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Old 08-13-2004, 06:53 AM   #1
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How Much Work do the Trailer Brakes Do?

I seem to be a font of dumb questions, but as a total newbie to this whole monster towing thing, I have to come up to speed as fast as I can. I have until November 1 before we embark on a month-long trek in the 29-foot Argosy.

Ok, in rough terms, like a precentage, how much of the real braking work is being done by the trailer brakes, and how much by the tow vehicle?

If my van weighs say, 4,000# and the trailer weighs 6,000# would it be reasonable to assume the 40%/60% ratio applies? Or, am I way off here?

When driving, it FEELS like the trailer is applying substantial braking, but I don't know this.
mdeneen
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Old 08-13-2004, 07:13 AM   #2
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Not a dumb question at all! After considering this for a moment, as a practical matter when your trailer is attached to the tow car, you now have a 10,000 lb vehicle that is being stopped by a total of eight brakes. When you have no trailer brakes, you're stopping the entire 10,000lb vehicle with brakes designed to stop a 4,000 lb vehicle.

Which brake set carries more load is dependant, I suppose, on the speed from which you're trying to stop, and the rate of deceleration that effectively transfers weight forward. The trailer brakes should come on slightly before the tow vehicle brakes, but I'm not sure that you can say that they carry more load during stopping. Basically, if my understanding is correct, the tow vehicle brakes stop the tow vehicle, and the trailer brakes stop the trailer, but it should all done in unison as a system.

Now, with that said, I'm certainly not a physicist and there may be folks out there who have a better understanding of the physics of stopping a trailer than I.

Roger
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Old 08-13-2004, 07:36 AM   #3
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Quote:
Originally Posted by 85MH325
....Basically, if my understanding is correct, the tow vehicle brakes stop the tow vehicle, and the trailer brakes stop the trailer, but it should all done in unison as a system.
Roger
I'm hoping that statement is true, which would imply that the ratio of trailer weight:tow vehicle weight would be the distribution of braking forces.

In practice, if that were true, your tow brakes would be under no more stress than if not towing at all. THAT sounds too good to be true, and probably isn't. OTOH, it does sound like the trailer brakes are a major, not minor part of the braking system?
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Old 08-13-2004, 08:44 AM   #4
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I believe Roger is spot-on here. Let's look at it intuitively, without any mathematics.If the brakes are not so set up, then the steering will be affected by unbalance. For example, consider when rounding a curve and a stop has to be made because of an obstruction in the highway. The brakes are applied when the vehicles are not in a straight line. If the brakes on the trailer are "slack", the trailer will attempt to push the rear of the truck to the outside of the bend. If the trailer brakes are "overtight", the rear of the truck will be drawn into the bend. Either way, steering correction will be required. Similar effects will occur if the brakes are applied when descending a steep hill with a curve. When you are on the road, you will quickly learn to adjust the brake controller by feel. If the trailer brakes are set too low, you will get that nasty push in the small of your back. If they are set too high, you will feel the trailer pulling you back. In between is the correct level, IMHO. Electric brakes are designed to operate at high temperatures, so use them a few times before making your final adjustment. If in doubt, have the trailer brakes slightly tight. Good luck! Nick.
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Old 08-13-2004, 08:54 AM   #5
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Roger and Nick are correct. The trailer should stop itself. If the tow vehicle is doing extra work, something is wrong.

The catch is the type of brake controller you are using. A Prodigy requires the tow vehicle to initiate the stop, which the Prodigy then measures and passes on to the electric trailer brakes in the form of varying voltage. This is obviously less than optimal since it requires your tow vehicle to do excess work at the outset.

Prodigy compensates for this issue with variable "boost" settings that you choose when setting up the controller. They cause the Prodigy to react more strongly when you press the brake, which is helpful when the trailer outweighs the tow vehicle (often the case).

As I understand it, the Jordan controller is superior in this regard because it measures your brake pedal effort (rather than deceleration) and hence there is no lag between pressing the brake and having the trailer brakes come on in proportion.
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Old 08-13-2004, 09:21 AM   #6
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Quote:
Originally Posted by rluhr
Roger and Nick are correct. The trailer should stop itself. If the tow vehicle is doing extra work, something is wrong.

The catch is the type of brake controller you are using. A Prodigy requires the tow vehicle to initiate the stop, which the Prodigy then measures and passes on to the electric trailer brakes in the form of varying voltage. This is obviously less than optimal since it requires your tow vehicle to do excess work at the outset.

Prodigy compensates for this issue with variable "boost" settings that you choose when setting up the controller. They cause the Prodigy to react more strongly when you press the brake, which is helpful when the trailer outweighs the tow vehicle (often the case).

As I understand it, the Jordan controller is superior in this regard because it measures your brake pedal effort (rather than deceleration) and hence there is no lag between pressing the brake and having the trailer brakes come on in proportion.
I also concur with this theory & have purchased a 'Brakesmart' controller (I think the Jordan is also an excellent unit) that uses the master cyl. pressure (indirectly through a sensor) to proportionately control the trailer brakes (by voltage/current). Our previous controller was a simple 'time-delay' ramp-up device that was fair at best & required constant adjusting.
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Old 08-13-2004, 09:22 AM   #7
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Originally Posted by rluhr
....As I understand it, the Jordan controller is superior in this regard because it measures your brake pedal effort (rather than deceleration) and hence there is no lag between pressing the brake and having the trailer brakes come on in proportion.
YIKES. This seems really important here. The controller I have is a very generic and basic thing ($69 Drawtite 'Activator') installed by the guy who welded up my hitch a couple years ago. It seems to function, but I have no idea how well, or on which principles.

So, here's another whole area I have to comprehend - controllers!
I'll study the web sites for a start - and research the threads on here.
Thanks,
mdeneen
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Old 08-13-2004, 10:05 AM   #8
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Two types of controlers.
Reactive and Proactive.
Reactive requires an enersia trigger. The basicly activate aftert the tow vehicle has made a change via and enersia sensor. The Prodogy is concidered the best of these type.

Proactive monitors actual brake input. It is done by either a control cable/device on the actual brake peddle or a hydraulic slave plumbed into the brake hydraulics. The Jordan is proably the best for modern vehicles with ABS brakes. They use a cable that activates a potentiiometer. You slam on the brakes in the truck the controler will slam on the brakes on the coach. You lightly touch the brakes the controler lightly activates. It is very liner to the what the brakes are doing on the tow rig.

Where this becomes important is you cant fool this type of controler. If you get on a slick surface the enersia controlers can be tricked with a loss of traction. This type controler is going to make the trailer do exactly the same as the tow vehicle.

You can also set it a little high if your having some issues with sway. Instead of having to reach for the controler and activate the trailer brakes you can adsust up and with a light touch on the brake peddle be able to activate the trailer brakes but not really enough to get the vehcile brakes going.

The old Kelsey Hayes controllers that date back to the 50's use to be king but they are not recomended for ABS equipped vehicles. My tow vehicle had one when I bought it and it does work quite well once adjusted. They don't have the nice diagnostics of the Jordan and they sometimes require a resistor pack to to get your rough adjustment. That ristor is located under the hood and requires getting out of the vehicle to adjust. Once dialed in its fine but it is more difficult process to make the setup for a different trailer. I pull car trailer on occasion and its a REAL hassle to adjust from empty and then adjust for loaded. Even thouhg it works great once dialed in I may switch to a Jordan just for the ease to switch set ups as well as the diagnostics feature that will let me know if it sees a brake issue on the trailer.
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Old 08-13-2004, 10:07 AM   #9
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I should point out that I'm not trying to steer you away from a Prodigy. I use it (as do many others on this board) and find it to be an excellent brake controller. Its ability to detect wiring problems *before* the brakes fail is a particular bonus.

The lag issue that I mentioned is only a theoretical concern with my combination of tow vehicle and trailer. On the other hand, my trailer is quite light (2800 lbs loaded), so "your mileage may vary."
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