Towing experience with Santa Fe (07-12)? - Page 2 - Fiberglass RV

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Old 05-11-2015, 08:12 AM   #15
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Name: JD
Trailer: Scamp
Posts: 765
The weight distribution hitch shifts weight to the front of the TV by adding stiffness across the hitch. It also add weight to the tires of the trailer as well. The proportion is roughly equal to the distance from hitch to the front and the hitch to the trailer axle. The research indicated that the majority of the stabilization is due to the shift of the weight to the trailer axle. (see sited information above).
The shift of weight to the front of the TV will tend to make the car understeer more which is a good thing towing.
Adding the air bags will stiffen the rear end which will raise the resonant frequency of the back of the TV and should be accompanied by stiffer shock absorbers which will also dampen the oscillations at the rear.
If the resonant frequency of the trailer coincides with the resonant frequency of the TV the result is the undulating ride experienced.
The fix is to shift the ride characteristics of the tow vehicle out of this range with the airbags. Their effect can be removed by deflating to 5 psi when not towing.
These will also level the rig and again research has shown that a large part of the loss of stability is the lowered roll center of the combination and the unfavorable roll couple when the rear end sags.
The easiest fix would be to add air shocks if available for the Santa Fe or air bags if not.
Of course a WDH could be added, but it seems overkill on a Trillium 1300 at 1500 lbs and (I assume 13').
Here is a post on air bags from another forum:
Air Shocks - Hyundai Forums : Hyundai Forum
Here is what I found on an adjustable shock absorber, but according to the description modifications may have to be made for it to fit:
Rancho R38RS999292 Shock Absorber and Strut Assembly | Auto Parts Warehouse
Here is a link to Monroe:
There are few choices for the Santa Fe available.
The handling is one of the reasons I went that another VW Sportwagon to tow my 16" Scamp. The car is well damped with and without the trailer.
By the way most of the old dat form the studies on the interaction between trailers and cars is still valid and if it is actually read may add some understanding the the dynamics involved.
You cannot digest the data and tests in less than 22 minutes.
The dynamics of the trailer has not changed at all in the last 35 years and without a doubt the cars have improved quite a bit so the handling should be better. The interactions are very much the same when adding the trailer to a better handling car.
My experience with the VW has proven this to be the case. A poorly suspended TV is will not get better with a trailer attached.
Your experience may differ.

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Old 05-11-2015, 08:35 AM   #16
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Name: Bob
Trailer: 1973 Hunter Compact II
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Nope, one can't "digest" the information in 22 minutes, but they can read the 4 summaries and keyword search the documents in that period of time, and there is nothing to indicate that Air springs were 50% as effective as a WDH. Can you point to where that is supported?

BTW: I doubt if 5% of the readers have a grasp on what "Resonant Frequency" between TV and trailer even means. It's usually better to write to the level of the audience, not to mention inserting <cr>'s between paragraphs to improve readability.

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Old 05-11-2015, 11:17 AM   #17
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Name: JD
Trailer: Scamp
Posts: 765
Page 112 of ECD 1082 Graph show the 50% with air lift alone.
In all cases where the WDH was used the setup was level the vehicle to the max with Gabriel HiJacker shocks and then adjust the load leveling hitch to level.

Since this won't be settled they I suggest everyone get a load leveler for their 1500 lb trailer to pull with a 5000 lb vehicle.
Probably best is a 3/4 1 ton truck with WDH and just set the trailer in the back.

Of course most of us have the small fiberglass trailer so that we can tow them with a smaller vehicle so it might help to investigate what works best with that setup.
Again if you actually look at the data and graphs you will see the minimum WDH shown which is air levelers alone and no torque on the hitch!

This is about 50% of the improvement with the hitch adjusted to the max settings.
Plus this sets the TV to the correct ride height for headlights and suspension setup.
The rest of the combination is to increase the air pressure in the TV rear tires (suggested in tire manufacturers max cold) to stiffen the sidewalls and the same with the trailer. This is to increase the damping and limit the swing.

Many of the new unibody cars do not allow for weight distributing hitches (probably due to body construction of sheet metal) and for sure VW does not. They do state that additional heavy duty springs (or air shocks) may be necessary)

I don't know about Hyundai and WDH addition. There are limited choices for adding stiffer shocks as well, but the air pressures could and should be increased.

I am surprised that the trillium 1300 causes problems with a max gross weight of 5512 lbs and a max towing capacity of 5000 lbs. ( for the 2015 GLS V6). At 4000 lbs empty and the weight of the trillium at 1800 lbs the ratio is .45 and should not be a problem.

I am not trying to start an argument, but rather suggest something that will help the OP. The data is the data.

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