What Do the Trailer Brake Settings Actually Do?

[Rick3478]

So I understand the gain setting, no problem there, but what do the brake type settings actually do?
We have options like light electric, heavy electric, light electric over hydraulic, heavy electric over hydraulic.
The manual describes them by weight and type, but I want to know what the actual differences are between the settings, as in how does it behave differently. Attack and release rates are likely things that come to mind, but I don't find that in the manual. I hate when manuals try to pre-digest things. Some users may need that kind of hand-holding, but I'd prefer to know what's really going on. Anyone know the details?

 

[irishwake63]

I never could figure what elec over Hydraulic was I have a camper with what I thought were electric and thats the one I always used

 

[Rick3478]

Trailers with EOH have an electric actuator to apply hydraulic brakes. The electric control signal is still PWM, but instead of electromagnets moving the shoes or pads directly, you have hydraulics capable of a lot more braking force.

But it's unclear to me why the factory controller for our trucks has a different setting for it.

 

[Brutal_HO]

Primarily has to do with gain ramp rates and power level curves.

EOH pre-stages PWM signals to the pump to ensure there's pressure there when needed. Similar to how ACC/FCW will raise the line pressure in the ABS pump in the truck.



Best read you'll find on the internet re: RAM brake controller. Guy did an amazing job plotting it all out.

Brake Controller Troubleshooting/Technical Info

This post is about the brake controller on the 2021 HD Ram. First, my story. Second some reverse engineering and description of the warnings on the dash. Finally, some technical details. I would assume this information would apply to other years in the same generation of truck, but outside of...

hdrams.com

 

[Rick3478]

Primarily has to do with gain ramp rates and power level curves.

EOH pre-stages PWM signals to the pump to ensure there's pressure there when needed. Similar to how ACC/FCW will raise the line pressure in the ABS pump in the truck.

View attachment 184399

Best read you'll find on the internet re: RAM brake controller. Guy did an amazing job plotting it all out.

Brake Controller Troubleshooting/Technical Info

This post is about the brake controller on the 2021 HD Ram. First, my story. Second some reverse engineering and description of the warnings on the dash. Finally, some technical details. I would assume this information would apply to other years in the same generation of truck, but outside of...

hdrams.com

Thanks, that's exactly the kind of useful information I was looking for. This forum and the knowledgeable people in it are great!

 

[oe542bob]

Rick3478, I rarely use my dump or box trailers, but yesterday I needed to use my dump trailer. (5’X10’- 5000# single axle with electric brakes) After I connected it up, I noticed it had a trailer icon in yellow showing it was 30’. Also came up with something about the blind spot detection.
Then I when into the settings and picked “Dump” and the icon now showed the trailer as 20’.

 

[n8zcc]

So I understand the gain setting, no problem there, but what do the brake type settings actually do?
We have options like light electric, heavy electric, light electric over hydraulic, heavy electric over hydraulic.
The manual describes them by weight and type, but I want to know what the actual differences are between the settings, as in how does it behave differently. Attack and release rates are likely things that come to mind, but I don't find that in the manual.

I've wondered the same and looked at the PWM signals on the trailer brake circuit using an oscilloscope. The test was a 2015 RAM 3500 and a 2015 Montana 3790RD camper with electromagnetic brakes on both axles. After recording several braking events from different speeds using the various controller modes and comparing the scope results, I could not find any significant difference.

My 2015 owner's manual draws the line between heavy/light at a trailer weight of 10,000 pounds. My RV weighs in at 16,000 pounds but I leave it set at light electric and never experience an issue with this setting nor did I see a difference using heavy electric. I asked my dealer about it, they had no clue. I wrote RAM about it but never received a reply. I understand the graph posted above but I don't understand how RAM's brake controller behaves with respect to the modes.

As far as gain, it is a misleading term, gain is a percentage of the time the PWM signal spends providing power to the braking circuit. So lowering the gain reduces the PWM on time. A gain of 100% equates to 12 volts, and a gain of 50% equates to 6 volts, or in that proximity depending on the battery voltage level. Gain can not increase the value of the braking circuit above the battery voltage, only reduce it.

 

[Rick3478]

Rick3478, I rarely use my dump or box trailers, but yesterday I needed to use my dump trailer. (5’X10’- 5000# single axle with electric brakes) After I connected it up, I noticed it had a trailer icon in yellow showing it was 30’. Also came up with something about the blind spot detection.
Then I when into the settings and picked “Dump” and the icon now showed the trailer as 20’.

I think that's related to the trailer backing assist (probably not the correct nomenclature), which is a feature I don't have. My BigHorn has no idea what is behind it, just knows there is an electrical load on the trailer brake wire.

 

[Rick3478]

I've wondered the same and looked at the PWM signals on the trailer brake circuit using an oscilloscope. The test was a 2015 RAM 3500 and a 2015 Montana 3790RD camper with electromagnetic brakes on both axles. After recording several braking events from different speeds using the various controller modes and comparing the scope results, I could not find any significant difference.

My 2015 owner's manual draws the line between heavy/light at a trailer weight of 10,000 pounds. My RV weighs in at 16,000 pounds but I leave it set at light electric and never experience an issue with this setting nor did I see a difference using heavy electric. I asked my dealer about it, they had no clue. I wrote RAM about it but never received a reply. I understand the graph posted above but I don't understand how RAM's brake controller behaves with respect to the modes.

As far as gain, it is a misleading term, gain is a percentage of the time the PWM signal spends providing power to the braking circuit. So lowering the gain reduces the PWM on time. A gain of 100% equates to 12 volts, and a gain of 50% equates to 6 volts, or in that proximity depending on the battery voltage level. Gain can not increase the value of the braking circuit above the battery voltage, only reduce it.

The link above to the article in the HDRams forum has a lot more detail, and I recommend you have a look at that. And yes, move the decimal point on the "gain" setting, so 10.0 is a gain of one and everything else is less.

 

[HSKR R/T]

I've wondered the same and looked at the PWM signals on the trailer brake circuit using an oscilloscope. The test was a 2015 RAM 3500 and a 2015 Montana 3790RD camper with electromagnetic brakes on both axles. After recording several braking events from different speeds using the various controller modes and comparing the scope results, I could not find any significant difference.

My 2015 owner's manual draws the line between heavy/light at a trailer weight of 10,000 pounds. My RV weighs in at 16,000 pounds but I leave it set at light electric and never experience an issue with this setting nor did I see a difference using heavy electric. I asked my dealer about it, they had no clue. I wrote RAM about it but never received a reply. I understand the graph posted above but I don't understand how RAM's brake controller behaves with respect to the modes.

As far as gain, it is a misleading term, gain is a percentage of the time the PWM signal spends providing power to the braking circuit. So lowering the gain reduces the PWM on time. A gain of 100% equates to 12 volts, and a gain of 50% equates to 6 volts, or in that proximity depending on the battery voltage level. Gain can not increase the value of the braking circuit above the battery voltage, only reduce it.

Gain isn't a misleading term when you understand how it's used. When used for brake controllers, it's much like when used in radio frequencies. It just relates to the controllers ability to translate your brake pedal position, and the vehicle power signal, into an electrical signal to the trailer brakes. You obviously will never want your trailer brakes to apply harder than your vehicle brakes, or it will cause the trailer brakes to lock up which isn't good.

 

[Brutal_HO]

Gain isn't a misleading term when you understand how it's used. When used for brake controllers, it's much like when used in radio frequencies. It just relates to the controllers ability to translate your brake pedal position, and the vehicle power signal, into an electrical signal to the trailer brakes. You obviously will never want your trailer brakes to apply harder than your vehicle brakes, or it will cause the trailer brakes to lock up which isn't good.

Um, actually, this is how to stop a bad sway condition.

 

[Brutal_HO]

I think that's related to the trailer backing assist (probably not the correct nomenclature), which is a feature I don't have. My BigHorn has no idea what is behind it, just knows there is an electrical load on the trailer brake wire.

It's the blind spot monitoring that detects the length. It is extended to the trailer and detects the length after you make a turn or 2.

It will also disable blind spot if you select 5th wheel when prompted. I lie to mine and say conventional and it kinda sorta works a little.

You can save different trailers and select them and it will set the gain to whatever you had saved.

 

[Brutal_HO]

I've wondered the same and looked at the PWM signals on the trailer brake circuit using an oscilloscope. The test was a 2015 RAM 3500 and a 2015 Montana 3790RD camper with electromagnetic brakes on both axles. After recording several braking events from different speeds using the various controller modes and comparing the scope results, I could not find any significant difference.

My 2015 owner's manual draws the line between heavy/light at a trailer weight of 10,000 pounds. My RV weighs in at 16,000 pounds but I leave it set at light electric and never experience an issue with this setting nor did I see a difference using heavy electric. I asked my dealer about it, they had no clue. I wrote RAM about it but never received a reply. I understand the graph posted above but I don't understand how RAM's brake controller behaves with respect to the modes.

As far as gain, it is a misleading term, gain is a percentage of the time the PWM signal spends providing power to the braking circuit. So lowering the gain reduces the PWM on time. A gain of 100% equates to 12 volts, and a gain of 50% equates to 6 volts, or in that proximity depending on the battery voltage level. Gain can not increase the value of the braking circuit above the battery voltage, only reduce it.

As the author of the thread indicated, you can get the PWM % value from the ITBM via OBD if you have the custom diagnostic PID's in your logging app of choice. OBDLink has a ton of ITBM PID to select from in the logging app.

With my 5th wheel, I have to run my controller around the halfway point and use the LE setting. HE was way to "grabby" as it ramps up so much faster.

 

[HSKR R/T]

Um, actually, this is how to stop a bad sway condition.

Using the manual brake switch for trailer. Yeah

 

[oe542bob]

I don’t have the trailer back up option.

 

[Brutal_HO]

I don’t have the trailer back up option.

Correct, which is why I replied to @Rick3478 it's the BSM that detects and sets the trailer length.

Rick3478, I rarely use my dump or box trailers, but yesterday I needed to use my dump trailer. (5’X10’- 5000# single axle with electric brakes) After I connected it up, I noticed it had a trailer icon in yellow showing it was 30’. Also came up with something about the blind spot detection.
Then I when into the settings and picked “Dump” and the icon now showed the trailer as 20’.

I think that's related to the trailer backing assist (probably not the correct nomenclature), which is a feature I don't have. My BigHorn has no idea what is behind it, just knows there is an electrical load on the trailer brake wire.

 

[Rick3478]

It's the blind spot monitoring that detects the length. It is extended to the trailer and detects the length after you make a turn or 2.

Blind spot, eh? That makes sense and I stand corrected. Knew it was one of the fancy options I don't have.

 

[n8zcc]

As the author of the thread indicated, you can get the PWM % value from the ITBM via OBD if you have the custom diagnostic PID's in your logging app of choice. OBDLink has a ton of ITBM PID to select from in the logging app.

With my 5th wheel, I have to run my controller around the halfway point and use the LE setting. HE was way to "grabby" as it ramps up so much faster.

I did view the brake controller's PIDs. As Reagan said, trust with verification. I was investigating an issue with the ITBM at the time, a very serious problem.

RAM seemed to have an issue settling in on a brake control behavior. In 2013 MY they introduced a new brake controller, in 2014 MY, they introduced another brake controller. Then for 2015 (my year), they introduced yet another brake controller. This time, the brake controller's behavior was changed. What they changed was the amount of proportional PWM signal going to the trailer when braking. When the travel speed fell below 25 MPH, the brake controller pulled braking from the trailer. This can be very dangerous, think of a last-minute traffic light change and braking while towing a 16K RV. The truck's service brakes did the best they could and fortunately for me, there was no intersection cross traffic.

I and many others experienced the same issue and after several months of battling with RAM, they released a software update (November of 2015), the update included the ITBM, ABS, and stability control module. The sudden loss of braking below 25 MPH was corrected.

For my model year, the difference between heavy or light doesn't have a noticeable impact on the PWM signal of the braking circuit as observed on an oscilloscope. Sounds like this has changed over the model years.

 

[n8zcc]

Gain isn't a misleading term when you understand how it's used. When used for brake controllers, it's much like when used in radio frequencies. It just relates to the controllers ability to translate your brake pedal position, and the vehicle power signal, into an electrical signal to the trailer brakes. You obviously will never want your trailer brakes to apply harder than your vehicle brakes, or it will cause the trailer brakes to lock up which isn't good.

The definition of "gain" may be subjective in this context. Let's define what the "gain" setting does. When you set the gain of the trailer brake controller, you are setting the maximum amount of proportional braking provided to the trailer. If you set the gain to half, the PWM signal will never be more than 50% on (or half of the battery voltage) during the PWM period. There is one exception to this, manually controlling the brake controller. On both my RAMs, a 2022 and a 2015, and an aftermarket Prodigy, regardless of my gain setting, the brake controller's slide will apply 100% to the trailer brakes.

 

[oe542bob]

Today I took my box trailer to the manufacturer in PA. It’s a Low Hauler Haulmark that has a box length of 18’. Overall length is around 23’.
During the trip of 50 miles each way, I saw the “trailer icon” show 3 different lengths. Check out the pics.