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Steve 12-23-2003 10:04 PM

What kind of brakes does your bus have?
I have good old hydraulic.

lapeer20m 12-23-2003 10:09 PM

gotcha thinking, didn't I???

by the way, i'd like to say THANKS for creating such a wonderful place for us wacky people to gather and share thoughts on everything skoolie. You've done a wonderful job so far.

John Chance 12-31-2003 12:36 AM

Type of Brakes....
My 91 International has 4-wheel hydraulic disc brakes, with a really weird vaccum assist off the Allison tranny. I still do not understand how that rig operates. :?

My 86 Jimmy has air brakes (twin tanks) with the anti-lock mechanism. :)

My 84 Chevy "Shortie" has front disc, rear drum, anti-lock up mechanism, boosted off the power steering pump. :P

RonS 04-22-2004 11:11 PM

Brake choices
I went with air brakes on this bus for safety reasons.

Back in the late '80s I had an old school bus that had a brake line rust through and blow out leaving me with no brakes. It happened that I was just pulling out of our driveway at low speed and nothing bad happened.

I'd rather not go than not stop if there's a brake failure.


abdabbs 07-16-2004 04:25 PM

good ol hsssss..
...air brakes. Gotta love that sound ! :D

David G. 07-19-2004 11:57 PM

my old 74 chevy skoolie has an old vaccume type brakes......that of course dont work very well............WHOOOOOOA.....PLEASE STOP BUS!!!!!!!

gealto 08-18-2004 04:28 PM

Dual Vacume Brakes
OOps, I mis-cast my vote as having pneumatic brakes. Actually, "hydraulic" brakes are vacume actuated, and the force comes from the pressure of the atmosphere, so they are air actuated.

Maybe the categories should have been air versus vacume actuated?

Air brakes are way over-kill for a skoolie. They're ultra expensive to maintain. Somebody ELSE has to work on them for you, while the dual vacume brakes are easy to work on yourself. Also, no special license restrictionsd apply.

A proper skoolie attitude is to not drive very much, to use back roads, and to never drive over 45 mph. Always asume that the brakes are about to fail. A stick shift greatly reduces the need for brakes anyway, so have one of those, and a good mechanical parking brake is good backup.

Heck, mine just sits in the yard all the time anyway, so why does it matter? Mine has been my dream machine. I spend time thinking about it. I planned to retire in it, still at least 15 years away.

lapeer20m 08-19-2004 12:22 AM

I disagree with that post on so many levels! First of all, I actually drive my bus, it doesn't just sit on my property. Iv'e driven about 15 thousand miles in the past year and a half.

Hydrolic brakes are not actuated by atmospheric pressure, I believe almost all of them use vacuum from the intake manifold.

For must of us, if we had to get a brake job done once on our skoolie, those new brake shoes would last longer than our bus. Re-shoeing a bus with air brakes is actually quite simple.

You can't beat the stopping power of air brakes! They are far superior to hydrolic. If they we'ren't better, semi-trucks would all use hydrolic brakes. A kid can press the brake pedal hard enough to lock up all 6 wheels in a bus with air.

It's super easy to adjust air brakes, it takes about 10 minutes total to adjust all four. I do this once every couple months. (I plan to do it a few times on my 5k mile trip across the USA) IF part of your air brake system fails, parts are readily available at any truck repair shop. Air brake parts are nearly identicle for all big trucks/buses.

One huge safety factor with air brakes: If the system ever failes, your bus stops! If your hydrolic brakes fail, better hope you don't need to stop in a hurry.

Who says a skoolie shouldn't go over 45?? I do plan to get to my destination before I die! Most skoolies don't go much over 55 which is a perfectly acceptable speed.

An added bonus is the availability of compressed air for filling tires, or utilizing air tools, and of coarse using those new air horns.

I appologize for being so argumtative, I"m cranky today!

gealto 08-19-2004 11:23 PM

And I disagree with your disagreement! :-)

A vacume is merely the absense of pressure, it isn't a "thing" of itself. There is no such thing as the force of a vacume. It's the air pressure on the outside doing the work, so "vacume assited" brakes is a misnomer, they're really air pressure assisted.

If you want to blast down the interstate all day at high speed, why not get a motorhome? That's what they're designed for. Skoolies, to have any meaning in and of themselves, must be different. They need to take the opposite approach, otherwise its a pointless endeavor. School buses are NOT designed for efficient high speed cruising. They're designed for back road medium speed driving under average conditions. Many don't understand this, get a schoolie, then want rid of it because it's a no good fuel hogging noisey shakey and dangerous high speed cruiser..

Go ahead and spend a few thousands on that old bus only to find later that nobody will buy it from you, 'cause they want a real motorhome.

Air brakes are mandated on trucks due to public safety issues and the irresponsibilities of commercial drivers. If they were so much inherently "better", then they would be on cars, too, right? Wrong, they will never be on cars, don't need all that stopping power. You would probably put air brakes on your moped, cause they're so much better.

Airbrakes unnecessarily raise the maintenance cost of the vehicle. It aint the shoes, it's the cost of fixing problems when they occur, like air leaks and compressors and such.

busone 08-20-2004 01:02 AM

I have to agree with lapeer20m, air is better. Hydraulic is great for small stuff. I have a real problem saying that commercial drivers are what make hydraulic breaks bad for trucks. Commercial drivers are generally much better drivers than the general public that is why they can drive 80,000LBS down the road. I would not want to be in my car in front of a fully loaded cement truck with hydraulic breaks. I wonder why trains use air breaks and not hydraulic?

School buses are designed to drive on all sorts of roads from city streets to back roads. I went to school in one of the largest school districts in the nation and many of the buses had to travel on the highway to get to the schools. The bus I rode spent half of it's time on the freeway getting us to school and we traveled just fine at 65MPH. Whenever we had a sports tournament we always rode in a school bus and usually it was far away and we would be on the freeway.

Jarlaxle 11-27-2004 06:42 PM

My B-700 has vacuum-assist 4-wheel hydraulic drums.

Demonknight 01-18-2005 06:40 PM

after working in a truck stop for a number of years I'm far more confertable with trucks on either side and in front of/behind me than the dorks in the suvs on thier phones...I KNOW the truck drivers know what they are doing..if in doubt go look at a cdl instruction book and compare it to a worthless thing they give a "normal" driver.

TravelingMan 03-05-2005 10:51 PM

Air breaks on on heavy trucks are a good thing. On tractor/trailer or a train think about how much fun it would be to drop a trailer if you had hydrolic breaks?
Think about going down a long steep grade and your hydrolic fluid is so hot that its boiling in the pistons and now you have air in them. No breaks! :shock:

Air breaks are easy to adjust and you have an air gage or two to tell you when may have a problem.
True if you ignore air breaks you can get into serious trouble.
Air leaks,ruptured air line or a weak compressor? Oops get ready to come to a screeching halt. I hope you know how to cage the rear breaks or fix the problem otherwise you wont be going anywhare soon. :P

Air breaks just make good sence on a big heavy truck.

Branden 04-19-2005 01:58 AM

Lucinda has air brakes.

Guess I need to learn how to cage them. Guess I need to learn what that means.



abdabbs 08-10-2005 12:33 AM

air brakes
i do not think i would be comfortable driving all 19700 lbs of ol betsy down the road with hydraulic brakes.

and yes things do go wrong....

im just in the process of swapping out my ol compressor for a remanned one that cost me 350 smackers. and i have an air leak on the exhaust side of the system thatll run about 75 bucks in new hoses but it will definately outlast the bus once its done.

one day when traveling out to mid states ford here in des moines i had some moron in a jeep liberty think he could dart in front of me and immediately put on his signal and brake from 45 to 10 mph in 20 feet or so.... needless to say i found out how easy indeed it is to lock up all six tires... only if i could have seen his wifes face when she smelled his drawers when he got home !!! (i had to check mine also lol).

air brakes all the way !!

seems like a ramble to me...better stop drinking and hit the sack!

TonyC in Iowa

thomastedder 08-14-2005 05:52 PM

Mine has air brakes. Man do I love that sound! CHSSSHHH.

Griff 08-14-2005 06:44 PM

OK, maybe I should have been paying better attention to the poll results before. . .I am aware of hydraulic, pneumatic & electric brakes, but what other types are available!?! Do those "Other" 3 people have Fred Flinstone brakes?

Wolfman 10-30-2005 10:02 PM

Air brakes. Sorry, but IMO, part of the reason for building an R.V. out of a skoolie IS because the rig is so seriously overbuilt. The brakes should be JUST as overbuilt. As for difficulty of working on, they really aren't that different from hydraulic brakes. Just replace the fluid with compressed air. Air brake parts are bigger, and easier to work on. Instead of a master cylinder, I have a proportioning valve under the dash. Air brake lines arerubber and plastic, and therefore much more resisitant to corrosion than the metal hydraulic lines.

Sturgeon1 06-03-2006 01:32 PM

My old girl is a vacuum assist, hydraulic drum type. All brand new parts from the drums out.... What a job!

The Slims 08-14-2006 11:36 AM

If I said my bus was built like a truck I'd be wrong. My bus IS a truck and I'm happy to have some big ol' heavy-duty air brakes on it for stopping power, safety and ease of maintenance. Once I understood everything I was sold.


Excalibrate 03-12-2007 10:04 AM

Air brakes here, had one with hydraulic and was barely adequate once I got it loaded and towed my jeep. Had to make a couple quick stops in the new bus, much better. Some people seem to want to justify their choices by telling everyone else he is right and we are wrong. A skoolie is a personal choice and can be configured in whatever way suites the owner and their needs. It's a freedom thing. Dont f#@k with my freedom man!

the_experience03 07-30-2007 08:53 PM

Re: What kind of brakes does your bus have?
250 hp Cummins? :shock: Do you have a 6CT or ISC (8.3 liter) in 30 passenger bus? Very cool if you do.

Abbott 08-19-2007 01:41 PM

Re: What kind of brakes does your bus have?
As a School Bus Conversion rookie I am finding this thread of great interest. Air-brakes verse hydraulic brakes is something I have been considering myself while researching this subject. I have worked on both types, hydraulics on cars and pick-up trucks, air-brakes on railroad cars. Both are easy to maintain. Hydraulics are well known, air-brakes (for the railroad) would require regularly scheduled COT&S (clean, oil, test and stencil) maintenance. Linkages and shoes would be visually inspected, bearing surfaces (fulcrums) would be cleaned and oiled. One end of the rail car (the B end) would have the airline plugged. The other end of the car (the A end) would be hooked up to an airline that ran through test gauges to bring the air-brake system up to the required specs. (pressure). The test would consist of testing if the cars air system would hold the required pressure (10 minute test). Then the brake system would be actuated and the shoes would be visually inspected for hitting the wheels properly. The linkages would or would not be adjusted and then the emergency system would be tested by simulating a complete air dump. When the car's air system received the proper inspection, maintenance and testing the test date was then painted (stenciled) on the car.

If something in the air brakes system didn't meet the Federal requirements then it would be adjusted or replaced to within tolerances for linkages and shoes. Air valves would require replacement of sections/parts of the valves and so forth. This consisted of loosening a few bolts and/or nuts, replacing a few O-rings and/or valve parts. The replaced valve parts would be sent back to the factory for rebuilding. The linkages and shoes would be replaced with new or used (again depending on Federal requirements) then be sent out for recycling. All in all the air-brakes were easy to maintain and repair once the system becomes well know by the mechanic, in the case of Skoolies, that mechanic may well be the owner/operator.

DizzyIzzy 10-12-2007 11:45 AM

Re: What kind of brakes does your bus have?
I have hydraulic brakes. I like them because I know how to work on them. I find it is best to know what your in for. Now by the time I replace this bus I might think of Air, But for now I like hydraulic. And I don't plan on a another bus for at least 5 years.

hoser 10-12-2007 09:09 PM

Re: What kind of brakes does your bus have?
Air Brakes

87 Bluebird Chevy C60 chassis

Jarlaxle 10-14-2007 01:08 PM

Re: What kind of brakes does your bus have?
Uh-oh. This is not good. I have bad news...I think you have the dreaded Lucas-Gierling brake system. Do you have a pull knob (like air brakes) for parking? Do you have a hydroboost or electric booter at the master cylinder?

Get a L-G brake manual, and MEMORIZE it. Any shop charges an arm, a leg, and your nuts to service these brakes.

the_experience03 10-16-2007 05:35 PM

Re: What kind of brakes does your bus have?
That sure sounds like every L-G brake system I've heard of. I don't know why Ford insisted on using it so much. In theory it's a great system, but in practice it proved to have its issues. Don't let that turn you off at all. Just be aware that the system is a little less common and make sure you understand how it works. Also, check that big main pipe that carried fluid back to the chambers to back off the parking brake and sure it isn't corroded. Everything I've read points to that as the most common failure point bringing you to a rather abrupt halt.

the_experience03 10-16-2007 11:27 PM

Re: What kind of brakes does your bus have?
The ones I have heard of having problems are the ones that actually use a large steel pipe to plumb the pressure back. I have never heard of a rubber version, but that most CERTAINLY doesn't mean it exists. If it is in fact a rubber line you might just be lucky enough not to have problems as I believe this is the retrofit most people go with....30 feet of hydraulic hose to replace the pipe.

BBTC2K 10-21-2007 09:22 PM

Re: What kind of brakes does your bus have?
Mine has good old air brakes...drum and "S" cams. Simple to change those out...The key is to REALLY lube up the rollers and the roll points. We use anti-sieze at the garage. works wonders. Changing out the rear air chambers can be deadly if you arent careful, but it is a relatively fast job. My bus uses nylon line just about everywhere. easy to repair those too. I may have learned a little too much about them... Mine has automaic slack adjusters on it so I don't have to crawl under it except to check the lining, and our company always removes the backing plates to allow for better cooling, so its a snap to check them


Caibel23 01-15-2008 08:32 PM

Re: What kind of brakes does your bus have?
Which pedal is the break?

My new bus is hydrolic, my old bus is air, I have hauled 1 ton of water with air breaks, is there anyone that thinks 1 ton of water would not be so wise with conventional hydrolc breaks?

the_experience03 01-15-2008 09:33 PM

Re: What kind of brakes does your bus have?
1 ton of water is nothing. You have a bigger hydraboost brake system than your everyday 1 ton truck and they can currently handle a payload in the neighborhood of well over 4000 lbs. As long as you aren't exceeding the GVWR of the bus I don't think it will be an issue safety-wise.

Now as far as legality I'm not sure. With water you're probably ok, but make sure there isn't a restriction on unbaffled tanks or on the total number of gallons you can haul without a CDL with tank endorsement. I think you should be just fine at about 250 gallons.

IsolationRide 03-17-2008 05:11 AM

Re: What kind of brakes does your bus have?
Hydraulics. And after reading someones post in this thread. New parts and brake lines for my baby ! WHOAAA BUS !!!! Good Girl.

lapeer20m 06-24-2008 09:53 AM

Re: What kind of brakes does your bus have?
I had 2 buses in my driveway that had diesel engines, gvw over 28K, and hydraulic brakes. Phill's bus also is diesel, big, perhaps 81 passenger, and has hydraulic brakes.

There is a good backup braking system on these buses. it's a 12 volt hydraulic assist mechanism.

I've also had a couple of buses that have air brakes and have similiar gvw's to the other buses.

so weight doesn't seem to play much of a's more a matter of what the school district prefers when they order their buses.

the_experience03 06-24-2008 10:07 AM

Re: What kind of brakes does your bus have?
Here in the north country buses operate almost exclusively with hydraulic brakes. Replacing rusted out hydraulic lines seems to be preferable to dealing with frozen brake components. -20 F is not an uncommonly low temperature in this neck of the woods during morning pickups and the buses need to be reliable at that temperature.

Anyone have any idea what the cost difference is between the two systems?

Navistate 12-01-2008 11:25 PM

Re: What kind of brakes does your bus have?
My 1959 Superior with International chassis has Hydrovac brakes. I feel I should upgrade but they can sit for years and always work.

lapeer20m 12-02-2008 10:24 AM

Re: What kind of brakes does your bus have?
only slightly off topic.....

i just started a new job as a professional firefighter/paramedic. I was very intrigued by the braking systems on our ambulances. They are similiar to this one here:

basically a bus chassis, just a little shorter and for a different purpose.

anyhow, the brake system is new to me. It has air ride suspension, and a regular engine driven compressor, and you set the parking brake with the familiar air brake knob you hear "whoosh* when you set the parking brake. Now for the strange part......When you turn the key on and the engine is off, i can hear the familiar sound of an electric over hydraulic backup brake booster. hmmmmm. After researching, i found that the ambulance has hydraulic disk brakes.

so, it has

air ride suspension

air parking brakes

hydraulic primary brakes, with abs


i'd love to buy one when they are taken out of service. These cummins 5.9 engines and 6 speed electronic transmissions rock! They do 85 or 90 mph right now!

the_experience03 12-02-2008 08:33 PM

Re: What kind of brakes does your bus have?
Does it have air over hydraulic? That's actually a fairly common setup. I suppose they could be air screw style discs, but you wouldn't have a master cylinder then so you would know. Neither option really explains the backup motor noise though I don't think.

Jarlaxle 12-04-2008 06:47 PM

Re: What kind of brakes does your bus have?
They're a common MDT and shuttle bus setup, air-assist hydraulic. The shuttle company I worked for had five buses (three IH 3800's with T444E/AT545's, one Freightliner FB65 with 5.9 Cummins/Allison 1000, one GMC C5500 with 6.6 Duramax/A1000) with that setup.

dieselman69 01-21-2009 06:55 PM

Re: What kind of brakes does your bus have?
air brakes on mine like them very much so far :lol: :lol: :lol: :lol: :lol:

busdriver_phil 01-13-2010 07:11 PM

Re: What kind of brakes does your bus have?
I'm jealous of your Jake. I briefly owned a 72 Crown tandem-axle, Detroit 671/5sp stick, for historic preservation purposes. Sold it to a friend who was in a better position to restore it. I'd love to get one for the Skoolie project but my bus nut friends would kill me if I ever chopped up a Crown to make an RV. They're a page out of history, and I think us bus nuts should preserve as many as possible. On the other hand, they're lots of fun to drive, and I'd rather see one enjoyed in its second life as a nice camper than go to the scrapyard.

As for brakes, I think any bus longer than 6 rows should have air. Air brakes are more powerful, and have the spring-applied failsafe that will stop the bus in most brake failure situations. Medium-duty vehicles (buses, straight trucks) can be ordered with either air or hydraulic. Heavy-duty vehicles (tractor trailers, larger straight trucks, and don't forget trains) always have air - that tells me something.

I had a brake line blow out on a hydraulic school bus - I was able to stop using the other half of the dual system, but it was pretty scary feeling the pedal go to the floor. The parking brake is designed to stop the bus in an emergency, but I've seen those cables snap when applied for normal parking and let go while buses were parked. In normal use, the adjustable handle (twist the knob at the end of the lever to increase or decrease pressure) tends to loosen up, and some brakes may be "applied" with less than enough force. Most parking brakes are mounted on the driveshaft, and any driveshaft or rear axle failure could render the parking brake useless.

If you blow an air line, you can pull the park knob for a full rear brake application. It won't be the smoothest stop, but unless you're on snow or ice it won't lock the wheels. If anything breaks on the system, aside from a failure of the rear brake components, the parking brake will keep the bus from moving until you get enough air in the system.

For the record, school buses are offered in nearly every size with either hydraulic or air brakes. Gas engines usually had hydrovac. Air was an option on gas buses, but rare. Ford buses ordered with hydraulic from the 80s-90s nearly always had the Lucas-Girling system. Some heavy-duty transit-type buses are only available with air, but I've seen models up to 40 ft (84 capacity) with hydraulic. Internationals from the late 90s and early 2000s could be ordered with hydraulic service brakes but an air parking brake - this was driveshaft-mounted but spring-applied and air-released (other manufacturers also offer this system in buses and trucks). Since 05, International has used a power hydraulic brake system (in lieu of the optional air brakes) which includes a spring-applied electric-hydraulic driveshaft parking brake, and gives the pedal more of an air brake type feel.

Will 06-19-2010 10:59 PM

Re: What kind of brakes does your bus have?
I drove 66,000# GVW trucks pulling howitzers in the marines. The old M813 5-ton 6x6 had air over hydraulics and the M923 6x6 5-ton had full air. The M198 howitzer had air/hydraulic. They both had the same 14-liter, nastily ass-pirated 250hp Cummins. The 813 was a 5-speed manual and the 923 was a 5-speed Allison auto. Driving it, the 813 had more power because the torque converter on the 923 was sucking it up. The 923 was better because the cab was a lot wider inside. In neither case did the brakes make a bit of difference. The hydraulics were just as good as the air.

The main issue that is being disregarded here is the benefit of a disc over a drum. A drum is an oven. A schoolbus doesn't have an exhaust brake, generally, and drum brakes are heat ovens. Once the brakes get hot, that's it. You can have lots of pedal pressure, but it isn't slowing you down.

I don't think drum brakes are allowed on heavy-duty trucks in Europe anymore because their stopping distance is much less than discs. Whatever applies pressure to the shoe or pad doesn't matter. It's a matter of convenience. A diesel makes no vacuum so you need a pump. A gasser makes vacuum and a resevoir is cheaper than a pump. The steering pump (hydra-boost) or an electric pump (my bus) can be used to boost hydraulic pressure. The real issue is disc or drum and disc is the clear winner.

XE1UFO 07-20-2010 09:25 PM

Re: What kind of brakes does your bus have?

Originally Posted by CHEESE_WAGON
My personal observation has been that gas-powered buses typically will not have air brakes, and I have never seen a diesel model with hydraulic brakes.

Mine is a Ford B700, with a 28-passenger Thomas body, 5.9L Cummins diesel and 5-speed standard tranny. Yes, it has HYDRAULIC brakes.

npeace 12-14-2010 08:59 PM

Re: What kind of brakes does your bus have?
Air brakes. And I'm surprised no one has mentioned an obvious advantage to air brakes - no nasty brake fluid to deal with and no bleeding of the system. Most of the parts to the sysem are pretty much universal and widely available, and there are no steel lines to bend and rust out. I don't know why some people are scared of air brakes. That doesn't mean you should hop in a bus with air brakes and head across the mountains with no knowlege of the system at all. They are not quite as idiot-friendly as hydraulic brakes, but they are certainly safer and better.

gseufzer 02-18-2011 07:24 PM

Re: What kind of brakes does your bus have?
I have 4 wheel anti-lock Air brakes, and very glad to have them. Air brakes are a fail "safe" system, loose hydraulic pressure, no brakes, loose air pressure your going to stop like it or not. the down side would be the maintenance cost buit i think its a small price to pay to be that much safer. G

gseufzer 02-19-2011 06:56 AM

Re: What kind of brakes does your bus have?
a good place to look for that crash course is on you tube, look for school bus brakes, I found a bunch of training videos on there that were very good

syke 04-12-2011 01:37 PM

Re: What kind of brakes does your bus have?
Our bus is equipped with air brakes.

Kman 08-18-2011 08:37 PM

Re: What kind of brakes does your bus have?
We haven't bought our bus yet, but it will be an air brake bus. I have driven many trucks with both air and hydrualic brakes. I have driven cranes, log trucks, aerial lift trucks and fuel trucks with air brakes, I have also driven log trucks, aerial lift, and chip trucks with juice brakes and currently still own a Ford F600 with Lucas-Gerling brakes(I will NEVER buy another). I have no problem working on air brakes and we want the on board air to run air tools for working on the bus and our Jeeps while on the road.

Accordion 01-17-2012 10:14 AM

Re: What kind of brakes does your bus have?
Air brakes on my bus. I had to do an emergency quick stop once and was impressed with the stopping ability of the air brakes. I also like the safety feature of the rear brakes locking on if you lose air pressure, although I would never want to be in that situation.

I was impressed that my bus stopped so quickly without screeching the tires.

PDBreske 01-19-2012 01:13 PM

Re: What kind of brakes does your bus have?
Four-wheel hydraulic disks with boost supplied by the power steering system on my bookmobile. It stops well.

As someone else mentioned, the main reason any truck that pulls a trailer with brakes and all trains have air brakes is because there is no other way to get the braking system connected from vehicle to vehicle. When a trucker backs up to a load, he just connects the air lines and the system fills the trailer brakes with pressurized air. Done. That would be ridiculously time consuming with hydraulic lines.

Looking at the poll results for this thread, it appears the air brakes reside in about fifteen percent more buses than do hydraulics. It's probably due more to the whims of school districts than the perceived benefits of one system over the other.

If air brakes were so vastly superior to hydraulic brakes, you know very well that someone would have sued all the major car manufacturers for subjecting millions of drivers to an unsafe and inferior system. And the government would have mandated their installation in all cars.

chev49 01-19-2012 02:06 PM

Re: What kind of brakes does your bus have?
there are other systems besides air and hydraulic with vacuum over. For example, i recently had one truck that had vacuum over hydraulic trailer. In the late 1930's magazine that i have, they used vacuum that pulled the mechanical rod for the mechanical brakes on a trailer.. and the article on how to build it.
Vacuum requires quick disconnects as well as air.

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