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Old 02-24-2013, 12:55 PM   #1
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Weight Distribution & WD Hitches In General

There has been a lot of consideration to WD in JOF lately. This post is intended to be helpful by providing what I hope is useful information.

With the help of JOF I’m starting to understand the obvious elements of weight distribution (and working on the not so obvious). Rustic Eagle’s comments that make sense of the numbers have been a huge help. The information available from WDH manufacturers is now easier to read and comprehend.

I had all the misconceptions about WD and hitches that the manufacturers seem to deal with on a regular basis. Here are some “snips” from information I received from the manufacturer of my WDH. (They don’t have their name on it, so I didn’t include it. It’s a name you would recognize.) I added the Bolding in the quoted material:

“By attaching a trailer to the back of a vehicle (behind the rear axle) it creates a teeter-totter effect with the rear axle acting as a fulcrum. The weight on the front axle is reduced and the rear axle weight is increased by an amount equal to the trailer tongue weight plus the amount taken from the front axle.”

“Weight distribution will help reduce the teeter-totter effects. A weight distribution hitch creates a stiff joint between the tow vehicle and trailer that prevents the connection point from sagging. This transfers back the original weight taken from the front axle of the tow vehicle. Also, the tongue weight is split between the rear axle of the tow vehicle and the trailer axle(s). When done properly, weight distribution restores the "grip" of the front steering tires, relieves the load on the rear axle, and increases the stiffness of the connection point and the overall stability of the combination.”


“Misconception
For many people, proper weight distribution is misunderstood. The levelness of the truck and trailer do not indicate proper weight distribution. Weight distribution and the levelness of the trailer are two separate issues. They do influence each other, but are not directly related. The hitch ball height needs to be adjusted in conjunction with the weight distribution settings to achieve both proper weight distribution and a level trailer.”

“Insufficient weight distribution is obviously undesirable. Too much weight distribution is also detrimental. With too much weight distribution the rear tires of the tow vehicle can lose traction allowing the trailer to push or pull the back of the tow vehicle around creating a possible "jack knife" scenario. Too much weight distribution can also overload the hitch, receiver, or trailer frame/coupler.”


... at this point the author referenced a FALR number. If you want to take a technical adventure, that would be a good one. Considering FALR, if you can’t hit the exact amount of weight to transfer back to the front axle, it’s better to transfer less. Or, if your using wheel-well measurements, the front readings would be slightly higher.


“Tongue Weight Rating
The weight distribution hitch has to carry the tongue weight and be able to handle the weight distribution forces. The tongue weight rating on a weight distribution hitch takes into account the tongue weight of the trailer and the forces required to obtain proper weight distribution.”

“Hitch Overload
It is common for a hitch to be loaded over its tongue weight rating. Either the actual tongue weight of the trailer is too high or the weight distribution is set too high.”

“A specific case of overloading the hitch would be trying to raise up or distribute the weight of a tow vehicle that is very loaded and riding low. To distribute the cargo weight of a tow vehicle when the trailer tongue weight is already close to the hitch tongue weight rating could cause the hitch to be overloaded. (Also, it is possible to exceed the tow vehicle's rear axle rating when hauling lots of cargo in the tow vehicle and a trailer with a high tongue weight.) For example, a pickup truck with an ATV in the back would be a likely candidate for this scenario.”
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Old 02-24-2013, 06:06 PM   #2
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OnTheGo,

I agree, there is a lot going on with a WDH and proper adjustment is critical....., informative and interesting post,

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Originally Posted by OnTheGo View Post
snip...... Also, the tongue weight is split between the rear axle of the tow vehicle and the trailer axle(s)..... snip
For clarification: Actually the tongue weight remains a constant on the TV's hitch ball (not necessarily split), the weight added to the TV's rear axle (and weight removed from the TV's steering axle) represents the "effect" of the tongue weight on the hitch ball. In most cases at the end of the day the weights being distributed are notably less than the actual tongue weight value.... different suspensions, different results.

Bob
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Old 02-24-2013, 06:30 PM   #3
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Thanks on the go. I have spent a lot of time on this for the past few weeks, it has been quite the learning experience. Help from numerous members has been invaluable.

As soon as all the snow melts it is going to the CAT scale.
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Old 02-24-2013, 06:42 PM   #4
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Good post. I am again, a little confused about something, when you say the tongue weight "remains the same" after the WDH bars are engaged, what is the impact on the payload of the TV? Does the weight transferred back to the TT axle still have to be taken away from the GVWR?

In my case, the CAT scale showed ~400lbs added to the TV with the bars engaged, 620 when they were not. Would I have to subtract the additional 220lbs from the payload even though it's no longer on the rear axle of the TV?

I hope that question makes sense, I really want to get a good grasp on how this all works.
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Old 02-24-2013, 07:51 PM   #5
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Quote:
Originally Posted by amabee View Post
snip..... when you say the tongue weight "remains the same" after the WDH bars are engaged, what is the impact on the payload of the TV? .... snip
The weight that is reduced was taken from the weight load over the TV's rear axle.

Your CAT scaled 620lb loaded TT tongue weight (on hitch ball) resulted in an added 400lbs to the TV's GVW (CAT 2nd weigh, WDH engaged). To determine the impact against the TV's payload you must compare this particular TV GVW to your TV's specified GVWR.

Quote:
Originally Posted by amabee View Post
snip..... Does the weight transferred back to the TT axle still have to be taken away from the GVWR? .... snip..... Would I have to subtract the additional 220lbs from the payload even though it's no longer on the rear axle of the TV?.... snip
The simple answer is no to both questions, all weights are accounted for (distributed) and reflected during your CAT scale weigh-in process.

If my memory serves me correctly your CAT scale results reflected that you still needed to adjust your WDH to remove about 100lbs from your TV's steering axle (WDH distribution overload). Until you make this adjustment IMO your CAT scale data is a little shy of being accurate.

Reference CAT scale data: https://www.jaycoowners.com/showthrea...-weights/page2

Hope this helps.

Bob
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Old 02-25-2013, 03:56 AM   #6
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Bob, Thanks for the clarification. I wrestled with that statement before posting, and wasn't confident to change or remove it. I think they mean the trailer (not tongue) weight is resting on the the rear axle of the tow vehicle and the trailer axle(s). They could have expressed that better, or left it out.

Quote:
snip...... Also, the tongue weight is split between the rear axle of the tow vehicle and the trailer axle(s)..... snip
For clarification: Actually the tongue weight remains a constant on the TV's hitch ball (not necessarily split),
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Old 02-25-2013, 06:36 AM   #7
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...using amabeeís CAT Scale weights step-by-step to explain distributed weight.

...using amabee’s CAT Scale weights step-by-step to explain distributed weight.

1st weigh:
Steer axle 3500
Drive Axle 2640
GW 6140

2nd weigh:
(spring bars engaged)
Steer axle 3600
Drive axle 2940
Trailer axle 3140
GW 9680

3rd weigh:
Steer axle 3280
Drive Axle 3480
Trailer axle 2940
GW 9700

Rustic Eagle, once again, your comments are solicited and appreciated.

At the CAT Scale, amabee’s TV by itself (1st weigh) weighed 3500 + 2640 = 6140.

After coupling the trailer, and not applying WD (3rd weigh), his TV weight became 3280 + 3480 = 6760

6760 – 6140 = 620 That means the tongue weight of the TT is 620, and that is not going to change. (At least during this weigh.) So, 620 pounds was added to the TV as hitch weight. Also, notice the steering axle decreased by 3500 - 3280 = 220 pounds.


Go back to the 1st weigh: The TV’s rear axle was 2640. After the 3rd weigh, with the TV coupled (no WD), the rear axle weight is 3480. 3480 – 2640 = 840. Using the figures, we know the weight on the rear axle increased 840 pounds after coupling the TT. We also know the tongue weight added 620 pounds to the rear axle as hitch weight. The difference, 840 – 620 = 220 pounds.

That 220 pounds was weight that shifted from the TV’s front axle back to the rear axle of the TV, caused by adding hitch (the TT’s tongue) weight. At this point you need to shift that 220 pounds back to the front axle to recover the TV’s handling characteristics – and that is the job of a weight distributing hitch.

When you apply the bars of the weight distributing system to your hitch and TT, they are relaxed. As you apply weight to them they use properties that were engineered into them to flex. (I don’t know if the term is spring, torque, torsion, or something else. Since were calling them spring bars, “spring” will work.) The spring action of the bars creates a force that raises the hitch end of the TV, and tongue end of the TT.

You want the bars to flex to the extent they create enough force to RAISE (not change) the hitch weight. In this case, if that RAISE causes a 220 pound transfer back to the front axle, the WDH has done it’s job. Don’t forget you have adjustments that can be made to affect tension. My WDH instructions recommend hitch head “tilt” adjustments first, and then bar height adjustments.

Looking back over this whole process, you didn’t change the weight of your TV or TT. You ended up with certain axle weights, and you distributed some of the weight back to the steering axle. Ideally, the same weight that you started with.

At the start of the weighing process, the rear of your TV probably “squatted” some from the additional weight. So, what did change was the height of the hitch (... easier for me to visualize the ball). That said: If you weighed yourself on a bathroom scale, and then put the scale at a different height, you still weigh the same.

I don’t have any experience with lift kits, but I think that’s how they would apply – by changing the height of the weight, but not the weight itself.
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Old 02-25-2013, 07:40 AM   #8
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OnTheGo,

Nice detailed walk-thru using member "amabee's" CAT scale information (thank you "amabee") as an example on what information the CAT scale provides and the function of the WDH in conjunction with the CAT scale data.

Quote:
Originally Posted by OnTheGo View Post
snip.... Looking back over this whole process, you didn’t change the weight of your TV or TT. You ended up with certain axle weights, and you distributed some of the weight back to the steering axle. Ideally, the same weight that you started with. ..... snip
I may be mis-interpreting your statement, please correct me if I'm wrong ...; For clarification, the individual GVW weights of the TV (& TT) do change in each CAT weigh... TV 1st weigh @ 6,140lbs, TV 2nd weigh @ 6,540lbs, TV 3rd weigh 6,740lbs. The TT GW weight increases between the 3rd weigh and 2nd weigh do to the weight being distributed back to the TT axles from the TV rear axle. The individual TV and TT GW's in the 2nd weigh are critical to compare to their respective specified GVWR's.

You are correct that only the TV's steering axle weight would ultimately remain the same between the 1st weigh and the 2nd weigh if the WDH was adjusted properly. And yes, the TV/TT GW between the 2nd weigh and 3rd weigh will remain the same .... plus/minus the CAT scale weight tolerances ("amabee's" reflects a 20lb tolerance delta).

Bob
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Old 02-25-2013, 09:05 AM   #9
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Quote:
I may be mis-interpreting your statement, please correct me if I'm wrong ...; for clarification the individual GVW weights of the TV (& TT) do in fact change in each CAT weigh... 1st weigh @ 6,140lbs ,2nd weigh @ 6,540lbs, 3rd weigh 6,740lbs. The TT weight changes as well between the 3rd and 2nd weighs do to the weight being distributed back to the TT axles.
Thanks, Bob, you're not mis-interpreting. That's why I asked for your comments. I was focused on getting the steering axle back to its original weight. I'm going to draw a diagram of the weights you mention in the snip so I can see the interaction there. That's how I have to do it.
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Old 02-25-2013, 09:14 AM   #10
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Hi Bob,

I have to agree that the last few posts here represent the best explanation of the effects of the WDH and answers questions with respect of the changes to the GVW's of the TV and the trailer. I also see that the amount of payload that is shifted from the TV to the TT represents a fairly significant % of the added Tongue weight. I have just ordered a set of Air-Lift 1000 air bags to fit into the coil springs of the Ram so that I can offset any rear end sag that the WDH doesn't address....what are your thoughts around this and how do these interact and with the WDH or do/can they in-fact address weight distribution without the WDH?

Quote:
Originally Posted by Rustic Eagle View Post
Anthe,

Nice detailed walk-thru using member "amabee's" CAT scale information (thank you "amabee") as an example on what information the CAT scale provides and the function of the WDH in conjunction with the CAT scale data.



I may be mis-interpreting your statement, please correct me if I'm wrong ...; For clarification, the individual GVW weights of the TV (& TT) do change in each CAT weigh... TV 1st weigh @ 6,140lbs, TV 2nd weigh @ 6,540lbs, TV 3rd weigh 6,740lbs. The TT weight changes as well between the 3rd weigh and 2nd weigh do to the weight being distributed back to the TT axles from the TV rear axle. The individual TV and TT GW's in the 2nd weigh are critical to compare to their respective specified GVWR's.

You are correct that only the TV's steering axle weight would ultimately remain the same between the 1st weigh and the 2nd weigh if the WDH was adjusted properly. And yes, the TV/TT GW between the 2nd weigh and 3rd weigh will remain the same .... plus/minus the CAT scale weight tolerances ("amabee's" reflects a 20lb tolerance delta).

Bob
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