OK, Question about Brakes/Breakaway Switch

[Tim5055]

I thought I had a clear understanding of this and on my web-page I make the following statement:

The theory is that should your pop up disconnect from the tow vehicle, the trailer will fall back from the tow vehicle.  If the chains are the correct length and are crossed in an "X", the chains will cradle the front of the A frame.  Now, if you measured the break away switch cable correctly, it will have been shorter than the chains and will have activated the brakes as the trailer fell back  With the brakes fully activated, the trailer should track fairly straight and allow you to pull to the side of the road.  Should it happen, you will probably need a new set of tires, as locking the brakes at full speed is not great for the tires, put you should still have a pop up.  Oh, you will probably need new undies too

Today I received the following e-mail:

Your breakaway stuff is dead wrong. A breakaway switch is for when the trailer and tow vehicle are completely separated.
The breakaway cable is longer than your chains. If you're dragging the trailer by your safety chains you should still have electrical connection intact and so you're still able to work the trailer brakes (and brake lights too) from the tow
vehicle's brake controller. So you breakaway cable is longer than your electrical cable which is longer than your safety chains. That's how it works. You're giving people really dangerous advice!

Now, all the research I have done indicates the breakaway switch should be shorter thant he chains in order to apply the brakes before the trailer becomes totally detached.  The argument I have read is that the brakes should apply for for a couple of reasons:

• You may not notice the disconnect if the brakes didn't apply
• There is a greater chance of the chains failing with the trailer whipping around behind you.  Having the brakes applied will cause the trailer to track straight behind you.
• What good does the brakes being applied do in a total disconnect.  With no connection to the tow vehicle the trailer will become an unguided missile anyway.

I'm always willing to learn.  Any thoughts?

[tlhdoc]

I am with the break away cable should be longer than the safety chain group.

I can't believe you wouldn't notice the trailer was off the ball.  I don't think it would tow very straight if it is being towed by just the chains.  You can still apply the brakes manually because the plug is still in and you will not lock up the wheels.  I agree that there is a greater chance of the chains falling if the trailer is whipping around, but if you apply the brakes manually the trailer should not be whipping around.  With a total disconnect applying the brakes may prevent the trailer from hitting other vehicles of even your own vehicle when you stop because you lost your trailer, and may prevent the trailer from being totaled.

[Gone-Camping]

I'm afraid I have to agree with the disenter on this. Every trailer I've had, including those with Surge Brakes, the break-away cable has always been nearly twice as long as the chains. And he's right about another point, if you're still dragging by the chains, then the electrical hook-up should still be intact.

I'll add one more "observation" though it may or may not be supported by fact. Seems to me that once those trailer brakes lock-up, there is going to be loss of control on the trailer, such as a skidding car has no control.

[Tim5055]

OK,  I can go either way on this but am looking for a technical resource.  I have read the DOT guidelines, manufacturer web sites and everything else I could find.

It is sad to say, there is very little written on the subject. But the few I have found that give few details other than "The theory is that if your coupler becomes separated from the tow ball the plunger of the breakaway switch will come out thereby completing the electrical circuit, allowing the battery to provide power to the electric brakes and bringing your trailer to a stop." http://www.trailercanada.com/trailertips.htm

The only details I have found were on this page:

"The rip cord should be long enough not to snag on hitch parts when turning, but short enough to pop out of the break-away switch before the loose trailer can pull the safety chains taught."
http://www.whmentors.org/saf/trailer.html


Now, neither of these sites is what I would call authoritative, for that matter neither is my site :rolleyes:

I am always willing to learn and wonder if there is something out there.

[Used 2B PopUPTimes]

I found this on http://www.classicmfg.com/manual2.htm#2.2.1.5
 

Connect the pull-pin cable to the tow vehicle so that the pull-pin will be pulled out before all of the slack in the safety chains is taken up (see Breakaway Brake System figure). Do not connect the pull-pin cable to a safety chain or to the hitch ball or hitch ball assembly. This would keep the breakaway brake system from operating when it is needed.


Tim's right

[aw738]

I don't know what kind of chain is on your PU but the chains that came on mine are not very strong looking chains. If the brakes engage before the slack is taken up in the chain it is going to put a heavy shock load on the chain and the attachment points on the PU or TV.  A broken chain or anchor point is as bad as none at all. If the chains catch the tounge as designed without appling the brakes fully you could still get off to the side of the road but if the brakes are applied it would be hard to move the PU. Taking into acount if it didn't break something and disconnect fully.

[topcat7736]

The chains are crossed to "catch" the coupler if the two vehicles become disconnected. The breakaway switch cable must pull away before the slack in the chains is reached. This will cause the trailers brakes to be applied, before the coupler is "caught", and the trailer will in turn begin slowing the towing vehicle. With the chains pulled to full length, the two vehicles can be safely driven to the side of the road without the tongue being dragged on the ground. Dot publication HS-802586 covers the connections and an excerpt can be found here:
DOT HS-802586
Also:
Installation of brake buddy breakaway system

I would imagine that the breakaway cables are shipped in longer lengths because there is no set length between the towing vehicles and the trailers. The cable would be trimmed or shortened at the time of installation.

Darn, I hate it when Tim's right!  

[Tim5055]

Darn, I hate it when Tim's right!  

 :confused:



Thanks for the support Al


If anyone else knows of sites with information, please let me know.

Thanks

[tlhdoc]

Tim that wasn't nice setting us up like that.  I should have know Natasha would have the proper information on her web site. :p

[Tim5055]

Tim that wasn't nice setting us up like that.  I should have know Natasha would have the proper information on her web site. :p

I swear, no set up.  This was the way our dealer taught us, but you know the quality of information you get from dealers sometimes :eek:

I jsut want to make sure I'm giving out good information.

[AustinBoston]

This is an issue where I have (at one time or another) strongly held both sides.  I have had long (theoretical) discussions about the merits of one or the other, but never seen documentation one way or another.  But there are some basic facts:

Rules about breakaway brakes (whether federal or state) are not designed with the preservation of either the trailer or the tow vehicle in mind.  They are designed with the protection of other road users in mind.

If the trailer separates completely (loss of chains), the breakaway brakes are the only thing that will keep it from travelling a long ways in it's current direction.

A disconnect (with chains intact) is a relatively violent event at highway speeds and is likely to result in the trailer tongue repeatedly making significant contact with the back of the tow vehicle.

A skidding trailer will not track straight and can jacknife or roll.

It seems to me that all of the pro/con arguments boil down to weighing the last two.  They work like this:

A) If the breakaway brakes are not applied until loss of chains, you will have a trailer that is surging, rebounding, and banging into the tow vehicle.  The tongue will not gently or quietly follow the tow vehicle, and that electrical connection you are relying on to activate the trailer brakes may be ripped out inside the first two seconds.  With all that motion, including forward/backward, up/down, and side/side, there is a significant risk of loosing the chains as well as the electrical connection, and then you have a loose trailer on the road.

B) If the breakaway brakes are applied while the trailer is still connected, there is a risk that the breakaway activation itself could cause the chains to fail, especially if there is more than an inch or two of slack left in the chains. (Who measures that to the inch?)  Even if the chains don't fail, unless your brakes are too small for the trailer, the breakaway brakes will lock the trailer wheels.  Locked wheels have no directional control, and so the trailer now will not reliably track the tow vehicle.  It can easily end up far to the side of the tow vehicle, and in that position has a high possibility of rolling.

Which is correct?  I believe both of these arguments are correct.  If the breakaway brakes apply with the chains still connected, very bad things can happen.  If they don't apply unless the chains fail, very bad things can happen.

Choose your poison.

Austin

[mike4947]

SInce I've BEEN posioned twice over the years I pick having the breakaway activated after the coupler leaves the ball and before the trailer breaks free of the chains.

If you have proper length chains crossed to catch the tongue of the trailer, the trailer brakes keep the chains tight and tracking behind the TV.
 
The force the trailer exerts on the chains is minimal. Your talking about inches and a second so there's very little change in velocity on the trailer in that short space of time. The trailer ain't going to go from 60 to zero in the length of time and length of chain.
 
In both the breakaways the worst damage was one small dent in a rear bumper and both times the trailer was brought to a safe stop, rehooked up and we continued.
 
Problem isn't the breakaway, the problem is the ignorance of the tow vehicle operator.
At one Roundup in Ohio several hundred trailer towing setups were checked.
Know how many of them passed with flying colors?        4
Mine wasn't one of them, but within an hour it passed and I hate to image what either of the breakaways would have been if we hadn't learned that day what it took to get a correct setup .
IMHO 99 out of every 100 towing setups could be improved/made safer.
There are to many people towing fat, dumb and happy.

[moderator1]

Weaaaaa

[4Galvs]

Any idea how a breakaway cable is supposed to be set up for surge brakes?  Our 12FSO has a breakway cable mounted to the brake master cylinder.  I hook the opposite end (S-hook) behind the clip around the draw bar pin.  If memory serves, the cable is a bit longer than the chains.

[mike4947]

Any idea how a breakaway cable is supposed to be set up for surge brakes? Our 12FSO has a breakway cable mounted to the brake master cylinder. I hook the opposite end (S-hook) behind the clip around the draw bar pin. If memory serves, the cable is a bit longer than the chains.

The chains and cables are IMHO never the correct lengths. That was the most common problem we saw at that clinic in Ohio.
 
What we were taught was the chains should be of a length that allows for turning (up to and including an angle that the TV contacts the trailer), be attached to the trailer one on each side of the tongue and crossed and attached at two different points on the opposite side of the coupler on the TV, to form a "bucket" to catch the trailer tongue before it contacts the pavement in the result of a disconnect. Their connection to the trailer should be permanent and the non permanent connection to the TV should be with closable ring type connectors not open S hooks.
For those of you with electric brakes a breakaway cable on a surge brake equiped trailer is designed  not to "break" but to actually pull on the master cylinder.
The breakaway (I happen to have a Rockwood with surge brakes at that rally, so I can give you the exact advice I got) cable for surge brakes works by pulling on the lever mounted on the master cylinder activating the brakes. The cable should be connected on the TV at a point at or near the centerline of the TV/trailer and feed over/under the ball/coupler connection with as little slack as need to allow for turns. That way in a disconnect the cable will start pulling as soon as the coupler leaves the ball and activate the brakes starting before the chains get tight.
 
I've found that with any of our towed RV's with brakes it takes about 2-3 hours of measuring and fitting to get the setup right and in 20 years I've seen a really correct towing setup from a dealer only once or twice, and again JMHO they were mostly luck.