Hydraulic-over-air relay valves are designed to convert hydraulic-modulated input pressure to a proportional output air pressure. The valves are suited for on and off-highway applications, including ...

It’s impossible to fix something without understanding how it’s supposed to work. Brake system repair decisions can be difficult to make, and costly to execute, without a basic understanding of system ...

Descending a long downgrade can trigger a runaway even when your brake system is in good working order. Here’s why. The treadle valve, under the pedal, sends only a small air signal. It activates a ...

Many of the larger vehicles on our roads have one intriguing thing in common: They can make sudden, loud, gas-escaping hissing noises. These noises, admittedly, have made this writer jump — on more ...