Share Your Real World Tongue Weights & Trailer Weights

[Ron Gratz]

Originally Posted by A W Warn

Ron,
Would you write out the formula you used to make the calculation of the weight transferred to the TT axles, based on the dimensions you provided.
And, please elaborate on how that calculated weight might vary if the overhang was longer or shorter by just an inch or two. (I'm thinking I might drill a second hole in my hitch shank to move the ball closer to the TV, and wondering how much effect it would have)
Thanks!

Alan, if your objective is to restore a certain percentage of load to the TV's front axle, the effect of ball overhang can be determined via the following.

For:
a = TV wheelbase
b = TV ball overhang
c = distance from ball to midpoint between TT's axles
d = effective length of WD bars
TW = TT tongue weight
BARLOAD = upward force exerted on a single WD bar

Then:
load removed from front axle = TW x b / a

load restored by WDH = (2 x BARLOAD x d / c) x {(b+c) / a}

Making the load restored equal to load removed (100% FALR) gives:

BARLOAD/TW = (b / d) x {c / (b+c)} / 2 or

BARLOAD/TW = c / (2 x d) x b / (b+c)

If all parameters other than "b" remain constant, then the effect of ball overhang is given by the ratio

r = b / (b+c)

Assuming a value of 220" for "c" and 60" for the initial value of "b" gives a ratio of 0.2143.
Decreasing "b" to 59" gives a ratio of 0.2115.
For this example, a 1.7% decrease in ball overhang would result in a 1.3% decrease in required bar force.

If I didn't answer the question you were asking, let me know.

Ron

[A W Warn]

Ron,
My objective was to understand your calculation. You answered my question.
I now see that you assumed a restored front axle load using WD, and applied a ratio based on that assumption.
You also made me re-think moving my hitch forward, that most likely it would not be worth the effort. Now I need to measure my trailer and crunch the numbers to see for myself. (or, maybe I should go camping instead ;-)
Thank you!

[Al and Missy]

Weights---------------1-WD On--2- WD Off--3- TV Only
TV Front Axle-----------3260-------2940-------3480
TV Rear Axle------------3740-------4200-------2800
TT------------------------5200-------5080-----------0
TV GVW-----------------7000-------7140-------6280
GCW-------------------12200------12220-------6280

NOTES:
WD Off test and TV Only test WD bars were not included
TV GVWR 7200#
TV Max Tow 8600#
TT GVWR 6300#

Tongue--------------------720--------860-----------0
TT GWV------------------5920-------5940-----------0

Hope this formats as readable.

This is old data. I need to transfer about another 150-200# to the front to get the setup optimized. Conditions for this weigh were driver, full TV fuel, full water, empty grey and black, 45# of propane, not much else in the TT.

[2vets]

Thank you Ron! The TV ball overhang is 60 inches. However the distance between the ball and the TT axles was 180 inches not 220 inches, the reason being it is a single axle trailer and an old one at that!! How does this change my numbers....?

[Ron Gratz]

Originally Posted by 2vets

---The TV ball overhang is 60 inches. However the distance between the ball and the TT axles was 180 inches not 220 inches, the reason being it is a single axle trailer and an old one at that!! How does this change my numbers....?

The actual ball to axle distance of 180" gives an indicated TW of 666# with 166# being transferred to the TT's axle.

Ron

[Ktholin]

We are camped with a CAT scale nearby, so I have an opportunity to weigh our rig for the first time. In reviewing various posts and websites, I am a little confused. Here is what I have planned:

1. Pull fully loaded TV and Trailer on scale with steering, drive and TT axles on pads 1,2 and 3. Take weights.

2 Disconnect WD bars but leave attached to hitch (I have Equalizer system). Take second measurement.

3. Pull off scale, disconnect TT. Drive TV back on scale with WD bars attached to hitch. Measure steering and drive axles.

Is this correct and is there anything I've missed? I have seen a couple of spreadsheets for calculations. Any recommendation?

Thanks for your comments.



Sent from my iPad using Airstream Forums

[Ron Gratz]

Originally Posted by Ktholin

Is this correct and is there anything I've missed? I have seen a couple of spreadsheets for calculations. Any recommendation?

The three sets of measurements you have outlined will provide the necessary data.

For your second weighing (WD bars disconnected) the TT likely will be in a "nose down" attitude. This can cause a reduction in the measured tongue weight which will be reflected in the data.

The online spreadsheets might give an erroneous value for tongue weight because their calculations assume the tongue weight remains constant even when the TT is out of level.

If your TV has significant rear-end drop with the WD bars disconnected, the data can be adjusted to correct for the reduction in load on the ball.
If you post your data in this thread, we can help you interpret the numbers.

Ron

[Ktholin]

Thank you very much. I'll try to post the numbers tomorrow.

Keith


Sent from my iPad using Airstream Forums

[Ron Gratz]

Originally Posted by Ktholin

Thank you very much. I'll try to post the numbers tomorrow.

Keith, in addition to the axle loads, please post approximate values for:
the TV's wheelbase,
the distance from the ball to the TV's rear axle,
and the distance from the ball to the midpoint between the TT's axles.

You should ensure that the loading of the TV, including location of all occupants and cargo, is the same for all three weighings.

Ron

[Ktholin]

Thanks, Ron. I may need to get back to you with some of the measurements when we return home next Wednesday.

Keith


Sent from my iPad using Airstream Forums

[Ron Gratz]

Keith,

Tell us the year, make, model, etc for your tow vehicle and I can estimate the dimensions until you can provide the actual values.

Ron

[Ktholin]

Here are the numbers

TV + TT w/WD
Steer Axle2720
Drive Axle4840
Trailer5540
Gross 13100

TV + TT w/o WD
Steer Axle2520
Drive Axle5060
Trailer 13080

TV
Steer Axle3080
Drive Axle3340
Gross6420

I'm concerned that I don't have enough weight distribution to the steering axle. I weighed it with full propane tanks, full TV gas tank, TV loaded with 2 psgrs, generator, cooler, camping equipment. Water, grey water and black water tanks empty.

My TV is a 2007 Escalade std wheel base. I have Automatic Load Control (air shocks). How, if at all, might this affect measurements? I have an Equalizer WD system.

Thanks.




Sent from my iPad using Airstream Forums

[Ktholin]

BTW it is a 25ft flying cloud FB


Sent from my iPad using Airstream Forums

[Ron Gratz]

Keith, the numbers are self consistent -- no obvious discrepancies that I can see.

The indicated Gross Combination Weight is in the range of 13080-13100#. This should be less than the GCWR value listed in your Owners Manual.

The trailer's indicated Gross Vehicle Weight is in the range of 6660-6680#. This should be less that the trailer's GVWR printed on a sticker on the trailer.

The TV's indicated GVW, with TT attached and WD applied, is 7560#. This should be less that the TV's GVWR printed on a sticker located on the driver's door edge or pillar.

The indicated rear Gross Axle Weight, with TT attached and WD applied, is 4840. This should be less than the rear GAWR printed on the sticker.

The indicated tongue weight, with TT attached and WD not applied, is 1160#. This value is likely to be less than the actual tongue weight if the TT was in a "nose down" attitude when weighed. If your Automatic Load Control was active during this weighing, the rear-end sag might have been minimal.

The calculated tongue weight, based on assumed TV/TT dimensions and the data taken with TT attached and WD applied, was 1260# with 140# being transferred to the TT's axles via the WDH. The tongue weight should not exceed the Maximum Tongue Weight printer on the receiver's label or specified in the Owners Manual.

Your WDH should be capable of transferring a load equal to approximately 25% of the tongue weight to the TT's axles. Each additional pound of load transferred to the TT should result in an additional two pounds being transferred to the TV's front axle and an additional three pounds being removed from the TV's rear axle.

The Automatic Load Control could interfere with the adjustment of the WDH. If the ALC activates after the WDH is adjusted, any additional lifting of the rear end will cause load to be removed from the WD bars, and the load transfers to front axle and TT axles will be decreased.

Let me know if you have questions about how any of the above values were obtained.

Ron

[Ktholin]

Ron, Thanks. That is awesome! I will compare the values with my TV and TT specifications to make sure I am OK.

My ALC system was activated after the WD was set up. The TT had a nose down position, but the ALC lifted it up a couple of inches. I'm thinking I will raise the L brackets on the Equalizer hitch to transfer more load to the steering axle. That way most of the weight transfer will be done by the WD system. Does the ALC basically achieve the same result by transferring weight forward?

Thanks again,

Keith




Sent from my iPad using Airstream Forums

[Ron Gratz]

Originally Posted by Ktholin

My ALC system was activated after the WD was set up. The TT had a nose down position, but the ALC lifted it up a couple of inches. I'm thinking I will raise the L brackets on the Equalizer hitch to transfer more load to the steering axle. That way most of the weight transfer will be done by the WD system. Does the ALC basically achieve the same result by transferring weight forward?

The ALC, if it's the same as on the Suburban, uses an air compressor and air shocks to maintain the rear of the vehicle at a preset height.
If you first adjust the WDH to eliminate some or all of the front-end rise, the rear end still will remain below the preset height.
If the air leveling then is activated, the rear height will rise to the preset level.

When the height of the rear end rises, the load on the WD bars will decrease and the amount of load removed from the rear axle and transferred to the front axle and TT axles will decrease. The decreased load transfer to the front end will cause the front to rise.

The 2007 Suburban owners manual specifies:

If a weight-distributing hitch is being used, it is
recommended to allow the shocks to inflate,
thereby leveling the vehicle prior to adjusting
the hitch.

This procedure will reduce the adverse effect of using the air leveling in conjunction with the WDH.

The Owners Manuals for both the 2007 Suburban and 2007 Escalade specify the front wheel well should be at the same height before hitching and after hitching with WD applied.

Ron

[southsaglejim]

1987 excella 32 ft dry weight (no h20 in any tank was 6140 with maybe 80 lbs camp gear on board and no water in any tanks. Tongue wt 880.

Fully loaded for camping the wt was 6350. If needed I can provide more info as I have capacity specs in my manual. You should be able to email me. But if not post here.

I have also the actual weight of my F250 crew cab and the capacity specs. I towed without torsion bar hitch, but will be setting that up for balance and extra towing capacity.

[Rod Dixon]

Had my truck and trailer weights done by RVSF yesterday. I have a 2014 Flying Cloud 30' using a 2004 Chevy 2500 HD with duramax and equalizer hitch. Truck without trailer front was 1950 on driver side, passenger side front was 1975. rear on driver side was 2050 and passenger was 1800 for a total of 7775. Had Honda 3000 on driver side. Truck with trailer driver side front was 1825 and passenger side was 1825, rear driver side was 2625 and passenger side was 2325 for a total of 8600. Trailer was 1950 on front driver side and 1950 on front passenger side, rear was 1550 on driver side and 1500 on passenger side. This gave a pin wt. of 825 and a total from trailer of 7775. We had been on a three week campout.
Let me know if I need to make changes in this set up.
Rod Dixon

[southsaglejim]

What did RVSF say about your weights and setup? Should not your truck axles be a lot more equal than they are? Is your equalizer hitch adjusted correctly. I do not pretend to have answers but those would be the questions it seems to me.

[southsaglejim]

I recently went over the scales to weigh all three axles on my F250 6 liter diesel pulling the 32 ft Excella. With a weight bearing hitch setup and not an equalizer setup my front axle was 4450, rear axle was 4750 and the trailer axle was 6350 with luggage and some camp gear. My total wt of 15,550 was well under my max capacity of 21,000 and the truck axle wts were also within maximums. After that weighing I have now put on the equalizer hitch so I am interested in how the distribution might be different.