Brake Controls -
Howdy -
Had a fellow ask me how to adjust and use trailer brake controls and as we talked it came to me that he didn’t really know the difference between a timer control or a proportional unit or any of the other methods of trailer brake control so I figured I’d drop a few words about the subject. Now it sounds simple but as Sir Issac Newton proved, once you get a mass moving it wants to continue to travel until resistance finally slows it to a stop. The word to remember is “Inertia”. Our trailers are that mass behind us and once put into motion it they want to keep moving. So we live with the “Curse of the brake controller” when we tow. Of course none of us tail-draggers are pulling an overweight trailer so our tow vehicle should stop it just fine – right ? Sure, just like nobody plays computer games !! The federal government’s rules for towing say that the tow vehicle of any trailer is only responsible for the first 2,000-pounds of trailer weight. All trailers over 2,000-pounds require that a controlled braking system be installed.
Brake controllers have gone from a simple timing device to pendulums to the modern accelerometer driven devices most of us use today. The overriding theory has always been that you want your trailer brakes to engage at precisely, or slightly ahead, of the tow-vehicle’s brakes. The trick is how to accomplish the proper timing. If the tow vehicle begins stopping before the trailer you have an instant case of “Tail wagging the Dog”. If the trailer brakes lock-up or begin grabbing then you have tire wear and unsafe braking, not to mention the “bobble-head” effect to the driver and passengers. Every manufacturer has had to fall back on the one common event that occurs every time a tow vehicle’s brakes are applied and that’s stepping on the tow vehicles brake peddle.
Your car or truck’s brake light comes on the moment the brake pedal is pushed. The light signal is slightly before any brake pressure is actually applied thereby giving the trailer brake controller a bit of a head start in the stopping process. Brake control manufacturers take advantage of this by tapping into brake light wire and sending a small amount of power to the trailer brakes the moment it’s detected. That’s how your trailer stops “ahead” of the tow vehicle. An alternative is a cable link from the brake pedal to the controllers, again to detect movement of the pedal.
All brake controllers are a compromise in function. The smarter the controller the better, but the driver may still have to “tune” the controller to fit the conditions. To have smooth stopping at slow speed we want the tow vehicle to do most of the stopping and have just enough brakes on the trailer to keep is straight and assist in slowing down. In an emergency we want the trailer brakes to be much more aggressive. On most brake controllers, the driver adjusts this initial power output with the GAIN control. That way, the power can be reduced in city driving to keep the trailer brakes from “grabbing”. The safety issue here is that the driver can fail to turn the gain back up for high-speed driving, which can result in an accident in a panic stop situation or the driver sets the gain to high which makes the trailer try to stop the tow vehicle. Now having said all this, the biggest fly in the ointment is often the driver over “adjusting” the controller instead of letting it do it’s job.
Since all current controllers are operated by the brake light signal or a strain-gage cable running from the brake peddle to the controller to make them function the biggest differences is in how the power is metered to the brakes. Time-controlled systems use Gain and Timer settings. These controllers don’t care about the outside world, only how much gain, or power, to apply and over how much time to apply that gain. Strain-gage and cable type controllers are essentially doing the same thing, except they detect the slight “tug” on the cable instead of brakes light power to detect brake pedal movement.
Now I know that some of you, er, more senior folks are going to brag about the “master cylinder tap” along with your uniquely tuned resistance coil. In this setup the controller was directly connected to the tow vehicle’s master brake cylinder and pressure from the cylinder was what determined the voltage from the controller. A resistance coil was used to “smooth” the power output and keep the controller from dumping all the power directly into the trailer brakes. The advent of ABS or anti-locking brake systems did away with this type of system because the ABS unit can mis-read braking conditions if a controller is directly attached to it.
Smarter systems use a pendulum to measure braking Inertia from the tow vehicle’s slowing down. During normal braking in town there isn’t much inertia so the controller only puts a small amount of voltage to the trailer brakes. However radical braking, such as a panic stop, forces more rapid movement of the pendulum and more power is applied to the trailer’s brakes. There is a set-up procedure that includes leveling the unit’s pendulum and setting the gain control, but this is easily done, and unless ya monkey with it it doesn’t need to be done again.
We live in a computer age and the top of the line systems use accelerometers that “sense” movement of the towing vehicle. Their computer-driver brains automatically adjust to real world conditions and compensate for them. You can even set the amount of power and time advance that the controller provides to the brakes. Once the accelerometer or other input device takes over, the power sent to the brakes depends on two factors: the reading from the input device and the gain set by the driver. In the case of an accelerometer based controller, the deceleration of the tow-vehicle is measured and, depending how rapidly the tow-vehicle is slowing, power is sent to the trailer brakes. Again, this output is limited by the gain setting. This is true of any brake controller, whether it taps into the brake line, brake lights, cables to the brake pedal, or uses an accelerometer to control power to the trailer brakes. In accordance with federal law all brake controllers have a over-ride system that suspends the normal controller function and applies power immediately to the trailer brakes, but with most controllers this is limited by the amount of total power the gain control is set for.
One of the best solutions to all the problems of trailer braking is the electric/hydraulic disc brakes for the trailer. In this system the trailer has automotive disk brakes installed. These brakes are hydraulically operated, just like on a car but instead of a vacuum booster an electric motor operates a hydraulic pump mounted in the trailer which provides the pressure to the disk brakes. Hydraulic brakes, however, have their own problems, the biggest being the slight delay which can be as much as a half second between pressing the brake pedal and the activation of the hydraulic actuator. Ironically, the best brake controllers for this type of system have always been the low cost timer or pendulum based controllers, which don’t allow for all conditions and are still limited by the gain setting.
The goal of any of these controllers is to make the trailer brakes work in conjunction with the tow-vehicle brakes under all the conditions we find on the open road. Easy? No! Always remember, the biggest factor in trailer brake control is still the nut holding the steering wheel !
Latter – -
The Old Ranger
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nice job!
Very interesting, any brands or models of brake controllers you can recommend.
good reading . better understanding on funtions of brake controller
I am in the process of upgrading from a Tekonsha Voyageur to a Tekonsha Prodigy..I am told that I can do it myself as the conversion is just a matter of switching wiring looms??? is that right…….I really dont want to do this myself unless its an easy move..
[...] different responses from the controller than that encountered on the open road. A good read: Brake Controls – | blog.rv.net – The Official Blog of the Open Road Red __________________ Ralph Featherstone Silverdale, Washington 2005 Titan KC SE, Helwig, [...]
Why no mention of the Ford and Chevorlet factory installed systems?
I have a real problem finding a brake controller that works with my electro/hydraulic disk brakes. I have the BrakeRite actuator and Kodiak disk brakes. The actuator requires 26A to exert 1500 psi. and about 13A for 500 psi. The BrakeSmart controller that I presently have does not do the job. The hydraulic sensor is not sensitive enough to send an adequate signal to the actuator to even slow my trailer down at reasonable petal pressure. The actuator requires about 60% of total output to start braking my 16,000 lb 5er. At present, I know of no controller that will work.
Howdy Elmer !
The timer units from Cequent Towing Group seem to have had the best results. Kodiak used to supply a unit of their own, have they stopped doiing this ? Mac McCoy (The fire Guy) had one of the prototype Kodiak units on one of his 5th wheel’s back in the 90’s so you might drop him a line – he’s on the BLOG here – and see what he used.
I’ve got a couple of contacts to check with for you – so I’ll get back to you – -
Mike
We just got a 24 ft camper and need to install a brake control system. The camper is already been updated for the electric brakes. What is the best control box to have? There are just so many of the them. Some a very cheap and others expensive. I am a mechanic and union millwright but I have never hooked one of these up. I know how to use them because I had to borrow a truck before that had a control box. The ones I have seen on the web, ebay,,,look like they are just plug to plug. Can anyone tell me what to go with cheap or expensive. What does the job?
You get what yu pay for………..get something mid range that will do the job for a few years…..
The Tekonsha P3 is a new brake controller that works with both electric and electric-over-hydraulic brakes. I’m having one installed tomorrow!
http://www.tekonsha.com/p3.html
Howdy Rick !
Yep, the P-3 is a super controller – I did a product test on one last fall but I didn’t have access to a trailer with electric-over-hydaulic brakes. I’d like to have you input after you get some time on the system if you would please. What disk brake system do you have and how do you like it.
Thanks for the input !!
Mike
Great read Mike, havn’t done any RV ing since 74 well not big rigs anyway. This was a great reminder although I got her home OK I did have to do some fine tuning , yup and you can forget to turn the juice up when you get out of town. Gonna have to make me a note and post it on the dash
Thanks Slink
Mike,
I had a question about tow vehicles and Lynn Difley suggested I ask you.
My question, being new to RVing, is where can I find information on towing a vehicle behind a DP motorhome. I would like to know what vehicles can be towed with all 4 wheels on the ground? I’ve heard that some makes can be towed without major alterations. Thanks for your help,
Steve Vollmer
Thanks so much for the information. We have been RVing for many years with a small Class C, towing motorcycles and therefore haven’t required a braking system. We have just purchased a 1995 Beaver DP, 33 ft long and plan to tow a 2007 Ford Ranger (2-wheel drive) and therefore we now need a braking system. We were looking at an EvenBrake system sold at Camping World. Any thoughts on whether this is a good system or whether we should look at something else? Thanks for any suggestions you might have.
I need some info on ‘installing’ a prodigy controller. My first unit was installed a little higher than horizontal. We experienced sporadic braking. I felt it was defective and returned it fo a new one which I have not installed yet. So, after viewing their video over and over – it appears the unit shown is more in a vertical install not horizontal as my last 2 were (before Prodigy). I have a 01 Dodge Ram 2500.
So, if anyone can clarify the install angle I would be most appreciative – we wnat to get on the road, well, soon
Thanks,
Jim
Howdy !
Reckon it’s time to catch up on this thread – first the towing behind a motorhome issue. Most cars can be “flat towed”, that is, with all wheels on the ground. Check your vehicle manual and it should tell you. Motorhome magazine puts out a towing guide every year with all the vehicles it’s possible to tow so check that out also.
Now, why didn’t I mention the Ford and Chevy built-in brake controllers? Reckon that I just wasn’t thinking abut them at the time! The Ford unit is a Prodigy unit that Ford linked into the chassis computer so it could read the transmission. Nice setup ! The Chevy unit is an in-house system build using some of the Tekonsha tech. Again a nice unit.
Now for the last question. The Prodigy does not care how you mount it. The spec’s call for it to be within reach of the driver’s hand to use the override and that’s about it. It uses a solid state accelerometer, not a swinging mass sensor so the angle of the unit can be almost anywhere so long as the critter isn’t mounted sideways !
Normally I get all the notes that folks leave on the BLOGs but for some reason these didn’t get to me until Jim’s came in and I looked. Anyway, hope this helped and iffen I can assist or whatever just drop me a line here.
Later – -
Mike – The Old Ranger – Steffen
Dear friends of the towing world,
I have read, with keen interest, and digested all the interesting things written and suggested by all the participants relating to the trailer towing fraternity. I have a question; this posed by someone who insists that there has got to be another way that the braking efficiency control of a trailer’s brakes can be achieved; this without the installation of automatic -cum-manually calibrated equipment on the towing vehicle. He feels that the equipment fitted in and on the towing vehicle is awkward, clumsy, unattractive, inefficient and a poor show for the times of super-advanced Hi-Tech achievement in which we are now living. I personally believe there is no other way to control the trailer braking under varying loads and conditions: but who knows; maybe his question is worthy of some serious. brainstorming. I would appreciate some feedback, whether positive or negative; just so that I can go back to my friend with answers or comments that do not only come from me.
Kindest Regards.
Terry Roe.
Cape Town, South Africa.