. Their only purpose is to provide real-time feedback to the driver on the vehicle's braking performance, offering greater safety assurance for the driver.
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