Uneven trailer braking - Fiberglass RV


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Old 01-29-2007, 10:51 AM   #1
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I have noticed for some time that the curb side wheel is generally warmer than the street side. This is most noticable when towing in urban traffic. The bearings are good and just inspected and repacked. The hubs, after towing for hours at interstate speeds without braking, are cool.

As an experiment, I connected the Scamp to the tug and applied the brake test slider to give 100% voltage to the brakes and towed the trailer down the driveway. The curb side locked (as I would expect) and left a skid mark down the drive... the road side did not. I jacked the trailer up and spun the road side wheel and had my wife apply the brakes. The wheel would stop spinning in about 1/4 turn and it was impossible for me to continue to rotate it (in other words, the electric brakes on the road side do function).

1. Is there any adjustment mechanism on the electric brakes (this was a PM item on older cars back in the '50's).

2. Other thoughts? The voltage has got to be the same as there is only one hot wire for both brakes).
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Old 01-29-2007, 11:23 AM   #2
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There is an adjustment on each side. The voltage to the magnets should be checked, as corrosion might affect the electrical pathway (or a wire might be disconnected). The moving parts should be checked, cleaned and lubricated. I would take it to a good brake shop. Depending on the condition of the brakes, it may be more economical to replace the backing plate with the whole brake mechanism.
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Old 01-29-2007, 11:47 AM   #3
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I have noticed for some time that the curb side wheel is generally warmer than the street side. This is most noticable when towing in urban traffic. The bearings are good and just inspected and repacked. The hubs, after towing for hours at interstate speeds without braking, are cool.

As an experiment, I connected the Scamp to the tug and applied the brake test slider to give 100% voltage to the brakes and towed the trailer down the driveway. The curb side locked (as I would expect) and left a skid mark down the drive... the road side did not. I jacked the trailer up and spun the road side wheel and had my wife apply the brakes. The wheel would stop spinning in about 1/4 turn and it was impossible for me to continue to rotate it (in other words, the electric brakes on the road side do function).

1. Is there any adjustment mechanism on the electric brakes (this was a PM item on older cars back in the '50's).

2. Other thoughts? The voltage has got to be the same as there is only one hot wire for both brakes).
When was the last time you adjusted the brakes or had them adjusted. I know the brakes on my 13' don't have automatic adjusters, so they require periodic manual adjustment.
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Old 01-29-2007, 01:12 PM   #4
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Mechanical brake adjustment at each wheel solved this problem for me when we first bought our used (new to us) Casita.
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Old 01-29-2007, 02:58 PM   #5
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The adjuster on the linkage for the brakes shoes is basically the same as any other drum brake. It is still there in modern cars, but has a little spring ratchet part to make them take out slack when applied in reverse; I don't think the trailer version has the ratchet, but I could be wrong. On my Boler, the dropped axle beam blocks any reasonable access to the small slot in the backing plate which allows access to the adjuster.

I agree that the problem may be electrical. Since the brake magnets are connected in parallel, a broken (or just very high resistance) connection may affect only one side. If the resistance in the wiring to one side is much more than the other, brake current will be uneven; although they share the same supply wire, the wiring must split in two somewhere and the voltage at the magnets could be quite different. Normal resistance is less than 4 ohms per magnet for typical magnets (e.g. Dexter).

I had one-wheel braking when I first set up my Boler, and since it was due to a bad connection somewhere in wiring (zero volts on that side) it led to my complete brake system rewiring - I needed an excuse to fix that stuff up, anyway.
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Old 01-29-2007, 03:36 PM   #6
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Here's a link to download Dexter's complete Electric Brake Service PDF -- How they work, how to service/adjust, how to troubleshoot (including all the appropriate electrical results and how to measure them) -- A person would be hard-pressed to find a better service guide.

Dexter also has a separate Electric Brake Troubleshooting PDF, but all the info in it is in the PDF above, and more.

Anyone of any technical inclination whatsoever should go to the Dexteraxle.com site, click on Service Literature and download a few PDFs -- It's an incredible tech resource on both leaf spring and torsion axles and related equipment. Info is also available on the Al-Ko and Henschen sites.
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Old 01-29-2007, 03:52 PM   #7
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When I had one-wheel braking, I was surprised how little the trailer pulled to the side in full-effort brake testing... which means that a "stronger on one side" feel might really indicate "no braking at all on the other side". Definitely follow the Dexter guide, and check the street side wheel to see if that brake does anything at all (such as by the method already used for the curb side).

Good luck. Fortunately, electric brakes are so simple it is sure to be fixable.
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Old 01-31-2007, 08:46 AM   #8
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Here's a link to download Dexter's complete Electric Brake Service PDF -- How they work, how to service/adjust, how to troubleshoot (including all the appropriate electrical results and how to measure them) -- A person would be hard-pressed to find a better service guide.
Pete: thanks! This is exactly what I'm looking for. I'm not sure whether the axel is Dexter or some other mfg. as Scamp used two brands. I'm sure the adjustments and such are similar tho.

I'm fairly sure that the brakes havn't been adjusted in a long while... if ever.
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Old 01-31-2007, 08:33 PM   #9
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Even if it's an Al-Ko axle, they often use the Dexter components inside it -- They are the same as far as all this goes.
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Old 02-01-2007, 08:00 AM   #10
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There is an adjustment on each side. The voltage to the magnets should be checked, as corrosion might affect the electrical pathway (or a wire might be disconnected). The moving parts should be checked, cleaned and lubricated. I would take it to a good brake shop. Depending on the condition of the brakes, it may be more economical to replace the backing plate with the whole brake mechanism.
I donít know how Scamp attaches the wire from the magnets to the trailer but Casita uses Scotch Loks. When I had a similar problem, I discovered that the connections were corroded. Scotch Loks are not water proof and mine were filled with green oxidation and the copper wires had turned black up inside the insulation. A search of the Internet turned up some reasons why Scotch Locks should not be use in critical applications. Under a trailer where the wires are subject to water, salt and other nasty chemicals, a check of the connections should be part of your annual inspection.
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Old 02-01-2007, 09:54 AM   #11
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I donít know how Scamp attaches the wire from the magnets to the trailer but Casita uses Scotch Loks. When I had a similar problem, I discovered that the connections were corroded. Scotch Loks are not water proof and mine were filled with green oxidation and the copper wires had turned black up inside the insulation. A search of the Internet turned up some reasons why Scotch Locks should not be use in critical applications. Under a trailer where the wires are subject to water, salt and other nasty chemicals, a check of the connections should be part of your annual inspection.
Craig; I checked the wiring connections... they were connected using a barrel crimp connector and wrapped with electrical tape. While this wouldn't be my choice of connection, the tape appeared to be effective in preventing water from getting to the connection... they were dry and not corroded. I much prefer soldered connections with both the electrical tape and shrink tubing but in this application I assume they would need to be disconnected to replace/service the brakes.
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Old 02-01-2007, 10:50 AM   #12
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You haven't said whether or not you have inspected the brakes.

A leaking seal will put enough grease between the magnet and the drum to lower the braking action.

Also a little grease on the brake shoes themselves will cause a loss of braking on that wheel.
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Old 02-01-2007, 06:03 PM   #13
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... in this application I assume they would need to be disconnected to replace/service the brakes.
The wires would only need to be disconnected if the backing plates were removed (unlikely unless replacing every moving part) or if the magnets themselves need replacement. When the hub/drum is pulled off the brake shoes etc. are accessible, and the backing plate and wiring do not need to be touched.

It's just like the brake hose connection to an automotive drum brake assembly... it is never disconnected for service unless the slave cylinder itself (the hydraulic equivalent to the trailer magnet) is being rebuilt or replaced.

This is a good thing in my case, because I went a little overboard on sealing my brake wiring splice joints. They're just crimped splice connectors, but they're buried under multiple layers of shrink tubing etc.
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Old 02-01-2007, 06:19 PM   #14
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There's a product called "Liquid Electrician's Tape" that is sort of like neoprene cement (wet suit cement for you SCUBA divers), in fact, it may even be that stuf -- Comes in colors even! Just paint it on over a connection and it will seal it. Get the stuf from places like Home Depot. Or use neoprene cement if you have it (we used to use it on small boats in salt water and it did fine).

If I had questionable connections, I would get some new connectors (Scotchlocks would be OK), take off the old ones, clean the wires with rubbing alcohol, install the new connectors and paint everything generously with the liquid tape.

They also make connectors with silicone grease inside them, intended for buried connections, but if one uses the silicone grease, likely one will ALWAYS have to use same in that place because it is difficult to clean off and then have anything else stick to the cleaned surface...
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