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Last Post 16 Sep 2008 12:39 AM by  TeamRX8
Trailer brake problems
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Jim G
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08 Sep 2008 10:01 PM

    I've got trailer brake issues. I can hear and feel the brakes come on but they are ineffectual. If I get the rig going at about 20 mph and slide the manual control to full (with gain at full), the rig will slow but it'll take about 300' to stop (not using van brakes).

    My van has a new Prodigy in it. I checked the voltage coming into the brake controller and it was over 12 v. Checked the voltage at the rear of the tow vehicle: 12 v. Checked the voltage at the magnets: 11.5v.

    Adjusted the trailer brakes. Still poor braking. Braking does slow down the rig but not nearly enough. Just how tight must the brake shoes be adjusted? The other day I set them so that there was definitely a good bit of drag. Is there something else that could be wrong inside the hub?

    Oh. The shoes and magnets are brand new.

    Any ideas would be greatly appreciated.

    Thanks,
    Jim

    solonut52
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    09 Sep 2008 01:54 PM
    Check the ground connection for the magnet and also the ground between the trailer and the tow rig
    snaponbob
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    09 Sep 2008 02:41 PM

    Jim, solonut is right. But, having had similar issues with my trailer, I went back to basics. I jacked up the trailer and yanked the drums for a complete inspection. Two magnets, two sets of shoes, two drums, and freshening up all of the ground connections resulted in much better braking. Why? Well, the magnets were physically worn out which scored the drum faces, corrosion had compromised the grounds, and shoes were cooked which hot spotted the drums. I found a trailer place on line in Texas that had very good pricing and can find that link if you want it. One other thought. Do NOT assume that the 12 volt supply is good unless you checked it with a load. Good luck.

    Jim G
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    09 Sep 2008 03:01 PM

    To measure voltage at the wheel, I needed to use the trailer ground. Getting 12v means trailer ground is OK. And this was with the brake controller at full gain and with the manual slid all the way over to full. So I think my wiring is OK. If you think this method might still be problematic, please let me know. Electrical stuff is not my forte. But I thought i did it right this time.

    Forgot to mention that my magnets and shoes are brand new (about 3 weeks old). It could be the surface of the drum that the magnets face is not good so I'll check again tonight.

    Thanks,

    Jim

    snaponbob
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    09 Sep 2008 06:43 PM
    Jim G wrote:

    To measure voltage at the wheel, I needed to use the trailer ground. Getting 12v means trailer ground is OK. And this was with the brake controller at full gain and with the manual slid all the way over to full. So I think my wiring is OK. If you think this method might still be problematic, please let me know. Electrical stuff is not my forte. But I thought i did it right this time.

    Forgot to mention that my magnets and shoes are brand new (about 3 weeks old). It could be the surface of the drum that the magnets face is not good so I'll check again tonight.

    Thanks,

    Jim

    By referring to "with a load" I am suggesting that you check the output to the trailer brakes WHILE the trailer is hooked up to the tow vehicle. If you can't access a terminal at the connector you may be able to pierce thw power lead to the brakes. If, and that is a BIG if, there is a problem with the supply of 12 volts (bad, loose, or corroded connection to power) you would see something less than 12 volts. But pulling the drums is the right thing to do. If the surface that the magnet rubs on is all scarred up it is time for new drums. If the brake surface is glazed, blued from heat, or groozed from the old shoes, them ditto on new drums. And at the risk of hurting your feels, are the shoes on correctly? (Sorry about asking that one, but it can matter.) All of the this and the previoos post falls into the category of 'QUESTIONS FROM MY NOTEBOOK FROM THE SCHOOL OF HARD KNOCKS'.

    solonut52
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    09 Sep 2008 06:54 PM
    Jim G wrote:

    To measure voltage at the wheel, I needed to use the trailer ground. Getting 12v means trailer ground is OK. And this was with the brake controller at full gain and with the manual slid all the way over to full. So I think my wiring is OK. If you think this method might still be problematic, please let me know. Electrical stuff is not my forte. But I thought i did it right this time.

    Forgot to mention that my magnets and shoes are brand new (about 3 weeks old). It could be the surface of the drum that the magnets face is not good so I'll check again tonight.

    Thanks,

    Jim

    you may have 12v and still have a bad ground.....the load on the magnet will amlify that......My Dad tought me that 40 years ago when the elec brakes werent working right

    he cleaned the connections and we had brakes......and we needed good brakes where we went.......7-8% grades and switch back corners(great miata roads[:D])

    snaponbob
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    09 Sep 2008 07:13 PM
    I almost hate electric trailer brakes. (And having used surge brake trailers as well and they have their own issues.) When they aren't working right I hate them even more!!!! I had a 1976 Dodge D100 van (just a LOVELY machine!!) onto which I had an electric trailer brake actuator system that operated the actuator off of brake pressure from the front brake line pressure. More pressure = more voltage to the trailer brakes. Utterly predictable and completely linear. When I could keep the brakes on the trailer working properly it was great. That was many years ago. But hooking into a modern ABS system to run that type of system is "iffy" at best. The systems I have on my 97 Chevy Express Van is triggered by the brake light circuit, and my wife's Saturn Outlook (GMC Acadia clone) is essentially the same. I may have to re-investigate to see if there is a pressure sensitive system available for ABS system vehicles.
    Jim G
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    09 Sep 2008 07:21 PM

    OK, to clarify what I did yesterday ... trailer was plugged into tow vehicle. Slid the manual bar over and taped it into place full on. Ran one end of voltmeter from ground and the other end was pierced into the wire near one of the magnets. Got 12 v.

    An hour ago I pulled both drums. Checked shoes to make sure they could move, etc. Looked OK to me. Magnets OK. Drums where magnets ride were slightly scored but not bad. But that slightly scored face was not shiny in some concentric areas. That indicates some problem? I cleaned it all up and put it back together. Tightened shoes. Tested. No better.

    Solonut52 wrote:

    you may have 12v and still have a bad ground.....the load on the magnet will amlify that......My Dad tought me that 40 years ago when the elec brakes werent working right. he cleaned the connections and we had brakes

    -------------------

    OK, so cleaned the plug connections. And last Sunday I went to town re-working the main ground on the trailer. It's nice and clean.

    What now?



    snaponbob
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    09 Sep 2008 07:32 PM
    Run a new ground wire from the trailer ground to the chassis ground on the tow vehicle. I did this test on my current rig and discovered a ground issue both at the connector (can't remember which side) AND at the ground on the chassis. The corrections were to correct the ground at the connector and ran a new ground wire from the vehicel side of the connector to battery ground in the engine compartment. Solved.
    Jim G
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    09 Sep 2008 09:43 PM

    Just did some more stuff. First I did pin probes directly on the two magnet wires. Got only 9.8v. Manufacturer says it has to be between 11 and 12. So OK there's a ground problem that has to be attended to. But .... tell me if I'm wrong here, but that indicates I'm only losing 10% voltage and if that was the entire problem then the brakes (altho not as strong as they could be) should be working better than they are.

    So ... there must be another problem, would you guys agree?

    One thing I noticed when I installed the new shoes last month was that the brake shoe retaining spring and pins were very difficult to install. The coils on the little springs are bound up. Is it supposed to be like that? The reason I ask is because just now I tried to pry the brake shoes apart using my hands on one shoe and my foot on the other. I'd say it took about 40 to 50 lbs of force to accomplish this. Isn't that a bit much? Should the shoes be looser on the backing plate?

    Thanks for all the help. I really appreciate it.

    Jim


    snaponbob
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    10 Sep 2008 12:03 AM
    First, 12 volt systems really run at about 13 volts. You are down about 20% of the required voltage to properly activate the magnets. Try a new ground wire to a known good ground (the battery terminal). Next, if you still have all the old parts give everything a good inspection to see if everything is right. For starters, it sounds like the pins are too short or the springs were too long. Not knowing if the shoes are symetrical, they may be mixed up on the axles. Sounds like you need to open up a can of Cambell's "Start Over".
    Jim G
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    10 Sep 2008 09:43 PM

    OK, this is weird. A friend sent me to a guy who has a good and fairly large business with RVs and trailers. He said the guy would look at my trailer for free and only charge if he had to do work on it. So I drove the 30 minutes there and left it for him. He called me back later in the day and said he pulled the wheels and looked at the mechanicals. "All fine", he said. Then he measured amps at the magnets. "Very good", he said. "Up to spec".

    I asked if he had driven it. He claims he did. I asked if the stopping power of the brakes on the trailer felt OK to him. He said it felt about 80% and will get up to 100% as soon as the shoes break in. I told him I had driven with these shoes for close to 1000 miles, admittedly most were highway miles but some local roads too. I have probably used the brakes 100 times at least. He said from the looks of the shoes, they aren't broken in yet. And the lack of stopping power I feel is because my tow vehicle is 1400 pounds heavier than my last tow vehicle and so my 4000 pound (loaded) trailer just doesn't make much of an impact on my big van.

    How does that sound to you guys?

    It's hard to fathom for me because when I move along at 20 mph, lift off the throttle, and go full brake on the manual lever, the trailer just barely sheds some speed. The Prodigy literature says that it ought to lock up the brakes when I do that with full gain.

    I'm confused. As usual.

    Thoughts?

    Thanks,

    Jim

    snaponbob
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    10 Sep 2008 10:20 PM

    Jim, have you tried that same brake test with nothing on the trailer? If the brakes will not lock with nothing on it, the mechanic was full of crap. Notice my screen name. I have dealt with a few mechanics. Just like solo drivers, they are not all equal.

    Do you still have the old brake parts?

    Jim G
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    11 Sep 2008 08:51 AM

    All of my tests this week have been done with no car in the trailer, but my spares and spare tires were in the trailer. Still, it's pretty light right now. So your sentiments echo what I'm thinking.

    I have the old shoes and compared them with the new ones before installation. The old magnets were scored terribly and they were trashed.

    I've pretty much run out of time. I'm just going to load up the trailer and hit the road and make sure there's room between me and the cars in front of me. Thanks for the help, it was most appreciated.

    snaponbob
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    11 Sep 2008 09:39 AM
    When you get back check the old and new mabnets for resistance with an ohm meter. Also, replace the hold down springs and pins, and all of the brake springs with the old ones to see if it improves. Hopefully you have the front and back shoes properly placed. Good luck.
    Jim G
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    11 Sep 2008 09:59 AM

    Bob,

    In what way does the difference between the front and back shoes show up? I vaguely recall trying it both ways and one way just wasn't going to be able to be installed, even if I was to force it. But maybe I'm wrong.

    Jim

    marka
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    11 Sep 2008 10:22 AM

    Howdy,

    Enclosed trailer or open trailer?

    An open trailer that won't lock up the brakes with the trailer unloaded and full manual power has a problem, no question.

    An enclosed (or otherwise heavy) trailer that won't lock up the brakes in that situation may or may not have a problem... I don't think I've ever been able to lock the brakes on dry pavement with my enclosed trailer with the brakes setup reasonably well, though they certainly immediately started slowing my Dodge Ram 2500 Cummins (i.e. about 6k lbs + tow vehicle). At 20 mph and under it grabs hold even better and is not quite violent.

    Glazed shoes could do it... I'd be tempted to remove the shoes and scuff them with some rough grit sandpaper, as well as the brake surface of the drum.

    Mark

    snaponbob
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    11 Sep 2008 11:04 AM

    Jim, on most drum brake systems the shoe with the "long" pad goes to the rear so it is worth checking. And Mark is correct about possible glazing. Even new shoes may quickly glaze the initial contact arrears - happened to me! Sand them with some crocus cloth and sand the drum surface as well. I have mentioned the surface faces on the drums which in your case are TWO areas; the magnet contact area and brake shoe area. I fought the same battle and resolved with new drums.

    By the way, As I was addressing BOTH trailer brake issues AND tow vehicle rear brake issues I used your "keep plenty of space in front of me" method ------ until a person swapped lanes in front of me and suddenly slowed quickly. After a broken tab bracket on my van, damaged bumper skin on the rear of her car ($650 out of pocket), and a two point ticket for me I was forced to accept that the best laid plans often are flawed. The trailer is fixed, the van has a new proportioning valve, and the air packed ABS pump has been corrected. (I just KNEW that the shop that bled my brakes made it worse!!!).

    a911sc
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    11 Sep 2008 12:10 PM

    Jim,

    Drum brakes are self energizing so it's possible to adjust them too tight and they will not work as well.

    The shoes should only lightly drag the drum.  That's the way I've always adjusted drum brakes.  They need room to move.

    One other thing.  Do the shoes fit the drums?  You said the shoes are new, were the drum turned?  In other words if you put the shoes in the drum is the arc of the shoe the same as the arc of the drum.  If they differ slightly some amount of force will be wasted deforming the shoe to match the drum.   Or worse, only part of the shoe contacts the drum and braking force is lost.

    That's all I can think of right now.

     Paul Dornburg 

    Jim G
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    11 Sep 2008 03:28 PM

    Paul,

    Thanks for the ideas. I'm 99% certain these are the correct shoes but tonight I'll take the shoes off and lay them in the drum to see that they match. Drum wasn't turned btw.

    Bob,

    I recall laying the two shoes next to each other and they were identical. But I'll check tonight on that also.

    Mark,

    It's an enclosed trailer but it's tiny. Just barely big enough to squeeze my 900 lb car into it. And the roof is only about 5 and a half feet off the ground. Fully loaded = 4000 lbs. Empty and missing some tools, like right now, it weighs about 2500 lbs.

    Thanks everyone,

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