Air Brakes vs Hydraulic?

[Seeria]

Thinking of picking up an old bus (86) that has air brakes and must say I find the idea of air brakes creepy. Reading over DMV manuals they seem to be a huge pain in the butt, constant mainenance, checking, expense, etc. I see why they need a special license.

So why bother? Why go air over hydraulics?

[Wis Bang 2]

Medium size vehicles use a form of power brakes called 'hydrovac' but still depend on the brake fluid to actuate the individual foundation brakes. Air brakes don't require a fluid connection and provide a more consistent application as the air pressure stays more constant than the systems using engine [manifold] vacuum. Air is also quicker than fluid pressure transfer.

The engine drops to idle changing the amount of vacuum available VRS the amount of compressed air in the tank. Stalling the engine completely removes the source of vacuum while the air tank should supply several brake applications before depleting the air supply.

Gladhand connections allow the foundation brake system to be extended to a trailer instead of having to add a electric controller for the trailer brakes.

Airbrakes will operate larger brakes, and more of them, than a hydraulic system. That's why you don't see 'Big Rigs' w/ hydraulic brakes.

Finally, the harder you press on the foot valve, the harder the brakes shoes push against the drums.

Don't be afraid of air brakes, DO get some education about them. That year bus should be required to have automatic slack adjusters making the maintenance much easier. It should also have a moisture elimination device to diminish freeze ups in cold weather...You will still have the ability to stop when you develop a small air leak, not so w/ hydraulics...

[taylorlambert]

I buy all my trucks wit hair brakes. My old favorite dump truck is parked now waiting till I can get the hydra boost fixed. Gonna be about 1200 in the long run. Another good point on the air brakes is if you get a leak or loose a brake line your double lockdown on the pull axle will begin to lock down then when the air is below a certain level it will fully apply. One job I was hauling with my old hydraulic brake truck I was sitting in on a slop being loaded and a pinhole came in the line. Had to cancel the job to take out a section in my brake lines. With air brakes and plastic lines you can cut them and usually pull some slack out and replice with a liner and ferrule kit.

[Sawmill Jim]

Air is the best way to go for sure . In case of an air leak the warning buzzer should sound you may have time to park before they lock down .

[Beeman]

I don't know what the outdated DOT manual had that made you think air brakes are a problem. It's a very simple dependable efficient braking system. Most every truck on the road today has air brakes. One good thing right off is that if you have a leak you get a warning and the vehicle stops. With hydraulics you get little or no warning and the vehicle will not stop.

[backwoodsman7]

Originally Posted by Seeria

So why bother? Why go air over hydraulics?

I've spent some time driving trucks around 30,000 gross weight, some with hydraulic and some with air brakes. My experience is quite limited compared to some others here, but maybe it can still be helpful. When loaded, the air brakes would stop on a dime. The hydraulic brakes, on the other hand, were not nearly as effective when loaded. You'd stand on the brake pedal, and eventually come to a nice, gentle stop. Of course, you're probably not going to be real close to that weight in a bus, so I'd expect decent performance from hydraulic brakes.

Originally Posted by taylorlambert

I buy all my trucks wit hair brakes.

Hair brakes... I'll have to check into those..

[Seeria]

Thanks everyone! Buses I'm looking at are the small type so not real sure if it is worth paying more for air brakes.

[Ross]

I'm wondering if Mr Lambert is from Que or maybe the Nation?

[mightybooboo]

Those used schoolies can be very good deals,good luck!

[taylorlambert]

Sorry about about the typo, Hair brakes are what I had when running past my older brother get grabbbed by the hair and ya stop as fast as air brakes lol.

[Txrider]

Originally Posted by Seeria

Thanks everyone! Buses I'm looking at are the small type so not real sure if it is worth paying more for air brakes.

Nothing wrong with either air or hydraulic brakes.

You still need to maintain either kind, and one isn't more of a pain than the other really. People have commented on some of the differences.

The big difference for me is pressure. Air brakes can never apply more pressure to brake than the air pressure you have. Hydraulic brakes you can apply as much pressure as you can physically apply, even with a vacuum assist power unit.

So with air brakes once you are applying your max air pressure, pushing harder on the pedal accomplishes nothing at all.

In my experience air brakes just need to be adjusted regularly and they are fine.