Do I need sway bars?

BigDfromTN said:

Not disputing anything you say here!!!

BUT I do know that a trailer with too little tongue weight is VERY unstable as well.  What I am unsure about is can you "Take Away" enough tongue weight with a WD hitch to cause this unstable condition? ???

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And indeed it would be unstable.  A WD hitch does not take any weight away.  It is all still there.  Some of it is merely transferred to the front axle from the rear axle of the tow vehicle.  The object is to restore the proportion of weight distribution normal for the unladen vehicle.  That is why you adjust a WD hitch by restoring the attitude of the truck to its unladen proportions. See our Library for the procedure.

Imagine the coupler ball as attached to the truck frame by a solid bar.  That bar and the frame ahead of the bar constitute a level with its fulcrum (pivot) at the rear axle.  Load tongue weight on the coupler ball and the lever pivots the front of the frame up taking load off the front axle.  A WD hitch acts on frame twisting the receiver which is welded/bolted to the frame up forcing the front down thereby restoring the proportions of weight.

Gottit?  No?  Go out to a park and tinker with the teeter-totters and you should catch on to the idea.  The board can be moved back an forth on the pivot a bit so a skinny kid can balance a big one.  Even so, the balance may not be exact so the big kid has to push up a bit to allow the little one to get back down.  That push is what the spring bars of the WD hitch provide -- more or less.

Time for a drink?  ???

Carl L said:

Trucks, and most cars, are normally are set up with an nose-heavy understeer configuration.  In  understeer, the vehicle will tend to resist a turn and try to maintain or resume a straight line course.  The vehicle is said to "plow" a turn.  This is the most controllable/stable steering configuration.

Oversteer, on the other hand, is the condition in which the vehicle tends to move easily and quickly into a turn, tending to turn tighter as it continues in the turn.  The vehicle will "dive" into a turn and evince a tendency to get "sideways" in turning.  Steering with be nervous and unstable require constant correction with the steering wheel.

Wikipedia's article on the subject:

When an understeer vehicle is taken to frictional limits where it is no longer possible to increase lateral acceleration, the vehicle will follow a path with a radius larger than intended. Although the vehicle cannot increase lateral acceleration, it is dynamically stable.

When an oversteer vehicle is taken to frictional limits, it becomes dynamically unstable with a tendency to spin out. Although the vehicle is unstable in open-loop control, a skilled driver can maintain control a little past the point of instability with counter-steering. However, at some limit in lateral acceleration, it is not physically possible for even the most skilled driver to maintain a steady state and spinout will occur.  [ http://en.wikipedia.org/wiki/Oversteer ]

Over-tightening WD spring bars will transfer an excess of trailer tongue weight forward onto the truck's front axle.  It will act to slightly stiffen the trucks steering and increase the understeer condition.  It will increase the resistance to turning.  Not all that great, but not a major concern. 

The opposite, under-tightening the bars, will shift the tongue weight back onto the rear axle and increase the oversteer tendency.  This will significantly increase the instability of the tow.  That is a really major concern.  In towing a trailer, oversteer is not our friend.  8)

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Well said and spot on sir.

Mopar1973Man said:

Reason why I asked because 99% I'm dry camping with my RV. Now I know my water tank is 50 gallons and located back by the rear bumper of the trailer. So when I left the house it was a bit squirrelly at times. Then one trip I let the bar down to the last chain link and WOW! Huge difference it drove very controlled and very solid. My Truck is already got the Camper Special suspension on it. So even without my WD bars it sits nearly level.

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50 gallon water tank back by the rear bumper!      That is the least wonderful trailer design that I have seen in recent years.  The fresh tank belongs ahead of the trailer axle where it can contribute positively to balance.

Carl L said:

50 gallon water tank back by the rear bumper!      That is the least wonderful trailer design that I have seen in recent years.  The fresh tank belongs ahead of the trailer axle where it can contribute positively to balance.

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I dont recall the gallons but my Fresh water tank is in the same position.  Grey tank is above rear axle and Black tank just behind it.

I can see the need to possibly adjust the links based on the tank being full or empty.

Yea... 50 gallons at the trailer rear bumper. Exactly like Carl L  :

But it's odd if I set the WD bar up the same way the dealer set it up it feels squirrelly or get sway easy. But now let up 1 link (last link) in the WD bars the rear axle springs of the truck squat slightly and the truck feels much more stable. Why? I'm not sure. (Puzzled Smiley here)

Mopar1973Man said:

Yea... 50 gallons at the trailer rear bumper. Exactly like Carl L  :

But it's odd if I set the WD bar up the same way the dealer set it up it feels squirrelly or get sway easy. But now let up 1 link (last link) in the WD bars the rear axle springs of the truck squat slightly and the truck feels much more stable. Why? I'm not sure. (Puzzled Smiley here)

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Because you are putting some weight back on the tongue would be my guess.  ????
Weight that was removed by the extra weight at the rear of the trailer which uses the axles as a fulcrum (described earlier by other poster).  Thats my un educated guess!!!

BigD is right on the money.  50 gals of water is 400+ lbs and its well behind the axle (fulcrum). That lifts at least that much weight off the tongue (actually quite a bit more), so you need much less weight compensation from the spring bars.

Thank guys (BigD and Gary)!!!  8)

Gary RVer Emeritus said:

Sway is also affected by trailer balance. The MORE weight there is on the tongue, the LESS sway. A tongue weight under 10% will start swaying at the slightest provocation, whereas 12%-15% probably won't sway except in extreme conditions.

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Hi Gary, I am also a newbie shopping for the correct Rv for my ability to tow. I was reading through this thread & had a question about your comment.

Does "hitch weight" = " weight on the tongue"?

Is it better to choose an RV with a higher hitch weight as opposed to a lower one?

Can the sway control be added later? Or do you have to buy a whole new set up?

Does "hitch weight" = " weight on the tongue"? Basically, yes. It is the weight the trailer puts on the TV hitch

Is it better to choose an RV with a higher hitch weight as opposed to a lower one? Not your choice for the most part. It starts will the design of the trailer which should be designed to have 10% on the hitch.

"Bumper pull" (Travel)  Trailers are designed to put 10% of their total weight onto the hitch. How you place additional load in the trailer will affect this number. Most recommend you shoot for 10-12%. A fifth wheel trailer is designed to put a minimum of 20% of its total weight on the truck, (often called "pin weight"). Again, loading can affect this and the recommendation is usually 20-25%

Can the sway control be added later? Or do you have to buy a whole new set up? It can usually be added later, but it is usually recommended here to start out using a hitch that includes both weight distribution and sway control.

Frizlefrak said:

ROFL....that describes it perfectly.  Only had it happen once when I was young and didn't know any better.  Nothing gets your attention like a swaying trailer.

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I experienced this when I was 16 towing an 18' trailer with a 1970 Monte Carlo down a long, downhill grade out of the mountains in Arizona while on vacation with my folks.  I hadn't been driving that long, maybe 6 months, and my dad trusted me behind the wheel.  It was 2 lanes wide coming down and I was probably running 70 mph when it started.  I was using the better part of both lanes to get it straightened out.  We were all lucky that there was nobody beside us when it happened. 

So if I''m looking at a trailer to buy & it's UVW is 4450 & has a hitch weight of 390 I should probably not buy it?

Yes, you need Sway Control (Bars). 

Gary RVer Emeritus said:

Trailers don't come with anti-sway bars or devices - the previous owner must have been thinking of something else.

A WD hitch with anti-sway control built in (integrated) is highly recommended, for both safety and convenience. I like the Equal-i-zer, Reese Dual Cam, Hensley Arrow or Pro-pride brands. The last two are ultra-expensive but set the gold standard for hitches. The first do do a fine job, though, and should be plenty adequate for your trailer.

BTW, those bars on the hitch are not "sway bars" - they are the weight equalizing mechanism. The anti-sway function is either intergrated in the hitch head or accomplished with an add-on friction pad device that you manually adjust.

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What are your thoughts about the Blue Ox system?  http://www.blueox.com/trailertowing/swaypro/

This is what we have. We love it.
https://www.etrailer.com/Weight-Distribution/Reese/RP66151.html

Gary RVer Emeritus said:

BigD is right on the money.  50 gals of water is 400+ lbs and its well behind the axle (fulcrum). That lifts at least that much weight off the tongue (actually quite a bit more), so you need much less weight compensation from the spring bars.

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I actually had a guy who was trying to sell me a camper without including the weight distribution hitch, tell me that since the kitchen was in the back of the camper I didn't need them. He didn't have a good answer when I asked him why he had them in the first place then.....and no, I didn't buy that one 

in answer to the OP, yes you will find yourself wishing you had sway control at some point if you don't use it. The white knuckle freak show mentioned above is a very accurate description the first time a truck or bus or strong cross wind hits you