05
2026
-
10
Understand in three minutes what the experienced driver means by 'qi ding you'
We're quite familiar with air brakes and hydraulic brakes, and there's also a type called air-over-hydraulic brakes, which used to be common on Japanese trucks years ago. Air-over-hydraulic brakes, also known as air-assisted hydraulic brakes or pneumatic-hydraulic braking systems, use both air pressure and hydraulic mechanisms.
The regular power brake systems include air brake systems, air-over-hydraulic brake systems, and fully hydraulic power brake systems. The air-over-hydraulic brake system uses a combination of air and hydraulic pressure, and you can also think of it as a brake system where air brakes and hydraulic brakes are linked together.
The Mitsubishi T850 uses an air-top liquid brake system
Similar to the air brake, the front part of the air-over-liquid system, which is the source of driving force, also uses an air pressure system, but a hydraulic system is added after the brake air chamber (this hydraulic system is also similar to the hydraulic brake system) to act as the braking actuator.
The brake air chamber and the hydraulic master cylinder are connected in series. By converting air pressure into hydraulic energy, brake fluid is delivered to each wheel cylinder to create braking. Compared to pure air brakes, the brake air chamber in an air-over-hydraulic system is smaller and more compact in layout. The air-over-hydraulic brake system also has these advantages:
1. The air system pipes are shorter, which reduces lag time;
2. The hydraulic wheel cylinders as actuators are lightweight;
3. When towing a trailer, the trailer can use either air brakes or hydraulic brakes.
According to forum truckers' experiences, air-over-oil brakes do have good stopping power and respond quickly, and they won't feel as harsh as pure air brakes, but they also have drawbacks. Long downhill runs with high temperatures can degrade the brake fluid, the seals in the hydraulic wheel cylinders (slave cylinders) can melt or even fall off, causing brake fluid to leak and making it feel like the brakes suddenly lose power (basically, the quality of these rubber seals is definitely a big issue); moreover, constant maintenance and dismantling brake drums is really annoying, and in terms of reliability, they just can't match the relatively simple pure air brakes.
Editor's note: Nowadays, apart from vehicles like loaders and dump trucks that require hydraulic systems, it's hard to find air-over-hydraulic brake systems. Also, a type of clutch booster on trucks is often called air-over-oil, but that's not accurate. The clutch system uses a slave cylinder aided by air pressure, which is a completely different principle from air-over-hydraulic brakes. Next, I will introduce this type of clutch booster pump.
Previous Page
Previous Page
Focus on the research and development of automotive brake systems and pneumatic brake valves to promote the development of the auto parts industry!
Contact Information
Telephone:86-575-87438928
Mobile:8613252110178
QQ：1185450863@qq.com
Address: No. 461, Advanced Village, Fengqiao Town, Zhuji, Zhejiang Province
Online message
Submit your information and we will contact you as soon as possible.