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Air Brakes on pickup trucks
11-17-2006, 03:07 AM
Post: #1
 
First off, I'll admit I know nothing about how air brakes technically work. Would they be a bad option for pickups though running big tires? Can anyone chime in here with something positive to ad?
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11-17-2006, 02:27 PM
Post: #2
 
im not sure but i would think it would be a hell of a lot of work. depends if ur gonna be doing heavy towing only on highways you might be ok. but i wouldnt rely on just air brakes. you would also pri want an engine or exhaust brake also if u were going to do this. in a stop and go type driving it wouldnt be realalistic. u also have to remember that airbrakes are much more touchy. i dont think in a pickup it would be practicly. if your looking for a heavy break buy a bigger pad a rotar. tha will help ya. youll pri have to run a bigger wheel thou.
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11-17-2006, 02:35 PM
Post: #3
 
Quote:On 2006-11-17 02:07, blasphemous wrote:
First off, I'll admit I know nothing about how air brakes technically work. Would they be a bad option for pickups though running big tires? Can anyone chime in here with something positive to ad?

you know big rigs still use huge a$$ drum brakes right?




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11-17-2006, 02:37 PM
Post: #4
 
can you do that?? how do air breaks work anyway? sorry...newbie question.
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11-17-2006, 02:44 PM
Post: #5
 
Air brakes run on the same principle as conventional hydraulic brakes. Instead of a hydraulic cylinder applying the force to push the brake shoes out against the brake drum, a pneumatic cylinder does.

That being said, I don't think it's possible, as I've never (myself) seen or heard of a pneumatic brake caliper. As Black Sheep, I think it was, indicated, all large trucks run drums at each wheel.

Further, air brakes wouldn't really be any more effective than hydraulic brakes, even if you could, simply, replace the hydraulic system with a pneumatic system. After all, a give sized caliper/wheel cylinder, given sized pad or shoe, and a given sized rotor or drum is only capable of so much braking ability, regardless of whether it's hydraulic power or air power applying the force. When the pad/shoe/rotor/drum reaches its temperature threshhold, that's it. Period. It's not like pneumatic power is going to make a vehicle stop any faster because it's, simply, pneumatic powered. When pads & rotors (or shoes & drums) get hot, they're hot.




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11-17-2006, 02:50 PM
Post: #6
 
I could be wrong, so correct me if I am.
anyway, from what little I've seen of air breaks, they are basically just a big drum break(as mentioned above) but instead of being actuated by fluid like the breaks on a regular truck, they are actuated by an air cylinder.

they might be ok if you were never going to go off road, but i'd imagine that the air cylnders would get beat up pretty badly if you were to take it off road.

there is a picture at the top of this page, http://www.e-z.net/~ts/ts/brakpg.htm

you can kinda see how the air chamber sits quite a distance from the back of the drum, and would be an easy target for getting bashed wile off road.




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11-17-2006, 03:00 PM
Post: #7
 
I thought big rigs still used drum brakes because they can get more braking surface from big a$$ drums?

Good points on it's vulnerability and practicality. Thanks for chiming in guys!
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11-17-2006, 03:04 PM
Post: #8
 
And just, for the heck of it/sake of it, to throw this out there:

Air brakes, such as those on transfer trucks, or "tractor trailers" as some folks call them, operate in the condition that if the engine isn't running, or there's no pressurized air in the system, the brakes are "locked up," per se. What I mean is that, in a big truck, for example, when it's sitting there, parked, and not running, the brake shoes are "applied" to the drums...i.e. like having the parking brake applied, except when you apply your parking brake in your pickup truck or passenger vehicle, the only wheels that have the parking brakes applied is the rear wheels. In a transfer truck, ALL of the brakes are applied when there's no air in the system.

When the rig is fired up, the compressor is driven by an engine-driven belt, just like the alternator and such. The engine and, therefore, compressor have to run for a while until there's sufficient air in the braking system for the brakes to "release." So, in all actuality, a hydraulic system works in the opposite direction of a conventional hydraulic braking system. A conventional hydraulic system is applying no pressure until you direct it to apply pressure, via the brake pedal. In a pneumatic/air braking system, the brakes don't apply pressure until you hit the brake pedal which, in fact, RELEASES air pressure.

So, keep that in mind the next time you see a movie and a big rig is sitting there, shut off, and all the sudden it starts rolling down hill or the driver hits the brakes and the truck won't stop. Pressurized air is what keeps the brakes from NOT applying. If the truck lost air pressure...the brakes would apply and/or lock up.




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11-17-2006, 03:16 PM
Post: #9
 
ZacD
Somehow I knew that, it just didn't come to mind. A big spring inside that cylinder is what actually applies the braking force isn't it? I think I seen it on Trucks on the PowerBlock some time.
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11-17-2006, 03:52 PM
Post: #10
 
yes, brake pressure is always applied by a spring. I have been into the brakes on our freightliner before, and there is o way i would retrofit that crap to a pickup.

as zac said, they work the opposite of what you would think, the air actually pulls the brakes away from the drums.

also, the reasons for air over hydraulic in a big truck are:
1.Safety while parked or in case of brake failure, as mentioned, with no air pressure, it won't move

2.Heat. As mentioned, the contact surfaces will still over heat, but there is no brake fluid to biol and loose pressure

3.Sheer size. It would take very large lines, master cylinders and wheel cylinders to operate as well as a very good booster for the master cyl. Why do you think larger trucks use hydra boost brakes? It take s a lot of pedal pressure to move all that fluid and those large cylinders.




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