Load sensing suspension and Equalizing hitch.

[59toaster]

I responded to a post and after finding out their TV had load sensing suspension it got me thinking........I know I'm dangerous at this point. With more and more vehicles having load sensing suspension I realized a lot of people might be getting unknowingly into a "over-hitched" condition that we have often spoke of.

So I thought I would throw this out here and see what others think and if they agree with my thoughts on this.

Here is what I posted to this person when the queried about the Equalizer hitch to help with sway:




The way a LOT of these type of sway control work is this:

The Trunnion where the equalizer bars go in is set at an angle. If you drew a line through the pivot axis you would want that axis leaning back toward the trailer. What will happen is when you tension the bars they will want to seek less tension and will want to swing out away from the A-Frame. With one on either side of the A-frame they will counter balance each other and try to center the trailer to the tow vehicle.

So understanding that you will see that when sway begins and try to pivot side to side at the ball that one equalizer bar will loose tension and the opposite will gain tension. They will want to "equalize" that tension and to do so the trailer needs to center on the the tow vehicle.

Now here is where people get in trouble.

A hitch set up that would work perfect for a Cadillac would not work correctly for a 3/4 ton truck. The equalizer bars rating is critical. A caddie with soft suspension would need a higher rated bar. The load and subsequent deflection of the bar is VERY important.

On the caddie with soft suspension and a tongue weight of 750lb and bars rated 750lb. Without those bars hooked up the back bumper of the car would practically be on the ground and drop about 6 inches. Once you pull the bars up you level out the tow vehicle and those bars have about 2 inches of deflection. If you slam on the brakes and the nose of the car dives you still have plenty of tension on the bars to get that equalizing effect.

Now you take that same set up and put that on the back of a 3/4 ton truck here is what happens:

The truck has enough suspension that even with that amount of tongue weight the rear of the truck only goes down about 3/4 of an inch. So you need much LESS tension on the equalizer bars to get the 3/4 ton truck back to level. The bars only deflect .5 inches. In the same situation of slamming on the brakes and getting nose dive the bars will loose ALL tension and if that happens you will also loose your sway control at the most critical time you need it. The trailer can then push the the tow vehicle sideways because the loss of sway control that would normally fight to prevent that.

So the lesson is: The more stout the suspension on the tow vehicle you need to go to softer on the Equalizer bars to get the defection in the bar to make the sway control tendency effective.


In your case I did a little snooping and found you plan to tow with a car that has load leveling suspension. That throws a new variable in. Your vehicle has to capability of increasing its spring rate and it makes choosing bars AND your hook up procedure much more complicated. You vehicle can become a 3/4 ton truck without you realizing it.

I would be REAL cautious about how you hook up the first couple times. Ideally you want to transfer weight from the ball to the front suspension of the TV and the trailer suspension. I would do some investigation of how that load leveling suspension works and I would strongly consider crippling it till you get the coach hooked up and level the first time. With that load sensing feature once you drop the load on the ball the car is going to try to level and to do so it just stiffened up the rear suspension and your 750lb bars are now incorrect.

If you can shut off that feature then level the TV with the equalizer bars then reactivate the suspension you would get the desired weight transfer and deflection on the bars for your sway control. You may only need to do this the very first time. Once you know what link to put the bars on then the car will settle back to the intension position and soften the rear suspension and all will be well.

[bryanl]

If you are adjusting a load leveling system for a tow vehicle with adaptive suspension, you need to read and follow the owner's manual very carefully. You might find that a load leveling trailer hitch is not recommended. Other times, it can be deactivated to set the hitch adjustments than reactivated when hitched up.

Sway is an entirely different matter than load leveling. The spring bars have very little to do with sway because that is a horizontal problem and load leveling is vertical. The major factors involved in sway are load positioning, the ratios between axles and the hitch point, factors that resist or control horizontal movement in the tow vehicle and trailer, and control over the pivoting at the hitch point.

And, I think, it is easy to confuse Equal-i-zer brand hitches that have an integral sway control as described with generic equalizer hitches such as EAZ Lift that are load leveling only.

[59toaster]

Originally Posted by Leipper

If you are adjusting a load leveling system for a tow vehicle with adaptive suspension, you need to read and follow the owner's manual very carefully. You might find that a load leveling trailer hitch is not recommended. Other times, it can be deactivated to set the hitch adjustments than reactivated when hitched up.

Sway is an entirely different matter than load leveling. The spring bars have very little to do with sway because that is a horizontal problem and load leveling is vertical. The major factors involved in sway are load positioning, the ratios between axles and the hitch point, factors that resist or control horizontal movement in the tow vehicle and trailer, and control over the pivoting at the hitch point.

And, I think, it is easy to confuse Equal-i-zer brand hitches that have an integral sway control as described with generic equalizer hitches such as EAZ Lift that are load leveling only.

If you have a tilted trunnion it will help with sway even if its chains at the end. Take a look at the most popular sway control designs that do not use a friction device.

The only time the bars do not play into sway control is if there is no angle on the trunnion.

In the Case of a DC Reese the tension is VERY important. All the sway control is in the the leveling bar attachment.

Even the Hensley Arrow uses its bars as the connection to aid in sway but uses a cam at the hits where the load bars are seated.

This is the system I was referring to and it is a sway control system that is dependent on tension and trunnion angle to function.

http://www.hitchsource.com/product_i...ducts_id=27359

[Inland RV Center, In]

Generally speaking, an automatic leveling system for a tow vehcile, should be disabled when your going to tow a trailer using a load equalizing hitch.

The automatic part of that system "WILL" defeat the effectiveness of the load equalizing hitch, and cause considerable instability.

Caravanner Insurance proved beyond any doubt back in 1970, that an "automatic" leveling system, must be defeated, and the air shock pressure be reduced to keep the tow vehicle level, with "NOTHING" in the trunk of a car, as well as nothing in the bed of a pickup.

Then, when the trailer is attached to the tow vehicle using a load equalizing hitch, the proper amount of load shifting will take place, That will provide a stable rig.

The automatic system continuously fights with a load eqaulizing hitch.

Andy

[wkerfoot]

Originally Posted by Inland RV Center, In

Generally speaking, an automatic leveling system for a tow vehcile, should be disabled when your going to tow a trailer using a load equalizing hitch.

The automatic part of that system "WILL" defeat the effectiveness of the load equalizing hitch, and cause considerable instability.

Caravanner Insurance proved beyond any doubt back in 1970, that an "automatic" leveling system, must be defeated, and the air shock pressure be reduced to keep the tow vehicle level, with "NOTHING" in the trunk of a car, as well as nothing in the bed of a pickup.

Then, when the trailer is attached to the tow vehicle using a load equalizing hitch, the proper amount of load shifting will take place, That will provide a stable rig.

The automatic system continuously fights with a load eqaulizing hitch.

Andy

Andy,

After you have leveled up the tow vehicle with the hitch, can you then put items in the trunk and truck bed or do you have to travel empty? If so, won't you be tail down then?

Bill

[Inland RV Center, In]

Bill.

Sorry, I left that good part out.

After defeating the automatic system, and leveling your tow vehicle with the air pressure, you can now add whatever weight you need to carry, in the trunk or bed of the truck.

The rear end may sag. That's great if it does.

Hook your trailer up, and adjust the load equalizing hitch as necessary. You may have to shorten the chain by a link or two.

That will result in the proper distribution of the "tongue weight" and very importantly, the "trunk or bed weight as well".

You will now have a very stable towing rig.

Andy