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Old 07-26-2010, 10:29 PM   #15
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I had the old Hydraulic disc brakes on my 77. Nothing but problems on the road. No one has parts or can service them. There is also a fatigue crack flaw that develops in the welding of the caliper holders. I dumped them and went electric. Good enough for 30,000 miles behind a 3/4 ton van. Maybe the new disk brake systems are better now but I would not fool around trying to get the old ones to stay working.
Some repair parts are still available for the Airstream original disc brakes, such as the bushings, clevis pins, boots, O rings, pads, and the sync valve is easily overhauled.

The flaw you mentioned, is related to lack of proper running gear balance.

The original disc brakes, work great with the Carlisle actuator, eliminating the need for vacuum supply from the tow vehicle.

Andy
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Old 07-27-2010, 12:02 AM   #16
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When we replaced the axles on our '71 Tradewind this spring, I sprung for the disc brake setup - and they really work. The brakes can be adjusted so one doesn't feel the weight of the trailer at all, other than the first second or so as the trailer brakes come on. I've not yet aggressively tested stopping distances, but I'd not be surprised to find them the same as the truck unloaded.

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Old 07-27-2010, 12:06 AM   #17
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...I've not yet aggressively tested stopping distances, but I'd not be surprised to find them the same as the truck unloaded...
depending of TRUCK/trailer combo this has been tried/measured ...

an f-250 plus stream stop in shorter distances that the f-250 solo.

there was an article in trailer life? 5-6 years ago that looked at this issue

cheers
2air'
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Old 07-28-2010, 09:43 PM   #18
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depending of TRUCK/trailer combo this has been tried/measured ...

an f-250 plus stream stop in shorter distances that the f-250 solo.

there was an article in trailer life? 5-6 years ago that looked at this issue

cheers
2air'
We knew this to be so in the 1960's. A common goal or reference then. It's always worth going through every detail in re brakes. Drum brakes on car and drums on trailer, or all disc, it is the standard to meet.
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Old 08-02-2010, 05:05 AM   #19
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I wish to correct an incorrect statement made by Andy. The early design disc brake caliper holder design was made from flat steel stock with slider pins welded to it. This part has a design flaw in that the loads that are generated by the pins must be transmitted through a very narrow weld where in transitions to the flat plate. This causes excessive bending moments and high stress in the weld whenever the brakes are applied. As you can plainly see it has nothing to do with the imbalance of the wheels or rotating elements. Andy is simply wrong. Andy is the person who has the most parts available to service these old brake systems. If you want parts for them see Andy. As a mechanical engineer with a background in failure analysis at a major manufacturer of trailers, I can not recommend anyone continue to use this design when I know it is likely to fail as the most inopportune time and potentially cause a bad accident.

I personally had one of them fail scattering parts and hydraulic fluid all over the road resulting in complete brake failure. Fortunately, I was able to steer off the road and avoid the collision with the truck which had applied his brake in front of me. The stress from the aggressive braking I was doing at that time was the last straw that caused the already compromised caliper holders to fail. Microscopic analysis of the failed parts revealed fatigue cracks weakened the assemble and these same cracks were found in two of the three remaining assemblies which lead to my conclusion to completely scrap the system and go to electrics.

This is a warning to all people with high mileage trailers with the old disc brake systems: Scrap the system before you have a serious accident.
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Old 08-02-2010, 09:16 AM   #20
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I wish to correct an incorrect statement made by Andy. The early design disc brake caliper holder design was made from flat steel stock with slider pins welded to it. This part has a design flaw in that the loads that are generated by the pins must be transmitted through a very narrow weld where in transitions to the flat plate. This causes excessive bending moments and high stress in the weld whenever the brakes are applied. As you can plainly see it has nothing to do with the imbalance of the wheels or rotating elements. Andy is simply wrong. Andy is the person who has the most parts available to service these old brake systems. If you want parts for them see Andy. As a mechanical engineer with a background in failure analysis at a major manufacturer of trailers, I can not recommend anyone continue to use this design when I know it is likely to fail as the most inopportune time and potentially cause a bad accident.

I personally had one of them fail scattering parts and hydraulic fluid all over the road resulting in complete brake failure. Fortunately, I was able to steer off the road and avoid the collision with the truck which had applied his brake in front of me. The stress from the aggressive braking I was doing at that time was the last straw that caused the already compromised caliper holders to fail. Microscopic analysis of the failed parts revealed fatigue cracks weakened the assemble and these same cracks were found in two of the three remaining assemblies which lead to my conclusion to completely scrap the system and go to electrics.

This is a warning to all people with high mileage trailers with the old disc brake systems: Scrap the system before you have a serious accident.
The disc brake pad "slider pins" are threaded into the plate, and then welded.

Granted, it is a weak spot, but only because the welded area is smaller than it should be.

However, the failure rated has been extrememly small. On the other hand, the design of the entire system, is way over 30 years old, and a replacement, as you stated, should be considered, to maximize safety.

Andy
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Old 08-02-2010, 09:30 AM   #21
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Andy, Thanks for agreeing with me. Any trailer that is still out there with 30 years of abuse on these brake parts should have this system removed. You can either replace it with an electric brake system for about $400 or go to one of the new design disc brake systems for considerably more. Brakes are a very important part of the overall safety system and you should make sure they will work when you need them or you could be risking your rig and your life.
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Old 08-02-2010, 10:16 AM   #22
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Quote:
Originally Posted by 2airishuman View Post
depending of TRUCK/trailer combo this has been tried/measured ...

an f-250 plus stream stop in shorter distances that the f-250 solo.

there was an article in trailer life? 5-6 years ago that looked at this issue

cheers
2air'
I'd like to find that article. Having a F250 and a 28 footer my experience has been positive.
My trailer has the old style disc brakes. Proper inspection, maintenance and use not abuse is key. I wouldn't have electric brakes on anything. Drum brakes are old technology too. When my factory brakes are no longer serviceable, discs will be the replacement. Sure these early style discs have inherit design flaws and so does my Prius.
Something about a wire and a magnet to control friction in a rotating device makes me nervous. If it's so great,why hasn't the automotive industry adopted it yet? (I'm not talking regenerative braking like the little import above ether)
Hydraulicdiscs are here to stay, Airstream got an early start with this idea.
Many years over the road as a commercial heavy equipment transport driver puts this in perspective for me. 7 to 9 axles worth of drum type brakes.
I've seen enough of what they do and don't perform!
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Old 08-02-2010, 01:37 PM   #23
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...............................................

Hydraulicdiscs are here to stay, ................................................
I don't think so.

I'm sure eventually they will be replaced by Hyperbolic Magnetic Depermeators with beam deflection actuators.

Mark my words.

Regards,

Ken
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Old 08-02-2010, 01:40 PM   #24
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I don't think so.

I'm sure eventually they will be replaced by Hyperbolic Magnetic Depermeators with beam deflection actuators.

Mark my words.

Regards,

Ken
Could be, but they will probably be made in China.

Andy
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Old 08-02-2010, 02:01 PM   #25
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Could be, but they will probably be made in China.

Andy
Well, the way the economy has been going, the cheap labor pool may be in the US by that time.

Ken
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Old 08-02-2010, 08:46 PM   #26
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Could be, but they will probably be made in China.

Andy
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Old 09-05-2015, 03:59 PM   #27
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I had the old Hydraulic disc brakes on my 77. Nothing but problems on the road. No one has parts or can service them. There is also a fatigue crack flaw that develops in the welding of the caliper holders. I dumped them and went electric. Good enough for 30,000 miles behind a 3/4 ton van. Maybe the new disk brake systems are better now but I would not fool around trying to get the old ones to stay working.
Can you explain how you went about changing it all out and where you got the parts? Thanks.
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Old 09-07-2015, 04:48 AM   #28
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It is very simple and can be done in an afternoon. I bought my first conversion parts from Kelsy Hayes. I think Dexter is a better choice now. My latest parts were bought from them. You have to buy new drums and backing plates. ($400 for tandem trailer) Quite heavy to ship and therefore more expense. The backing plates bolt to the axles without modification. The drums fit the axles and have new bearings provided. You just have to make up wiring to get from the umbilical to the brakes. I used 10 gauge wire. Remove the hydraulic lines and actuator. If you want to maintain discs, Dexter sells complete system.
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