The Stovebolt Site Forums The Parking Lot Big Bolts air disc brakes, input wanted

I have been looking at some air operated disc brakes. Right now it looks like Haldex has the best ones, but I can't find much about them, and how people like them.

Here is a brochure on them http://www.hbsna.com/Documents/broc...0Air%20Disc%20Brakes%20L20440%203-05.pdf

I know air operated disc brakes were tried several years ago with out very good results. Seems they have better results this time around.

I am considering them for my 48 6400.
According to Haldex, they make them to fit under 17.5, 19.5, and 22.5 wheels. My current hydraulic disc brakes fit in 19.5 wheels, and the wheels I will run are 22.5, so they should fit my truck.

Still trying to find out if they already make caliper brackets for my axles, a 94 Chevy 3500HD front and 88 P30 rear. If not, then I think I can make my own.

Also trying to find out more on how they work. Looks like they have single acting brakes, as in loose air pressure and you have no brakes. I have seen some of the old disc brakes have spring brake cans, not sure if they are available for the new ones.


What do you think, good idea, or bad?
Grigg

Man, what are you going to haul on this 'lil ole 2 ton Grigg? LOL. Are you making a heavy hauler or just doing it for the experience? I personally would stay with boosted hydraulic disc brakes just for servicability and parts availability. But that's just me.
Good luck which ever way you go,
Scott

Not sure what I will haul, but don't want to limit myself unnecessarily.
Both brake systems are comparable as far as stopping power, and the same rotors would be used. I already have plenty of air on the truck for my air starter, so an air brake system would be no more complicated than the hydraulc disc.

The air disc brakes would be great for the ford I have with the Detroit, and I am pretty sure the axles I have under it can be speced with air disc, for sure the front.

For now I think I will keep my hydraulic brakes. But I am interested in the air disc brakes, and I think they could be easier to work on and more dependable. For my truck, within reason, I want the simplest, best, and most reliable components.

Recently I worked on a friend's IH truck with hydraulic brakes, two wheel cylinders per wheel, not much fun. The more I deal with hydraulic brakes the more I think air is the best answer for a truck.

There are 3 major air disc brake manufactures right now:

Bendix-Dana-Spicer-Eaton-Roadranger
http://www.roadranger.com/Roadranger/productssolutions/brakes/airdiscbrakes/index.htm

Haldex
http://www.hbsna.com/en/Products/Air_Disc/

ArvinMeritor
http://www.meritorhvs.com/Product_CVS.aspx?product_id=40&top_nav_str=hvs##SP138

companies hauling tankers seem to be the ones leading the way on air disc brakes as wieght is critical and airdisc system is lighter. I would think there hass to be some type of back up to automatically apply the brakes in event of loss or low air situation. If you have a fuel depot or large tank fleet nearby you might try to go by and talk to drivers or fleet maintence guys. Failing that go to leehi truckstop rt 11, white's or the wilco on exit 205. wilco might be your best bet they go thru a lot of fuel and proably have several fuel drops a day and they have a dedicated fleet of trucks so you could proably catch a driver there.

I have a question for you all.

Does anyone make a complete air brake conversion kit for a specific truck or do you just buy the parts and convert it over yourself.

It will all depend on the axles you have, and if they will accept the brake components you want.

Most big truck axles have pretty standardized wheel ends, so you have a few different brake choices for any given axle. Don't expect this to be true for old stuff.

I think the answer to your question is you just buy the individual components you need, and there are no application specific kits already assembled for you.

When you say air brake conversion, what are you converting from? If it is hydraulic to air there are lots of parts needed, including an air compressor. You may be better off buying a junk truck like yours but with air brakes and swapping all the stuff, be sure it has the same model axles first.

Grigg

Interesting. Another issue that 'converting' may bring up is lisencing the truck. Trucks w/ a GVWR under 26K (I think it's 26) do not require a CDL to drive. BUT, if it has air brakes, you need one regardless of GWR.

I'll have to look into this air disc brakes. I have an older KW K100 that was "suppose" to be factory made with NO front brakes.

Yes, here in VA anything with air brakes needs a CDL. So, theoretically if you put air brakes on your minivan you need a CDL to drive it.

I am not concerned about that part of it. I would probably play dumb to start with, and if it ever caught up to me I would get my CDL if I did not already have it by then.

There were a number of big trucks built with no front brakes from the factory. I don't know how late that was allowed, but I am thinking in to the 60's or a little later.
I have a 25 Mack AC with no front brakes, and a 28 Chevy car, the first year for front brakes on a Chevy car.

Grigg

Grigg,

I have heard that many times too, about needing a CDL with air brakes.

But one day I wanted to find out for sure. I called VA DMV and the woman there told me that as long as the truck has 26,000 lbs or under, she didn't care what kind of brakes it had.

I have never called DMV back to double check her statement, but just wondering if that is a rumor that has stuck around here in Virginia. She may just be right, we really may not need one.

I looked in to getting my CDL a few years ago, even went to the DMV to get the manual to study. I distinctly recall needing a CDL for air brakes, any weight.
There are some loop holes for farm use, but for general purposes I am pretty sure air brakes require CDL.

On another note, I have been told by many antique big truck owners that say even with air brakes, as long as they have antique tags they don't need a CDL.

Grigg

Dang it!

I figured out a loop hole! Don't know why I didn't think of it.....

Tell them it's your RV trailer tower! Heck, those BIG bus RV's have air brakes and those folks don't need a CDL. (I have mine, and yes, some states allow a non CDL driver for air brakes when the vehicle is in FARM use.)

in Canada, well BC anyway, 'an air brake endorsement' on a regular license will do it, tho' that means taking the full course on air brakes, classromm and practice, and ya better not get caught drivin an air brake equipped RV without it

Bill

I keep thinking I want a CDL. But its because I want to pull a heavy trailer weighting 10,000+ and I understand you need one to do that.

Why do they want you to have an air brake endorsement?. When I was a truck mechanic many years ago I'd frequently drive trucks with air brakes and I just don't remember it being that big a deal.

Isn't one of the good reasons for running air brakes the way they are designed so loosing line pressure applies the brakes? I didn't know there were air brakes that used air to apply instead of to hold off.

I knew I wasn't keeping up with the big truck stuff, but now I realize I'm further out of date than I imagined... But then I recently saw a restored truck at a show that was new back when I was a truck mechanic!

Guess I'll just stick with the old stuff.

OldSub has a good point. What is the big deal about air brakes. I started driving big trucks for a company when I was 18. This was way before the CDL days. I found that trucks with air brakes were easier to operate and no one taught us nothing about them. I just jumped in and drove. By the way, these were GMC trucks.

Now if you want to talk about something dangerous, we had some International 1600's and 1800's with Vacuum Assisted Hydraulic Brakes. Those things took some time to get used to. They were super powerful and very touchy. I hated them. Couldn't wait till I jumped back into a good 'ol GMC with air brakes.

(The politicians made it all about "safety". Something about special training needed and such... at least that's what I hear. It pre-dates me by a lot.)

on a tandem axle tractor you could legally order no steer axle brakes until the mid eighties. after that brakes are required on all 3 axles. single axle tractors were required to have steer axle brakes those sometimes came with a limiting switch which would hold the pressure to a maximum 10 lbs to front brakes in slippery conditions. not sure when they outlawed that switch

did you find any one actually using air disc? I don't recall noticing any on the road. talked to some other drivers they had seen a few but hadn't heard anything good or ill other than promotions. lighter wieght less fade under heavy braking.

No, I have not found anyone who has first hand knowledge of air disc brakes yet.
Grigg

The reason air brakes became a big deal in terms of licensing is that they were killing too many people. The foot pedal in an air brake system is simply a valve. The further you push it the more air pressure it directs to the air chambers. It doesn't care if the brakes are out of adjustment and the chamber has bottomed out without applying any pressure on the shoes. To the operator the foot pedal feels exactly the same whether the brakes are adjusted right up or slacked right off. In a juice brake system the fluid is a "liquid rod" connecting the operators foot to the brakes shoes. If even just one of the brakes is out of adjustment the operater is aware of this because the pedal travel is extreme, or at the floor.
Next time you're traveling in the mountains in BC stop at one of the "Brake Check" areas at the top of a steep hill and read the instruction board. It will tell you that if you're vehicle has air brakes check and make sure they're all adjusted up. If you have hydraulic brakes, check for leaks.
Absolutely nothing wrong with a properly functioning juice brake system. The primary reason for going to air brakes is the tolerance for medium loss. Imagine having to connect hydraulic brakes to a trailer. Having to bleed the air out and ensure no leakage at all.Small amount of air loss at trailer connections is insignificant. Air brakes come with their own problems too. Condensation/moisture freezing them up, more moving parts (compressor) to worry about and far more valves and switches than a juice system.
IMHO the only reason to go to air would be if you were planning on hauling a trailer with air brakes or running an air over hydraulic trailer brake system.
Steve g.

I agree with everything you have stated, but just want to add that many straight trucks have air brakes. Many of those trucks had no trailer hitch or any kind of connectors for lines. My opinion is that air brakes is a much stronger and heavier brake system that can also handle stopping a heavier load better related to what you have mentioned about the variable amount of pressure that can be applied.

Driving a truck with air brakes was just an impressive way to stop compared to some of the big trucks we had with hydraulic brakes. Plus back in the old days, before the double master cylinder reservoirs, once you had a leak you had no brakes pretty quick. With air you have a warning system to let you know you had a problem. Then later on, we got trucks with "Maxi" brakes which I believe was one of the greatest inventions man ever made.

i disagreewith steve's statement the pedal feels the same regardless of adjustment. if your brakes are out of adjustment on more than one axle you know it as soon as you hit the pedal. on a normal stop you will use 20lbs or less pedal pressure in an air brake system. if your brakes are out of tolerence you will use more pressure to make even a moderate stop. if some idiot cuts you off there's never enough airpressure regardless of how well adjusted your brakes are. if you are considering replacing standard slack adjusters with automatic slack adjusters you still have to check them fairly often as they don't always work. agree with c10 bill maxi brakes good idea. older trailers the brakes would come on with loss of air pressure but when air pressure was completly gone they would release again so you could pull the trailer again with no brakes. not sure how that worked with the tractors as all those i got where equipped with maxi brakes. which brings us back to griggs original post. if the air disc he is looking at are single action how do they apply the parking brake?

kb3csw
You might have misunderstood my post. I was referring to the actual "feel" of the pedal. Ie, how far it travelled and how much foot pressure it took to apply. Your referring to the "feel" of the rate of decelleration and the operators ability to interpret gauge readings. That is exactly why air brake licensing became a big deal. Too many people were jumping behind the wheel without the ability to interpret gauge readings and mistakenly assumed that, just like in their juice brake car, as long as the pedal felt normal everything was okay. This might be the first time they drive that vehicle and don't know what it's normal stopping "feel" is. That's why the "pre-trip" adjustment checks. Those are precisely the things they teach in the air brake endorsement courses here in Canada.
Juice brake systems are pressure tested on passenger cars at over 2100 psi, compared to probably 200 for air. You can get far more stopping power from hydraulic than from air. The issue became the amount of pedal travel. It's all about ratios of piston sizes. Think about your hydraulic jack. One pump of the handle on your 2 ton jack might move the ram 1/2 inch. The same stroke on your 8 ton jack only moves it 1/8th of an inch, but with a lot more power behind it. Having said that though, single axle trucks up to 5 ton can still have an acceptable amount of pedal travel, but even fully adjusted you will never find the pedal right at the top like you do on a car. Add another axle with more fluid requirements and the amount of pedal travel starts to become marginal.
Back to the original question though, disc vs drum. It doesn't matter what I think, but here's a couple of things to think about. Disc brakes claim to fame is based on 2 things, the superior ability to dissipate heat and their cost to build. On the first point, they have to be able to get rid of the heat faster, it's concentrated in a much smaller area. Compare the square area of a disc brake pad to the area of the 2 brake shoes. Scientifically speaking, brakes work by turning rolling energy into heat. Stopping 25,000 lbs from 60 mph in a given distance creates the same amount of heat regardless of what type of brakes you've got. All of the heat in those big brakes shoes is now in that small pad. You need to be able to get rid of it faster.
The real reason car manufactureers went to disc brakes up front was cost. I counted the number of pieces in my front drum brakes on my 67 442. Excluding shoes and drums there are 21 pieces of hardware on one front brake. Compare that to 4 for a single piston floating caliper on say a 70 442. Assembly time. If you've done brakes on both those systems you know what I'm talking about. Complexity of parts. Would it be easier to make 2 flat pads or 2 curved shoes with the linings precisely ground to match the arc of the drum? Savings were huge. The reason you didn't see them on the rears is that by the time they added in a parking brake system on a disc brake the savings were minimal. Stopping distances were no better. You can lock them up on a drum brake just as easily as a disc. For extreme heat applications (racing, etc) drum cars were fitted with vented backing plates and metalic shoes.
We often mistakenly assume because it's a newer technology it's better. I almost spit my beer out when a friend told me he was looking at a kit to convert his 68 mustang to newer style McPherson strut front suspension. Here is a prime example of cost cutting vs performance. Manufacturers adopted struts because it saved them 2 ball joints, 2 control arms, 4 bushings and a lot of time. The system does not keep the wheel perpendicular to the road as well as the older unequel length double control arm, but it does it adequately for a lot less money. You never see race cars (other than stock class) or high end high performance (Corvette, Viper)vehicles with them. Now there's an industry devoted to helping people replace their superior frt suspension with a cheaper poorly functioning system and relieving them of their hard earned $ in the process.

Having said all that, Yes I know it was a lot and I apologize,If you like the sound of an air brake and that big rig feel that comes with it, that's reason enough to put air brakes in your old truck.
Steve g.

kb3csw personally I hate automatic slack adjusters they give a guy a false sense of security. IMO a diver should be under the truck doing a full inspection at least once a month on a highway truck and twice for dump trucks or log trucks. Having to adjust brakes IMO maid this happen a lot more that drivers tend to do with automatics.

Let's get back to the first post, I am not concerned with the difference between disc or drums or the legal stuff to do with air brakes.

Any ideas or thoughts on the new style air disc brakes?

I already have 13" disc brakes on all 4 wheels of my truck right now, the idea I had was changing to air calipers.

Grigg

Steve, you appear to know what you're talking about, and you've obviously done your homework. However, I wonder if you could address some questions I have regarding performance of drum vs. disk brakes. I'm old enough to have driven new vehicles with both systems, and my experience tells me that disk brakes are superior to drum brakes.

Back in the old days, good drivers were very careful about applying the brakes too much because of brake fade. You knew that if you used the brakes too much, you'd lose them due to heat buildup. Also, the motion of the drum tends to push the shoes away from the braking surface, making it necessary to apply more force to get the same braking than is required with disks, which "drag" along the rotating surface.

Finally, racing enthusiasts (like myself) know that race cars adopted disk brakes long before personal vehicles did. I never thought of racing as a place where cutting costs was even a consideration. I think racing adopted disk brakes because they were superior to drum brakes.

Clearly, hydraulics allow you to apply a great deal more pressure than compressed air, but the amount of force applied is only part of the problem. You also have to be concerned about the braking surface area and the materials used in the friction material.

Disk brakes offer a great deal more surface area for braking than drum brakes do (10 times as much?). Furthermore, almost all of the drum brake surface is engaged in braking all the time, allowing very little surface area for heat dissipation. To make matters worse, the enclosed drum system does not allow the use of air flow to cool the brake system except on the outside surface of the drum.

That is why you had to worry about brake fade. Under extended use, such as going down a large grade, a perfectly good, well maintained set of drum brakes could fail completely due to heat failure. That's why so many highways in mountainous areas had big "sand traps" built to "catch" runaway trucks. We used to read about those runaway incidents regularly when I was a kid. I don't recall the last time I heard about a runaway vehicle.

Disks, OTOH, only engage a small percentage of the braking surface at any given time, allowing the rest of the braking surface an opportunity to cool. I'm not aware of any case, or any literature, that discusses brake fading with disk brakes. If you're a NASCAR fan like me, you know that they can run with disks glowing orange and still have full braking power. I doubt seriously you could do that with drum brakes.

So I'm having some difficulty accepting your position that drum brakes are superior to disk. (Or perhaps I misread what you are saying?)

In other areas, I agree with you. For example, I think the king pin setup on my '48 is as good, if not better, than the newer ball joint/control arm or Macpherson strut setup. That's why I haven't changed it. I'm also not convinced that rack and pinion steering is any better than the old drag link/pitman arm setup.

I look forward to your response.

We've hijacked his thread. I'll start a new post with my take on your questions.
Steve

One place air is superior to hydraulic is in withstanding heat like you could see on a long down grade. I have seen brake fluid boil in wheel cylinders and the pedal goes to the floor until it cools. I don't think you want double acting or spring brakes on a steer axle so the air discs should work there. We don't have air disc brakes on the drive axles on any of the trucks where I work so I don't know if they would be a good choice on the rear, but air dics on front an air drums on back should be workable. Looking at the Haldex brochure you linked, it looks like they use a standard air chamber to operate so you would think it would be a simple matter to swap it out for a piggyback chamber on the rear to have spring brakes. The brochure dosen't go into a lot of detail but it says they can can be used on every axle so I would expect they offer them with spring brakes where spring brakes are DOT required equipment. We may have them on some of the new trucks, but for the most part we aren't using discs yet where I work. It sounds like new stopping distance requirements will have them on new equipment in the very near future.

Let's revisit the air disc brake idea.

I last researched this about a year and a half ago, at that time I thought Haldex would offer the best air caliper. From a phone conversation with Dan Norman at Haldex in the US he said they had some in use in 22.5" wheels over here, but not a lot yet. And that he expected to see some retrofit kits available in 2009/2010 for semi trucks. He also said they had a 19.5" caliper but it had not made it's way across the pond from Sweden yet, and I should look for it about the same time.
That time is about now, so I've done some more looking.

Haldex model DB19:
http://www.haldex.com/en/North-Amer...ems/Product-Information/Air-Disc-Brake1/
and
http://www.haldex.com/Documents/hbsna/Disc_Brake/L20440_ModulX_Air_Disc_Brakes_Brochure_2-09.pdf

Wabco (and ArvinMeritor?) model PAN 19-1 plus (they even offer one for a 17.5" wheel package):
http://www.wabco-auto.com/products_and_systems/products-systems-air-disc-brake-pan-19-1-plus
and
http://www.wabco.info/intl/pdf/820/00/32/8200100323.pdf

Bendix-Dana-Spicer-Eaton-Roadranger (But only for 22.5" wheels):
http://www.roadranger.com/Roadranger/productssolutions/brakes/airdiscbrakes/index.htm

I think the Haldex DB19 will be the one to try first.
the idea is I can use my original rotors that just fit in the old 19.5" wheels, so the 19.5" caliper size should fit nicely over the rotor. I'll have to make my own caliper brackets.

We're headed to the Mid-America Trucking Show this weekend, so I'll learn what I can from the different manufacturers about these newly available air disc brake calipers to fit in 19.5" wheels. But I don't see Haldex among the thousand or so exhibitors listed, hope I'll find them there anyhow..

If it looks like this is a good idea the next step will be finding a set of calipers without loosing an arm and a leg.
Any ideas?

Grigg

We had a bus (Trailways style) stop in front of our store with a wheel locked up. It had disc brakes. I crawled under the bus with a hammer and tapped around on the caliper and the wheel freed up.

It had just snowed so I didn't spend a lot of time looking at the brakes, but they looked like the Haldex ones in the link(s) above. My first impression that these were just like the old wedge brakes, which were junk compared to the s-cam style.