New brake wear in period?

[Tony w]

Hello,
I was hoping I could get some advice for a frustrating problem with my a122S Lockwood a-frame camper. My brakes were not working right this spring and I had a hub that was heating up, so I took it into a reputable trailer repair shop here in bozeman. They discovered that my pads were totally worn down, which they said was causing the issues with heating and poor brake performance. The bearings and spindles were all fine. I believe the original axle is an Al Ko. They did not have Al Ko parts, so they replaced the drums and brake assembly and pads with Dexter parts. they said they would work fine on my camper. On their brake controller test unit, they were able to lock the brakes up no problem. I hooked my 2010 suburban up to the camper with the new brakes and found I only had 10% of the braking power I would expect. When I actuate the brake controller manually while rolling at 10-15 miles an hour, the camper would barely stop the vehicle. My old brakes would just about skid the trailer when tested like that. When I talked to the shop owner, he said it must be a bad controller. The one I had was 10 years old, so that made sense, especially with all the brakes on the camper being brand new.

When I got home I installed the new brake controller and I had the same result. It will eventually stop my suburban, but there is far less braking power than I have ever seen in any trailer I ever owned. This is with new drums, brake assemblies, pads and Tekonsha controller. By the way, the new controller was not showing and error codes.

I then had the neighbor, who tows a travel trailer, hook his vehicle up to my camper, and we got the same brake performance; maybe 10% of what you might expect. It seems I have isolated the problem to the camper and I can think of a few possibilities.
1. Maybe this camper requires al Ko brake parts. The repair shop said that was not the issue.
2. maybe the drums and pads need to wear in longer? The repair shop said I should drive it around for 50 miles and see if it starts to get batter.
3. Maybe my suburban is not putting out the voltage needed? Maybe a short? But....my neighbor got the same results with his vehicle, which we know works his camper brakes just fine.
4. Maybe they just need to be tightened up by the repair shop. They said they tightened them as far as they like until they are broken in. They also pointed out that they could lock the tires on their test machine, but locking up so you cant roll them by hand doesn't seem like it would take much testing power.
5. My brakes are haunted.

I would sure appreciate any input that anyone might have before I go to the trouble of taking it to another shop.
Thanks and have a great holiday, Tony

[MtBiker]

You need to find a nice empty road and do at least 10 stops from 35-40mph down to 15-20mph using the brake controller. This will help seat the brakes.
Go out and hit them hard so they don't Glaze over.
Search for burnish in brake pads for more info.
Read the controller manual carefully to be sure your settings are correct.

[Tony w]

Thanks for the reply. I know I have my controller cranked up all the way, so the brakes should be pretty strong. I will go a head and do what you suggested.

[TitanMike]

New drum brake linings need to be burnished before they achieve full braking power. It's a matter of making the radius of the shoes fit the radius of the drum better.

As stated go out and perform several heavy braking actions. I use the lever on the controller rather than stepping on the brake pedal. Avoid overheating the brakes while doing this by driving a mile or two at speed before repeating a series of heavy stops (4-5 at a time).

If you have trouble getting the manually applied brakes to stop, it may be that the power lead from battery to controller and from controller to rear connection on your tow vehicle isn't heavy enough to provide the up to 12+ amps needed for a full application.

Make sure the contacts on trailer connection cord and socket on truck are CLEAN! Any corrosion here will reduce electric power to brakes.

[D W]

I'm wondering if they just had their test unit cranked up all the way when they tested them? Nobody sets their controller to full power. My guess is that they didn't do a proper "initial adjustment" at time of install.

As TitanMike stated, new shoes will have to "burnished" for optimal braking efficiency.

[Tony w]

They said they had it set to around 50% of power, which has worked well for them in the past.

[kcmusa]

I’m guessing here, was brake magnetic changed with the other parts?
If you pull the pin from the brake away, can you move the trailer?
Do you have a meter to check the voltage, amps at the brakes.

[Larry-NC]

The pre-assembled brake/backing plate assemblies you got come as left-side and right-side assemblies. If they were inadvertently installed on the wrong sides you would have barely effective braking.

Find the instructions online and pull a wheel and brake drum and see whether yours were installed correctly.

[Tony w]

OK. I had a chance to do a little more testing and have some additional information below.
1. I went and burnished the brake pads as described in this thread, which slightly improved the braking ability. It is now around 20 % of what I would expect.
2. I pulled the breakaway pin and got around 20% of braking power. My batteries on the trailer are fully charged and in good shape.
3. The brake assemblies they installed included the pads and magnets. All new guts.
4. At the end of my burnishing trial, I could hear the brake pads kind of "slapping" into place as I pushed the thumb control in.
5. I do have a voltmeter but am not very good with it. I know how to measure voltage on it. I can probably figure out how to do amps as well.

6. Interesting comment about the right and left. The kid who installed these has been on the job around 5 months. When I asked the owner if there was an right and left, he hesitated for just a minute before saying they were installed correctly.

7. I have never worked on electric trailer brakes before. I am moderately mechanically inclined, but am no pro for sure. Is this something that is hard to do? On a scaled of 1-10, where would it fall?

Thanks to everyone trying to help.

[Larry-NC]

Originally Posted by Tony w

OK. I had a chance to do a little more testing and have some additional information below.
1. I went and burnished the brake pads as described in this thread, which slightly improved the braking ability. It is now around 20 % of what I would expect.
2. I pulled the breakaway pin and got around 20% of braking power. My batteries on the trailer are fully charged and in good shape.
3. The brake assemblies they installed included the pads and magnets. All new guts.
4. At the end of my burnishing trial, I could hear the brake pads kind of "slapping" into place as I pushed the thumb control in.
5. I do have a voltmeter but am not very good with it. I know how to measure voltage on it. I can probably figure out how to do amps as well.

6. Interesting comment about the right and left. The kid who installed these has been on the job around 5 months. When I asked the owner if there was an right and left, he hesitated for just a minute before saying they were installed correctly.

7. I have never worked on electric trailer brakes before. I am moderately mechanically inclined, but am no pro for sure. Is this something that is hard to do? On a scaled of 1-10, where would it fall?

Thanks to everyone trying to help.

If you've ever worked on drum brakes on a car, trailer brakes are very similar. They are the Bendix "servo" style brakes that were introduced around 1950. That is, the pair of shoes are anchored only at one point, the anchor pin at the top. When the brakes are applied, the rotation of the drum on the rear (trailing) shoe causes the assembly to force the front (leading) shoe to press on the drum. In automobiles, the shoes were even made of different materials. When you changed shoes, you had to make sure the shoe with "Primary" lining was in front and the one with "Secondary" lining was in back.

The major difference between car and trailer drum brakes is that in automotive brakes the shoe assembly was expanded by a hydraulic cylinder. In a trailer, there's a cam between the shoes. The cam is connected to an arm with an electromagnet on the end. When the brakes are applied, the magnet grabs the rotating drum, which moves the arm which rotates the cam which expands the shoe assembly.

If you've never done drum brakes, this explanation may not be very helpful.

--------------
Measuring amps vs volts.

With volts, you are measuring across a source which may have a load connected. Measuring across a battery, for example, or across a bulb which is connected to a battery. In these cases, it's a "parallel" connection which does not change the initial circuit. It's traditional to think of this as similar to water pressure.

With amps, you are measuring the current in a circuit. You have to break the circuit and insert the meter in the circuit so all the current through the circuit flows through the meter. It's a "series" circuit. It's traditional to think of this as water flow.

The common multimeter has several low-current (low amperage) scales, measuring in milliamperes (mA). The largest of these has a maximum of 2000 mA, or 2 Amps. This is too low for measuring brakes. There's a separate scale that can read up to 10 Amps DC that you must use. Black lead goes into COM. Red lead goes into DC 10A. Then find a connector in the circuit. Disconnect that connector: one lead goes into one side of the connector--the other lead goes into the other side, so that the meter is inserted into the circuit.

It doesn't matter which lead goes where. One way the reading will be prefixed by a "-" sign; the other way it won't. In the case of brakes, we don't need to care about the current direction, just the amount.

[TitanMike]

Originally Posted by Tony w

OK. I had a chance to do a little more testing and have some additional information below.


6. Interesting comment about the right and left. The kid who installed these has been on the job around 5 months. When I asked the owner if there was an right and left, he hesitated for just a minute before saying they were installed correctly.

7. I have never worked on electric trailer brakes before. I am moderately mechanically inclined, but am no pro for sure. Is this something that is hard to do? On a scaled of 1-10, where would it fall?

Thanks to everyone trying to help.

If you want to check to make sure the backing plates with shoes are installed correctly, remove the drums.

The brake shoes consist of a "Primary Shoe" and a "Secondary Shoe". The primary show should be installed to the front and secondary to the rear, using of course the direction of travel for the trailer as front/rear reference. NOT just "Right or Left".

When brakes are applied the primary shoe has a slightly higher coefficient of friction and grabs the drum surface, then pushing the secondary shoe into the drum surface. This is how a Single Servo brake system works. Even though electric, with no hydraulic cylinder like shown in most diagrams of the single/dual servo brake systems the principle is the same. The front shoe becomes the actuator, the rear shoe is the "Power" shoe.

Here's a pic of an electric brake loaded backing plate that should be similar to yours for a Right Side of the axle. Note the short lining on the RH side which should be facing forward when installed.


Since you have reduced braking I'd certainly eliminate this possibility.


If you hear the shoes "slapping" when you apply brakes, would also be a good idea to adjust them as even if they have auto adjust, they may have too much "slack". The electric actuator can only move the shoes so far unlike hydraulic brakes which can often be pumped up to make the piston move farther.

[Larry-NC]

Originally Posted by TitanMike

If you want to check to make sure the backing plates with shoes are installed correctly, remove the drums.

The brake shoes consist of a "Primary Shoe" and a "Secondary Shoe". The primary show should be installed to the front and secondary to the rear, using of course the direction of travel for the trailer as front/rear reference. NOT just "Right or Left".

When brakes are applied the primary shoe has a slightly higher coefficient of friction and grabs the drum surface, then pushing the secondary shoe into the drum surface. This is how a Dual Servo brake system works.

Here's a pic of an electric brake loaded backing plate that should be similar to yours for a Right Side of the axle. Note the short lining on the RH side which should be facing forward when installed.

Since you have reduced braking I'd certainly eliminate this possibility.


If you hear the shoes "slapping" when you apply brakes, would also be a good idea to adjust them as even if they have auto adjust, they may have too much "slack". The electric actuator can only move the shoes so far unlike hydraulic brakes which can often be pumped up to make the piston move farther.

The labels "Primary" and "Secondary" are printed in white pain on the EDGE of the shoes in tiny print. Look carefully and you should be able to see it.

[emm-dee]

Originally Posted by Tony w

OK. I had a chance to do a little more testing and have some additional information below.

..........

2. I pulled the breakaway pin and got around 20% of braking power. My batteries on the trailer are fully charged and in good shape.

........

Getting that result by activating the breakaway system is not good. The breakaway will send the full 12+ volts if pulled. It definitely should completely lock the tires.

Have you checked to ensure you have a good ground connection?

[TitanMike]

Originally Posted by Larry-NC

The labels "Primary" and "Secondary" are printed in white pain on the EDGE of the shoes in tiny print. Look carefully and you should be able to see it.

Some are, some aren't. Simpler to just put the shoe with the shorter lining at the front. That's universal and you can do that even with bad eyes.

[Tony w]

OK. It gets worse. I burnished the pads by slowing down from 45 to 25 mph with the thumb switch. Repeat 5 times, then drive a mile without braking, then do it again. I had a marginal improvement in the braking power. Went from 10-20 % of what I would expect.
I decided to pull a drum on one side to check that there had not been a right/left mistake when installing the brake assemblies. The drivers side is installed correctly, so the other side was probably also done correctly.

But- The entire larger back pad was almost totally gone! It was down to metal on metal. The smaller front pad was not very worn. The magnet looked like it melted and had metal dripping on the bottom. It got hot.

So now I am going to need new brake assemblies on both sides. These were installed just 20 miles ago. Any ideas about what might cause this would be helpful.

[TitanMike]

First guess would be improper adjustment and bra kg es were dragging seriously. After only 20 miles I'd be having a serious talk with the shop that installed them.

Hot brakes don't stop very well.

[Hclarkx]

I installed four new populated backing plates and drums from Dexter. I then had almost no brakes for 500 miles even with the controller on level 10. At 1000 miles I had a bit more braking but still woefully insufficient even with the controller on level 10. Better at 1500 but not great, controller still on 10. At 2000 miles things got better but not great. Controller still on level 10. At 2500 miles still weak and controller still on 10.

It then occurred to me that maybe the auto adjusters were not working, or I was not backing up often enough to take up the slack from shoe break-in. I backed up and hit the trailer brakes about 30 or 40 times and the brakes got much better; not what I'd like, but at least I can feel the trailer brake. Though the controller is still on level 8.

My best guess is that the brake shoes were not ground to mate well with the drums. We used to call this "arcing the shoes" IIRC. So there was very little shoe-drum contact at first and it took a whole lot of shoe wear to get full shoe-drum contact (I'm not sure I have full contact yet). And the adjusters were not able to keep up with that massive wear given my typical occasional backing thus compounding the problem.

Poor quality control. Somebody at Dexter must know that the shoes have to be ground to match the drums to work well out of the box.

Footnote .... the replacement backing plate and drum kits I got do not have star wheels so manual adjustment of the self-adjusting brakes was not possible. I had to back down a modest grade, hitting the trailer brakes again and again to take up the slack with the self adjusters.

[TitanMike]

Originally Posted by Hclarkx

It then occurred to me that maybe the auto adjusters were not working, or I was not backing up often enough to take up the slack from shoe break-in. I backed up and hit the trailer brakes about 30 or 40 times and the brakes got much better; not what I'd like, but at least I can feel the trailer brake. Though the controller is still on level 8.

My best guess is that the brake shoes were not ground to mate well with the drums. We used to call this "arcing the shoes" IIRC. So there was very little shoe-drum contact at first and it took a whole lot of shoe wear to get full shoe-drum contact (I'm not sure I have full contact yet). And the adjusters were not able to keep up with that massive wear given my typical occasional backing thus compounding the problem.

Poor quality control. Somebody at Dexter must know that the shoes have to be ground to match the drums to work well out of the box.

Footnote .... the replacement backing plate and drum kits I got do not have star wheels so manual adjustment of the self-adjusting brakes was not possible. I had to back down a modest grade, hitting the trailer brakes again and again to take up the slack with the self adjusters.

Shoe Arc Grinding was more a practice when brake shoes were re-lined in the shops using rivets. Also, bonded linings were sold as "Semi's" which had a thick lining that had to be ground to fit the drums. This was back in the days when drums were turned with pretty much no limit as to how much material was removed and the drum diameters could vary by as much as a half inch.

Today drums are far lighter and the amount of material that can be removed when turning is severely limited. Depending on the drum the max can vary from ~ .015" to as much as .125" or more. Shoe arc grinding is no longer done in shops due to the health hazard and combined with the limited amount of turning shoes really don't need to be ground.

In reality a properly fitted set of brake shoes do not fully contact the drum but have a certain amount of "heel and toe clearance". When applied the center of the shoes contact the drum and as more braking effort is applied the shoes flex and apply more braking force in a progressive manner. This is how the "Servo action" works in modern drum brakes.

Some old-timers (like me) used to "fit" shoes to the drum. Place the shoe in the drum, measure Heel-Toe clearance, then place the shoe in a vise and literally bend it until it's radius more closely matched the drum, with the proper heel/toe clearance. Works great on riveted linings. On bonded linings not so much.


The auto adjuster's on Dexter Nev R Adjust brakes use more of a ramp/notch style of wheel. Yes they aren't like the traditional star wheel but one can still adjust using a regular brake spoon. If too tight then a small pocket screwdriver needs to be inserted in the adjusting hole so the adjustment link can be disengaged from the wheel and using a second screwdriver, back the wheel off.

Also, Dexter brakes are supposed to adjust in either direction of travel/stopping. The amount of adjustment is very small with each stop so it may take a lot more than expected. This is a function of the number of "notches" on the adjustment wheel.

[Hclarkx]

Originally Posted by TitanMike

Shoe Arc Grinding was more a practice when brake shoes were re-lined in the shops using rivets. Also, bonded linings were sold as "Semi's" which had a thick lining that had to be ground to fit the drums. This was back in the days when drums were turned with pretty much no limit as to how much material was removed and the drum diameters could vary by as much as a half inch.

Today drums are far lighter and the amount of material that can be removed when turning is severely limited. Depending on the drum the max can vary from ~ .015" to as much as .125" or more. Shoe arc grinding is no longer done in shops due to the health hazard and combined with the limited amount of turning shoes really don't need to be ground.

In reality a properly fitted set of brake shoes do not fully contact the drum but have a certain amount of "heel and toe clearance". When applied the center of the shoes contact the drum and as more braking effort is applied the shoes flex and apply more braking force in a progressive manner. This is how the "Servo action" works in modern drum brakes.

Some old-timers (like me) used to "fit" shoes to the drum. Place the shoe in the drum, measure Heel-Toe clearance, then place the shoe in a vise and literally bend it until it's radius more closely matched the drum, with the proper heel/toe clearance. Works great on riveted linings. On bonded linings not so much.


The auto adjuster's on Dexter Nev R Adjust brakes use more of a ramp/notch style of wheel. Yes they aren't like the traditional star wheel but one can still adjust using a regular brake spoon. If too tight then a small pocket screwdriver needs to be inserted in the adjusting hole so the adjustment link can be disengaged from the wheel and using a second screwdriver, back the wheel off.

Also, Dexter brakes are supposed to adjust in either direction of travel/stopping. The amount of adjustment is very small with each stop so it may take a lot more than expected. This is a function of the number of "notches" on the adjustment wheel.

I've adjusted self-adjusting drum brakes with a screw driver lots of times ... not these. There was nothing visible through either access slot to get any kind of tool on. Pretty much just a smooth shaft.

Break-in was always an issue with drum brakes, but not 2500 miles. The leading shoe was not critical, but the trailing one that does the work was. I wish I'd looked closer when I put them on. And that I wasn't half way out a 2000 mile excursion when I realized that the shoes were not breaking in as they should.

The fact that it took 2500 miles (and lots of adjustment) to get helpful braking from the trailer tells me something was not right with the shoes from the factory. Maybe the OP has run into a similar problem.

[Zoinks]

Originally Posted by Tony w

OK. It gets worse. I burnished the pads by slowing down from 45 to 25 mph with the thumb switch. Repeat 5 times, then drive a mile without braking, then do it again. I had a marginal improvement in the braking power. Went from 10-20 % of what I would expect.
I decided to pull a drum on one side to check that there had not been a right/left mistake when installing the brake assemblies. The drivers side is installed correctly, so the other side was probably also done correctly.

But- The entire larger back pad was almost totally gone! It was down to metal on metal. The smaller front pad was not very worn. The magnet looked like it melted and had metal dripping on the bottom. It got hot.

So now I am going to need new brake assemblies on both sides. These were installed just 20 miles ago. Any ideas about what might cause this would be helpful.

Here's a really odd thing to check. On my A213HW, I had brake issues when our trailer was brand new off the dealers lot. I had an infrared temp gun and could see the left and right brakes had significantly different temperatures. The dealer troubleshooted this issue 5 or so times before finally tripping on the cause. The factory installed the wrong brakes on one side. I don't recall all of the details but one side had 4 ohm magnets and the other side had 8 ohm magnets, or something like that. So, one side was essentially doing all of the braking and over heating. Might be worth a check. After they put matching systems on both sides everything worked fine.