Brakes appear uneven

TresK3 · September 21

I have a 2019 Tab 400 Boondock. It’s on its third set of tires and second set of brakes. Had the brakes done last spring. Late last year, I noticed that the brakes heated up unevenly when stopping. If I touched the left side drum it could get pretty warm (depending on how hard/long we’d been braking); hot enough that I didn’t want to hold my hand there for more than a second or two. On the right side, the drum would be barely warm.

I took it to a local trailer repair shop, who said everything looked good. They claimed that they adjusted the brakes, which I have no reason to doubt. However, the temperature difference remained. The trailer is now in my back driveway, jacked up so the wheels will spin free. If I spin the left wheel (the hot one) and apply the brakes with the controller turned all the way up, it locks right up. If I do the same to the right side, the wheel stops spinning (clearly the brakes are being applied, somewhat), but not nearly as quickly as the left side. If I take the brake controller down to a more typical level for my driving, it’s hard to tell an obvious difference in how quickly the wheels stop spinning - but that’s just with spinning the wheel by hand and no load on the tires.

I’ve looked at the wiring and don’t notice anything frayed or pulled out. My next step is to pull the drums and look at the brakes themselves. I have one wheel off, but I can’t get the drum off. I’m hesitant to bang on it too much, since I don’t want to have to replace the drum and I’m not sure how that would affect the bearings. Should I go rent a puller, or is there a trick to this?

Also… any thoughts on why the brakes seem uneven? It’s mostly noticeable after significant braking or if I have the controller at a higher setting.

How concerned would you be? The only real difference I notice is temperature. The trailer seems to handle and stop fine on the road.

Oh… and a final question. My son, who’s helping, suggested tripping the emergency brake wire to see if both sides lock up equally under those conditions. We tried tugging on the wire but did not get it to trip. Should we try this? If so, how difficult is it to reset the emergency system?

Thanks!

pthomas745 · September 21

The emergency break away brake only works if the trailer battery switch is on. So, check that item and maybe you can test the break away brake again.

You can have a look at your brake adjustment yourself. These are really pretty simple setups. The thread below has a description of "how to adjust", and also plenty of info on other things that might be happening inside the brake itself.

https://tab-rv.vanillacommunity.com/discussion/comment/75348/

vhollow · September 21

On my 400 the emergency break-away brakes are wired to the 12 volt side of the converter, so the battery needs to be on, as noted above, or the trailer needs to be plugged in to shore power for the brakes to activate. Pulling the break-away plug, attached to the steel cable, is difficult, if it hasn’t been done regularly or greased when checked. I used vice grips to spread the force where the cable attaches to a black plastic ring and still scraped my forearm on the frame the first time I checked this. Regarding drum removal, the star adjuster should be backed off pretty much all of the way to allow enough play between shoes and drums for removal. Conversely, when adjusting the brake shoes, the adjuster should be tightened until the wheel doesn’t turn, then backed off until there is still a little bit of drag.
This manual explains the process, and is a very handy resource for Dexter electric brakes:
https://www.dextergroup.com/user_area/content_media/raw/LDServiceOnline.pdf

swiftwave · September 21

Is it possible that different lengths of electrical wire to each brake results in a voltage drop on the longer wire, thereby reducing brake effectiveness on that side?

tabiphile · September 22

swiftwave said:

Is it possible that different lengths of electrical wire to each brake results in a voltage drop on the longer wire, thereby reducing brake effectiveness on that side?

Once the longer wire fills with electrons, the difference in length is equalized and the brakes will then work identically.

tabiphile · September 22

@TresK3, it would be interesting to learn mileage if it is known. You have seemingly gone through quite a few tires and brakes on a 6 year old rig.
From my perspective, I would be keen on making sure that the parts (drums, pads, springs) are all good and also lean towards making sure that the actual adjustment of the clearances is done carefully. Even when a brake adjustment is done by a shop, the degree of care and precision can vary greatly. It is very likely that one wheel has always been set a bit more tightly (less clearance} than the other. That will result in uneven braking and wear and also a difference in how warm they get when they are used. And....brakes are not super precise parts so it is possible (likely) that in order to get both wheels to spin freely, the tech may have had to adjust one looser than the other. If this was my Bdock, I would pull both wheels and have a look at things. As has been suggested, to pull the hub, you must back off the adjusters. Use a proper brake spoon to do this. A screwdriver can damage the soft metal adjuster. When the adjuster is loose, the hub should come off. If the hub has worn significantly you may need to use a puller or beat it loose with a hammer, hopefully not, but possible.
After assessing the parts, you should carefully reassemble taking particular care to adjust both sides equally. It is during this adjustment that you will learn if the sides are the same. It has been my experience with trailers and cars that it is rare for two wheels to "feel" exactly alike. If you know that one side has a tendency to run hot, run it a bit more loosely and snug up a touch on the other side to offset it. Then tow and see what you get. The tighter side (don't overtighten it) will turn, and break in with a closer clearance and may run a bit warmer. Then other side should run cooler. As long as the rig stops well and feels safe when you are towing you are good to go.
Brakes are not an exact science. There is a bit of mechanics "feel" to setting them up.
It is worth mentioning, if you have been through that many tires, the bearings and hubs on your Tab should be repacked and possibly replaced while this brake job is being done. Be certain that you are taking a look at those and also that the castellated nut has been properly adjusted to insure that the bearing races are correctly pre-loaded.

vhollow · September 22

Great suggestions from Tabiphile! Also, it might be helpful to measure amperage to the magnets, applying the brakes (gently, but consistently) with the hubs off. If the two sides are different, due to an abraded wire or other problem, breaking force would be applied differently to the two sides.

rfuss928 · September 22

tabiphile said:
Once the longer wire fills with electrons, the difference in length is equalized and the brakes will then work identically.

This is incorrect. These brakes draw several amps and the longer wire will have more voltage drop thus the solenoid will have less voltage available resulting in less power.
It seems the mechanical differences are excessive compared to typical experience. I agree that you have gone through quite a few tires and brakes on a 6 year old trailer.
Voltage measurements at each solenoid will full power applied would clarify that issue and help direct further trouble shooting.

Grumpy_G · September 22

tabiphile said:

swiftwave said:

Is it possible that different lengths of electrical wire to each brake results in a voltage drop on the longer wire, thereby reducing brake effectiveness on that side?

Once the longer wire fills with electrons, the difference in length is equalized and the brakes will then work identically.

But what if the electrons encounter obstacles and some of them expire in a hot fury ?

Joking aside, if there is resistance in the wiring it will reduce the voltage and ultimately the magnetic pull. There are some wiring junctions which can corrode and increase resistance. I would use a clamp ammeter to compare the two sides but I'll concede not everybody has one.

tabiphile · September 22

Grumpy_G said:

tabiphile said:

swiftwave said:

Is it possible that different lengths of electrical wire to each brake results in a voltage drop on the longer wire, thereby reducing brake effectiveness on that side?

Once the longer wire fills with electrons, the difference in length is equalized and the brakes will then work identically.

But what if the electrons encounter obstacles and some of them expire in a hot fury ?

Joking aside, if there is resistance in the wiring it will reduce the voltage and ultimately the magnetic pull. There are some wiring junctions which can corrode and increase resistance. I would use a clamp ammeter to compare the two sides but I'll concede not everybody has one.

Good input as with @r@rfuss928 observations.... The wiring should not be overlooked. Although these are simple brakes, every component needs to be working correctly.

The number of expiring electrons will be inversely proportional to their resistance to the furiousness..... there are specific reasons why my academic career in electronics was limited and included several small fires in lab.

rfuss928 · September 22

Guessing from afar with no data...
I suspect a bad connection for the weak brake. Voltage checks will help confirm and locate that.
I also suspect trailer brake overuse based on the excessive tire and brake shoe wear. This would exaggerate the differences in wear caused by braking the trailer and some of the TV.
No accusations here, just trying to troubleshoot an unusual situation.

TresK3 · September 23

Wow… thanks to everyone for good thoughts and links.

Several people mentioned the number of tires and brakes this trailer has had. I don’t feel anything is excessive there. The first owner of our trailer was @Verna, who I believe full-timed in it. Those original tires had maybe 50K on them when I replaced them. The second set only got about 20K before I noticed a issues and bought the third set (see my recent post about tires). I would like to have seen more miles, but there it is. The third set just went on and only has about 1000 miles on them. These are radials, so we’ll see if they do any better.

The first set of brakes were original. They were at about 60K miles when I had them replaced. The second (current) set of brakes has around 5 - 10K miles. These are the ones that are heating differently on the two sides.

Sounds like I need to have the battery “on” to test the emergency break-away brakes. Does this mean I have to have the battery on when driving? (If the trailer breaks free, it won’t have power from the tow vehicle to cause the brakes to work…)

Good links to adjusting. The trailer place I took it to recently seems competent, but you never know. They claimed the brakes looked really good and that they adjusted both sides. I will back off the adjusters and try to remove the drums. If they don’t come right off, I will get a puller. Then I can look at the brakes myself.

My personal thought, at the moment, is that the sides are getting different signal strength from the controller. I don’t have a clamp ammeter, just a basic multi-meter; is there a place to attach my leads, once I have the drum off?

And maybe it is just angry electrons on one side… perhaps I should pipe some calming music into the brake drums to help them relax.

manyman297 · September 23

I’m currently dealing with a mystery brake condition…months long battle that I won’t bore you with. But I’ve learned a lot.

People struggle with removing the drums but fail to realize they just need to back off the star wheel adjustment a few clicks. Slides off smoothly. You’ll need to readjust the brakes anyway after you put the drum on so loosening the star wheel is no biggie.

Invest in a decent temp gun. $15-25. This will give you numbers to go off of instead of feeling. Way worth the investment.

The only way I know of to test voltage is to try and gain access where the magnet leads attach to the trailer wiring (probably using butt connectors). If there’s room you can attach your voltmeter leads there. Otherwise you may have to remove a bit of the jacket on the wiring. Just use some liquid electric tape to seal it back up.

I had an issue a few years back on our 400 similar to yours. Adjust the drums properly. Start from there and you might have to adjust each wheel independently to get them braking evenly. It’s frustrating l know. In fact brakes have been the #1 issue with our trailer. They suck.

rfuss928 · September 23

manyman297 said:

The only way I know of to test voltage is to try and gain access where the magnet leads attach to the trailer wiring (probably using butt connectors). If there’s room you can attach your voltmeter leads there. Otherwise you may have to remove a bit of the jacket on the wiring. Just use some liquid electric tape to seal it back up.

There are needle probes available for voltmeters but a straight pin piercing the insulation will do the job. A little liquid tape wouldn't hurt after the piercing but it isn't always necessary depending on the environment.

TresK3 · September 27

@rfuss928 - I’m going to poke a couple of pins into the wires going into the brakes, that way I won’t have to take the drums off to measure DC voltage. Or do I want to measure DC current? I assume voltage, but will it matter?

rfuss928 · September 27

TresK3 said:

@rfuss928 - I’m going to poke a couple of pins into the wires going into the brakes, that way I won’t have to take the drums off to measure DC voltage. Or do I want to measure DC current? I assume voltage, but will it matter?

Voltage is perfect. Get as close to each backing plate as practical. You're hoping to get close to each solenoid and see the voltage that is reaching them. You should see the greatest voltage difference at maximum braking. Make your ground connection on each backing plate for the best indication.
Good luck...
If you have an amp clamp type meter, I would take current readings on each side also while you're there.

TresK3 · September 28

Put safety pins into the wires going into the brakes (two wires on each side) and measured the voltage under varying conditions. I’m not sure how close the voltages should be.

1st observation: Using the manual override button on the Prodigy RF controller unit in the car gave higher readings than pressing on the brake pedal, regardless of which side I was testing. However, trying to turn the hubs by hand felt about the same whether we used the brake pedal or the manual override (admittedly a pretty inaccurate measure).

Using the manual override, with the Power Knob set to it’s highest, I got 11 volts on the left side (the one that seems to brake more) and 9 volts on the right side. If we just use the brake pedal in the car, that drops to 3.3 volts on both sides.

If I turn the Power Knob down about 1/2 way (our typical setting, when driving) then the Manual Override gives 7.2 V (left) and 5.47V (right). However, if we use the brake pedal those numbers even out to 1.7 V (left) and 1.45 V (right).

Is it significant that the Manual Override gives much higher voltages than using the brake pedal? Also, it took a second or two for the voltage to come up fully (and to hear the slight hum of the solenoid); I assume that is normal.

The difference between left and right, when using the brake pedal and having the controller set at about halfway was 0.25V, which works out to about 15%. That doesn’t seem like a lot to me, but I’m not sure how close they should be.

Conclusions: Both sides are getting voltage. The right side gets a little less voltage than the left, but not hugely different under “typical” conditions. The only major difference was when the controller was set half-way and we used that to apply the brakes (7.2 vs 5.47 V).

Any more thoughts, anyone?

TresK3 · September 28

Also… I still can’t get the drums off. I tried backing off the adjuster nut all the way; the drum turns freely (I can hear something rubbing a little) but it won’t come off. I used some penetrating oil on the studs for the lug nuts and banged a bit with a rubber mallet, but nothing is happening. Based on experience with other brakes, it shouldn’t be that hard.

Grumpy_G · September 28

Sounds like you're expecting the drums to come off like on a 70s-80s rear wheel drive car. They won't, the hub and drum are a single piece and you need to remove the wheel bearing to get the drum off.

Horigan · September 29

@TresK3
Some controllers measure deceleration to determine voltage to the brakes when the brake pedal is applied. At least mine does. There is a switch on the brake pedal to enable this control. The controller doesn't measure brake pedal pressure. This is likely why the voltage is lower verses when you use the manual lever. I would measure the voltage at the tow vehicle connector via the manual lever, just to see what voltage is getting to the trailer. You obviously have excessive voltage drop (resistance) on the wires to the right brake. I suspect the brake wires split at the junction box behind the spare tire. Maybe you have a bad connection in the junction box.

TresK3 · October 5

@Grumpy_G - Precisely; I did expect them to pull off like my old Honda, and my old Pinto, and my old LTD Station wagon, and my old… my, I AM old.

As this is the case, I won’t try to dig into them any further, but just play with adjustments and try to get the two sides even, while the are jacked up.

Maxcamp · October 6

@Horigan writes:
You obviously have excessive voltage drop (resistance) on the wires to the right brake. I suspect the brake wires split at the junction box behind the spare tire. Maybe you have a bad connection in the junction box.

On our 2021, Nucamp ran one 10awg wire from the junction box to the driver side brake. They used T-tap connectors to then run laterally across the axle (with ONE tywrap securement) to the passenger side brake. Thus setting up different electrical resistance to the two brakes. We were forced to rebuild the entire system after this wire failed.

https://tab-rv.vanillacommunity.com/discussion/17161/why-did-why-will-your-brakes-suddenly-fail-on-one-side-lifesafety-issue#latest

Horigan · October 6

Well there you go!

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