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Old 07-24-2015, 07:21 AM   #29
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Originally Posted by nothermark View Post
Read your own article:
"This basic design proved capable under most circumstances, but it had one major flaw. Under high braking conditions, like descending a steep hill with a heavy load or repeated high-speed slow downs, drum brakes would often fade and lose effectiveness. "

I think that was what I said. The problem with disc brakes is that they need much higher pedal pressure without a booster. They are a large part of why power brakes became standard.
It is true that disc brakes need more pressure to work, but the pressure is increased, by the larger bore of the caliper piston.

Drum brakes, us a 1 inch or less diameter, piston, where a caliper piston is around 3 inches, or more. The hydraulic advantage helps with the pedal pressure issue.
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Old 07-24-2015, 12:02 PM   #30
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Quote:
Originally Posted by nothermark View Post
Read your own article:
"This basic design proved capable under most circumstances, but it had one major flaw. Under high braking conditions, like descending a steep hill with a heavy load or repeated high-speed slow downs, drum brakes would often fade and lose effectiveness. "

I think that was what I said. The problem with disc brakes is that they need much higher pedal pressure without a booster. They are a large part of why power brakes became standard.
Thank you...I read it and it clearly states the disc brakes are an evolution to the basic friction (drum) brake for many reasons.

The larger bore and/or 2-3 cylinders per caliper on each brake create the increased pressure needed without higher pedal pressures.

But, if a person wants drum brakes on a trailer, they are in luck. Drum brakes are available and less expensive to purchase than discs. But, maint of drum brakes will be a more complex task and could require more parts than just new brake shoes...another advantage of discs.

Safe travels
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Old 07-25-2015, 05:56 AM   #31
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Originally Posted by Scarab0088 View Post
Thank you...I read it and it clearly states the disc brakes are an evolution to the basic friction (drum) brake for many reasons.

The larger bore and/or 2-3 cylinders per caliper on each brake create the increased pressure needed without higher pedal pressures.

But, if a person wants drum brakes on a trailer, they are in luck. Drum brakes are available and less expensive to purchase than discs. But, maint of drum brakes will be a more complex task and could require more parts than just new brake shoes...another advantage of discs.

Safe travels
You still do not get it. There is no free lunch. Drums can be designed to use the force of the rotating drum to help increase the pressure. Discs cannot. More cylinders means more hydraulic displacement. More displacement means longer pedal travel or a bigger master cylinder thus higher pedal pressures yet. Power booster technology is the anwer.

All this is somewhat off the topic of tow dollies. There electric brakes give on the advantage of manually applying the brakes from the controller but one is dealing with drums and their problems. With Surge brakes one has to maintain the fluid level which seems to be significantly less than normal wear can use. At least I keep seeing mention that the reservoir was empty so there was no braking action. They also have their maintenance on the sliding tongue and whatever push they exert on the towing vehicle in the process of developing braking pressure. The real issue is knowing what they problems are with each system so one can pick their own problems.
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Old 07-25-2015, 01:16 PM   #32
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You still do not get it. There is no free lunch. Drums can be designed to use the force of the rotating drum to help increase the pressure. Discs cannot....

... With Surge brakes one has to maintain the fluid level which seems to be significantly less than normal wear can use. At least I keep seeing mention that the reservoir was empty so there was no braking action. They also have their maintenance on the sliding tongue and whatever push they exert on the towing vehicle in the process of developing braking pressure...
I will agree that I cannot see how stationary shoes (drum brakes) gain any braking force over stationary pads (disc brakes). Both apply friction to the spinning metal surface.

I submit that the slight angle engineered into brake shoes does not improve braking...only allows a smoother application...that is different. I have never seen comment about this before. Any additional reference would be welcome.

The comment about fluid replacement in surge brakes is very worrisome. If refilling the master on disc brakes was ever a routine thing...there was a leak

For our surge/disc brake trailer and dolly, the fluid is a good indicator that pad replacement is due...overfilling the fluid just makes a mess when changing the pads.
And, the tongue/master cylinder on a surge brake system only requires that it is clean and free to operate...really no maint at all.

Finally, if an owner prefers electric (drum) brakes...great. Many talk about manually engaging the trailer brakes to "keep the trailer in-line". I never did this with our previous TT's because using the trailer brakes without the tow vehicle brakes will only serve to wear the trailer brakes prematurely. If the trailer is pushing the tow vehicle around, that is a whole different discussion.

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Old 07-25-2015, 01:56 PM   #33
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I will agree that I cannot see how stationary shoes (drum brakes) gain any braking force over stationary pads (disc brakes). Both apply friction to the spinning metal surface.

I submit that the slight angle engineered into brake shoes does not improve braking...only allows a smoother application...that is different. I have never seen comment about this before. Any additional reference would be welcome.

The comment about fluid replacement in surge brakes is very worrisome. If refilling the master on disc brakes was ever a routine thing...there was a leak

For our surge/disc brake trailer and dolly, the fluid is a good indicator that pad replacement is due...overfilling the fluid just makes a mess when changing the pads.
And, the tongue/master cylinder on a surge brake system only requires that it is clean and free to operate...really no maint at all.

Finally, if an owner prefers electric (drum) brakes...great. Many talk about manually engaging the trailer brakes to "keep the trailer in-line". I never did this with our previous TT's because using the trailer brakes without the tow vehicle brakes will only serve to wear the trailer brakes prematurely. If the trailer is pushing the tow vehicle around, that is a whole different discussion.

Safe travels
On a disk brake system the pads are rigidly mounted to the caliper. In turn the caliper is rigidly mounted to the spindle or axle. All the pressure needed to activate the brakes originates from the amount of pressure applied by the hydraulic (or electric) system. There is no "self energizing feature with disk brakes.

On a drum brake system the shoes are not rigidly mounted to the backing plate. They are located with spring mounts and anchors in such a manner as to be able to slightly rotate (wrap) against the drum as pressure is applied. The wrapping or "self energizing" action pulls the shoes against the drum and reduces the amount of pressure that needs to be applied by the operator through the hydraulic (or electric) actuator.

Here's a partial quote from a manufacturers service manual:

DRUM BRAKES
This drum brake assembly is a leading/trailing shoe design.
Both brake shoes are held against the wheel cylinder
pistons by the lower return spring and the fixed
anchor plate near the lower return spring. When the
brakes are applied, the wheel cylinder pistons move
both shoes out to contact the drum. With forward wheel
rotation, the forward brake shoe will wrap into the drum
and become self-energized. With reverse wheel rotation,
the rear brake shoe is self-energized.

Here's a link to the section of the manual:

http://www.adriatic-company.it/matiz...m%20brakes.pdf


This system was invented long before any power assists systems were available. It was a necessary feature to give the brake shoes sufficient power to stop the vehicle without fatiguing the driver. Since the advent of disk brakes power assist has become a necessity.







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Old 07-25-2015, 02:18 PM   #34
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Self-energized I never gave it a name before
I am well aware of this action. It was used to operate the first auto-adjusters in early Ford's when backing. In practice it does little to increase force, but does much to smooth operation.

So... excluding my opinion...if (as some are saying) drum brakes are just as good as discs (and seem to have force multiplication properties), WHY would the world's vehicle makers move to a system that by all reports cost more?

Safe travels
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Old 07-25-2015, 03:28 PM   #35
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Self-energized I never gave it a name before
I am well aware of this action. It was used to operate the first auto-adjusters in early Ford's when backing. In practice it does little to increase force, but does much to smooth operation.

So... excluding my opinion...if (as some are saying) drum brakes are just as good as discs (and seem to have force multiplication properties), WHY would the world's vehicle makers move to a system that by all reports cost more?

Safe travels
I wouldn't say drums are as good as disks in all situations. They are certainly adequate for many applications. Disk brakes are superior when it comes to stopping or slowing heavy loads repeatedly in short periods of time. They have less propensity to fade because they cool far more rapidly.

Disk brakes were introduced as an option on performance vehicles and trucks that carried loads in excess of what a normal passenger car would carry. Today they are almost mandatory on front wheel drive cars since the front axle carries over 50% of the cars weight. In most applications the disks have more swept area than could be accomplished by a size drum system able to fit in the same space. They are also much lighter than a drum system designed to stop the same size load.

The disk brake systems today have far fewer parts than a drum system. This certainly makes production and assembly less costly. The smaller footprint, lighter weight, and the cost certainly play into the equation as far as the manufacturers are concerned.
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Old 07-25-2015, 05:52 PM   #36
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Has everybody forgot about wet brake shoes, compared to disc pads.

Don't remember riding the brakes. to dry the shoes?

Am I that old?
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Old 07-25-2015, 06:03 PM   #37
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Oh Yes!
Wet brake shoes, especially on a 4x4 when crossing water

The WORST was brake shoes wet from gear oil or hub grease on a trailer if/when the axle seal leaked. There was no drying those out

Drum brakes on all 4 corners was not that long ago...was it?

Safe travels
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Old 07-26-2015, 06:18 AM   #38
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Has everybody forgot about wet brake shoes, compared to disc pads.

Don't remember riding the brakes. to dry the shoes?

Am I that old?
I think most of us are close if not that old. Part of it probably depends on how well we were trained back then.

I think it might be a bit of chicken and egg argument but better machining processes and seal materials have made it cheaper to do the hydraulic bits in a disc brake system including the boosters. Discs were hot items on race cars and some sporty stuff in the 60's. Maybe 50's on some specialty cars. For all I know earlier but not common. I recall reading a lot about them then. I think somebody hit it with front drive cars needing them probably for fade more than anything else with all the braking load on the front.
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Old 07-26-2015, 08:27 AM   #39
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I cannot believe there is this much debate about brake technology on trailers.
Just to clear a few things up. Electric trailer brakes do not use brake fluid. They use a magnet that it is attached to the face of drum which in turn creates a drag that moves the brake pads to contact the drum surface. A lot of moving parts. They must also be adjusted an average of every 5,000 miles. 90% of people with electric brakes do not have brakes at all because the shoes are out of adjustment and they are not contacting the drum. The madness frequently fail and have to be replaced. Any trouble shooting starts with the controller, the entire length of the wiring and then the trailer wiring and then the brakes themselves.

The disc brakes system is 4 times more powerful then a drum system, never need adjusting and have very few moving parts. They cool off in seconds. The actuator requires zero attention except for occasionally topping up the brake fluid as the pads wear down.

Big trucks use drum brakes because they have to disconnect from the trailer. They are air activated, disc brakes cannot be air activated.

Having repaired trailers for nearly 20 years now I can tell you that ANY kind of drum brake system is inferior to disc brake systems for many reasons.
We offer Idler , Electric and Disc brake dollies because we are all different and we have our own preferences. We might sell 2 electric brake units a month out of hundreds.
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Old 07-26-2015, 12:46 PM   #40
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I cannot believe there is this much debate about brake technology on trailers.
Just to clear a few things up. Electric trailer brakes do not use brake fluid. They use a magnet that it is attached to the face of drum which in turn creates a drag that moves the brake pads to contact the drum surface. A lot of moving parts. They must also be adjusted an average of every 5,000 miles. 90% of people with electric brakes do not have brakes at all because the shoes are out of adjustment and they are not contacting the drum. The madness frequently fail and have to be replaced. Any trouble shooting starts with the controller, the entire length of the wiring and then the trailer wiring and then the brakes themselves.

The disc brakes system is 4 times more powerful then a drum system, never need adjusting and have very few moving parts. They cool off in seconds. The actuator requires zero attention except for occasionally topping up the brake fluid as the pads wear down.

Big trucks use drum brakes because they have to disconnect from the trailer. They are air activated, disc brakes cannot be air activated.

Having repaired trailers for nearly 20 years now I can tell you that ANY kind of drum brake system is inferior to disc brake systems for many reasons.
We offer Idler , Electric and Disc brake dollies because we are all different and we have our own preferences. We might sell 2 electric brake units a month out of hundreds.
Once again I think you are offering more opinion than fact. No one has said that electric brakes use any kind of hydraulics. The excerpt from a manufacturers service manual was intended to highlight the fact that drum brakes do require less mechanical force for application because of the mounting system and it's inherent ability to allow the shoes to assist the process by wrapping on the drums.

Drum brakes on trailers and dollies utilize the same mounting systems as those used on most automobiles. As such regardless of the power source (electric, hydraulic, or mechanical) the shoes once activated will wrap on the drums. The newer systems also incorporate self adjusting mechanisms which eliminates the need for any manual adjustment past the initial installation.

Air activated disk brakes do exist in the commercial trucking industry. They were first introduced on straight trucks and busses in the 1970's. They have been actively used on these applications since 1981. They are currently available as an option on over the road tractors and trailers. Bendix, Meritor, and Wabco are among the companies that offer air operated disk brakes for both tractors and trailers.

When comparing these systems it should be done using current examples of both types of technology. Not using the state of the art technology for one system and 40 year old technology for the other.
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Old 07-27-2015, 05:10 AM   #41
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I am not aware of any trailer manufacturer that has self adjusting brakes. I know that no dolly manufacturer does.
This is really a pointless debate. I really don't think anyone believes that drum brakes are superior to disc brakes.
My last comment. Im dropping this thread.
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Old 07-27-2015, 05:53 AM   #42
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Big trucks use drum brakes because they have to disconnect from the trailer. They are air activated, disc brakes cannot be air activated.
You were doing good, until this. Discs have been around in HD trucks since the 80s.

Almost all semis tractors now are coming out standard with disc brakes, because the Feds have mandated shorter stopping distances. These are ALL air activated!
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