32 foot TT, about 7000 pounds plus our gear and stuff:I've noticed the brakes are underperforming substantially. Got the gain on the Prodigy turned all the way up, when I grab the lever and throw max voltage at the brakes, all it does is slow the thing down a little. I'd say maybe 20 percent efficiency at best.Not good enough, time to open it up.I've been wrenching my own vehicles since I was a teenager, I rebuild engines, trannies and every other aspect of cars and pickups, therefore I know what I'm doing with mechanical things.I've been doing brake jobs all my driving life.However, I have never had trailer brakes apart.I'm wondering, do most trailers have a similar adjustment technique as the old drum brakes on the old 60s and 70s cars? Where you pull off the little rubber cap on the backing plate and get in there with a brake tool or bent screwdriver?Weak brakes, could they just be suffering from bad need of adjusting?Are they self adjusting like the old cars or do we have to get after them once in a while?Just thought of this now, but suppose I should get under there, probe the wires and make sure I have voltage at the hubs....Should be able to lock the wheels up with full on braking. Not so here...Tips and tricks for getting my brakes in order? Best method to check each wheel?Guess I should pull the drums and have a peek anyways.Long trip coming up soon, gotta take care of this before departure. TT is 12 years old, maybe it needs shoes.

It is very likely that they do need adjustment. They significantly loose mechanical advantage between the actuation magnet and the shoes when they have too much clearance. They adjust exactly like you say. I recommend replacing the bearing seals while you are in there. It's pretty easy work but quite messy.

Trailer brakes are actuated by magnets dragging on the inside of the brake drum. The amount of force can be measured with an ampmeter. The draw for fully applied brakes is a little over 3 amps per brake. You can add an ampmeter in series with the wire from the controller on your dash to the brakes on the trailer. There should be a leveler on the controller that allows you to manually apply the brakes.Some are self adjusting and many are not. They can be adjusted with a standard spoon from the days when brake drums were used. You'd need to pull the drum to see what you have. Take measurements of the width of the shoes and the diameter of the drums as well as checking to see if they're self adjusting while you're looking. The brake shoes and magnets do wear out and need replacing. The easiest way to do that is to replace the whole backing plate. That gives you new shoes, magnets and all new hardware.There's lots of information here as well as decent prices:https://www.easternmarine.com/trailer-brakeshttps://www.easternmarine.com/electric-trailer-brake-assemblies

Bob,I've been to your movie.I replaced the backing plate, adjusted the brakes, replaced the magnets, replaced the controller... Still no real breakingLong story short. Check the wear on the inside of your drums. My prior controller must have been sending some power to the magnets, they dragged and wore down all four drums inside face where the studs are pressed into the drum. the magnets were shot and when I replaced them, they wore into the shape of the drum eventually (about 1000 miles worth of driving).The surfaces worn down concave (convex? I never remember which is which) to the point where the brakes didn't work enough to really stop the trailer.Ultimately, I replaced the axles because it was about the same price as getting new drums and backing plates, and magnets - and they had a higher weight limit (6,000 versus 4,400 each axle).PM me if you've got questions.josh

Bob,Trailer brakes easier then buttered furnace duct.Yes trailer drum brakes just like days of old except electric/magnet actuating shoes vs hydraulic slave cylinder12 yrs old.......it time for some new shoes and internalsBuy 2 right side and 2 left side backing plate assembliesBack the adjuster off...remove drumsDisconnect 2 wires to magnet..4 bolts and old backing plates come offNew inner/outer bearings/sealsAfternoon job...one side at a time/one wheel at a time

Yes you should certainly adjust the brakes at 12 years. Actually 12 months or 12,000 miles would be OK also. OK to repack the bearings at this point too.Yes they adjust same as all other drum brakes.A few are forward self adjusting but I assume yours are not. When you pull them apart you will see a familiar cable and adjuster if you have this option.Some lock up and others do not but you should get very significant braking force when full power is applied manually. Although I found after sitting in storage the initial braking was a bit less until you make 5 or 10 stops to get them worked in a bit.Best electrical check is a clamp-on DC ammeter reading. At full power you should see about 3 amps through each coil. More and you have a short, less and you have a bad connection.Shoes last a long time with mostly highway miles. The material seems thinner than a vehicle so unless it is very thin I would keep running them.Keep us updated with what you find. Post a picture if something does not look right.

Trailer brakes weak, a few questions: | Good Sam Community

26 Replies

jfkmk
Explorer
Jul 24, 2019
As mentioned, working on trailer brakes is aa simple as it gets, especially for someone who works on cars. Repack the bearongs too.
time2roll
Nomad
Jul 24, 2019
Yes you should certainly adjust the brakes at 12 years. Actually 12 months or 12,000 miles would be OK also. OK to repack the bearings at this point too.

Yes they adjust same as all other drum brakes.

A few are forward self adjusting but I assume yours are not. When you pull them apart you will see a familiar cable and adjuster if you have this option.

Some lock up and others do not but you should get very significant braking force when full power is applied manually. Although I found after sitting in storage the initial braking was a bit less until you make 5 or 10 stops to get them worked in a bit.

Best electrical check is a clamp-on DC ammeter reading. At full power you should see about 3 amps through each coil. More and you have a short, less and you have a bad connection.

Shoes last a long time with mostly highway miles. The material seems thinner than a vehicle so unless it is very thin I would keep running them.

Keep us updated with what you find. Post a picture if something does not look right.
Old-Biscuit
Explorer III
Jul 24, 2019
Bob,
Trailer brakes easier then buttered furnace duct.

Yes trailer drum brakes just like days of old except electric/magnet actuating shoes vs hydraulic slave cylinder

12 yrs old.......it time for some new shoes and internals
Buy 2 right side and 2 left side backing plate assemblies
Back the adjuster off...remove drums
Disconnect 2 wires to magnet..4 bolts and old backing plates come off

New inner/outer bearings/seals

Afternoon job...one side at a time/one wheel at a time
jodeb720
Explorer
Jul 24, 2019
Bob,

I've been to your movie.
I replaced the backing plate, adjusted the brakes, replaced the magnets, replaced the controller... Still no real breaking

Long story short. Check the wear on the inside of your drums. My prior controller must have been sending some power to the magnets, they dragged and wore down all four drums inside face where the studs are pressed into the drum. the magnets were shot and when I replaced them, they wore into the shape of the drum eventually (about 1000 miles worth of driving).

The surfaces worn down concave (convex? I never remember which is which) to the point where the brakes didn't work enough to really stop the trailer.

Ultimately, I replaced the axles because it was about the same price as getting new drums and backing plates, and magnets - and they had a higher weight limit (6,000 versus 4,400 each axle).

PM me if you've got questions.

josh
DFord
Explorer
Jul 24, 2019
Trailer brakes are actuated by magnets dragging on the inside of the brake drum. The amount of force can be measured with an ampmeter. The draw for fully applied brakes is a little over 3 amps per brake. You can add an ampmeter in series with the wire from the controller on your dash to the brakes on the trailer. There should be a leveler on the controller that allows you to manually apply the brakes.

Some are self adjusting and many are not. They can be adjusted with a standard spoon from the days when brake drums were used. You'd need to pull the drum to see what you have. Take measurements of the width of the shoes and the diameter of the drums as well as checking to see if they're self adjusting while you're looking.

The brake shoes and magnets do wear out and need replacing. The easiest way to do that is to replace the whole backing plate. That gives you new shoes, magnets and all new hardware.

There's lots of information here as well as decent prices:
https://www.easternmarine.com/trailer-brakes

https://www.easternmarine.com/electric-trailer-brake-assemblies
bartlettj
Explorer
Jul 24, 2019
It is very likely that they do need adjustment. They significantly loose mechanical advantage between the actuation magnet and the shoes when they have too much clearance. They adjust exactly like you say. I recommend replacing the bearing seals while you are in there. It's pretty easy work but quite messy.

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Trailer brakes weak, a few questions:

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