I drive big trucks in the course of my work and most of them have air brakes, they have 4 wheel drum air brakes. Some of the trucks have 4 wheel disc hydraulic brakes and they take more effort and distance to stop than the air brake equipped vehicle. Now I know that despite what many believe, that the big part of why the air brake equipped trucks stop better is because they have drum brakes which have more surface area than disc brakes and more friction area= better brakes.
Why do cars only have hydraulic brakes? Wouldn’t they stop quicker with air brakes? Most cars have 4 wheel disc brakes despite being problematic and prone to warping, and they have reached maximum performance in regards to stopping distance, so isn’t air brakes the next logical improvement?
Here are some benefits to air brakes.
-No fluid to house or cool, simplified brake maintenance
-If you get air brakes too hot (or any brakes for that matter) they will “fade” and your vehicle will no longer stop. Air brakes are not fade proof, BUT can dissipate heat a lot better than hydraulic brakes
-You can use drums and still have better stopping distance than disc brakes without the warping pulsating discs.
-Disadvantage: Air compressor (bigger load on engine) bigger possibility to freeze up on you (winter time + humidity), but I have never had air brakes freeze on me.
-People say the pedal feel is poor, but alot of hydraulic brakes have poor pedal feel.
The advantage of air brakes is quite simple. Air brakes are a proven technology that will apply more pressure that hydraulic brakes and will stop a heavy vehicle far quicker with a foolproof system. One leak in hydraulics and it’s game over. Air brakes are almost foolproof. The parking brakes are kept off by air pressure. Lose air and the brakes slam on. Apply the foot valve (pedal_ and air will apply the wheel brakes like nothing hydraulic can do. Love 'em. Millions of semi’s can’t be wrong