WD Hitch effect on TW ratio

[DadoPax]

Lets run an example using easy #'s.

My trailer weights 1000lbs
My hitch weight is 100 lbs, or 10% of the overall trailer weight.
I put my trailer on a weight carrying hitch, 100lbs is carried by the hitch and 900 by the axles. The trailer goes down the road like it has a 10% tongue weight.

Introduce the weight distributing hitch...
Trailer hitch weight is still 100lbs but...
lets say the WDH distributes 50lbs to the rear axle of the trailer

HERE IS THE QUESTION...

Does the trailer still tow like it has 10% TW?
Or does it now tow LIKE it has 5% tongue weight because 950lbs is on the trailer axles and only 50lbs is on the tongue?

Thanks guys

[DadoPax]

mkirsch wrote:

DadoPax wrote:
HERE IS THE QUESTION...

Does the trailer still tow like it has 10% TW?
Or does it now tow LIKE it has 5% tongue weight because 950lbs is on the trailer axles and only 50lbs is on the tongue?

Thanks guys

It tows like it has 10% TW. The reason is because the physical mass is still in the same location.

This is a perfect answer. Thank you very much

[DadoPax]

joshuajim wrote:
I think you guys are over thinking this issue. Tongue weight is just a simplified number fof a center of gravity calculation. No matter what you do with a WDH the center of gravity remains the same and that is what primarily controls sway .

This makes sense,

Thank you

[drsteve]

The WD hitch does not change the tongue weight at all. It transfers load from the truck's rear axle to the front, and to the trailer axle. The amount transferred is a function of the spring bar rating.

[mkirsch]

DadoPax wrote:
HERE IS THE QUESTION...

Does the trailer still tow like it has 10% TW?
Or does it now tow LIKE it has 5% tongue weight because 950lbs is on the trailer axles and only 50lbs is on the tongue?

Thanks guys

It tows like it has 10% TW. The reason is because the physical mass is still in the same location.

[Wild_Card]

If you have 100#s of tongue weight you have 100# of tongue weight regardless of the hitch or how you have it adjusted.

[joshuajim]

I think you guys are over thinking this issue. Tongue weight is just a simplified number fof a center of gravity calculation. No matter what you do with a WDH the center of gravity remains the same and that is what primarily controls sway .

[handye9]

Concur with BarneyS.

Maybe this will help clear it up.

Put 1000 lb tongue weight on hitch without WD, it adds that 1000 lbs, plus the leverage on the tow vehicle (like a see-saw) removes a couple hundred pounds from the tow vehicles front axles, that weight is also added to the rear axle. End result, the center of gravity changes and the 1000 lb tongue weight is placing 13 - 1400 additional pounds on the rear axle of the tow vehicle.

Now apply WD. It reverses some of the leverage, moving weight both forward and back, restoring lost axle weight and center of gravity, increasing weight on trailer axles, and removing weight from tow vehicles rear axle.

Not all WD hitches will restore the same amount (percentage) to the front axles and different truck manufacturers recommend different amounts of front axle weight restoration. Some call for 100 percent, some call for 50 percent.

On my truck, the manual calls for fifty percent restoration of lost front axle weight. At 1000 lbs tongue weight, I could see scale weights showing something like this:

Note: These are ballpark numbers for demonstration purposes

without WD applied (tongue weight 1000 lbs)

front axle drops 300 lbs (compared to unhitched weight)
rear axle gains 1300 lbs (compared to unhitched weight)

with WD

150 lbs are restored to front axle
Rear axle weight gain is reduced to 1100 lbs
trailer axle gains 50 lbs

Weight gain on rear axle, even with WD applied, is actually more than the tongue weight. The added weight on the trailer axles, because it is directly on the axles, would have little to no effect on tongue weight.

As mentioned above, some hitches distribute more weight than others, the see-saw effect varies with different suspensions, vehicle center of gravity, wheel base lengths, and the WD effect on the trailer axles varies with tongue length, distance between tongue and axle, and trailer loading.

Another thing to note: Tongue weight is not a constant number. Depending on loading and usage of water, groceries, and holding tanks, it fluctuates during every trip. My tongue weight can fluctuate as much as 250 lbs.

[Bedlam]

When you are looking at tongue weight percentages, you are really looking at how the trailer weight is distributed fore and aft of the trailer axles. As long as this ratio remains the same, the trailer will track true with or without a WDH. Depending on your tow vehicle, you may or may not need a WDH hitch to redistribute some of that tongue weight off the rear vehicle axle. Get your tongue weight at 10-15 percent of actual trailer weight and it should track well.

[BarneyS]

The answer to your question is NO, the tongue weight will not change. In your example you would still have 12% tongue weight. The amount of weight felt by the tow vehicle will change but the actual tongue weight, and therefor the percent of tongue weight to total trailer weight, does not change nor does the tendency of the the trailer to sway due to tongue weight and balance change.

The only way to change the above would be to move the axles, load or move stuff in front of or behind the axles, or lengthen the tongue.
See the sticky at the top of this forum for more information.
Hope this helps.
Barney

[RinconVTR]

You want 10-15% tongue weight for any WDH system.

Once connected...the term tongue weight...forget about it.

I tow with an SUV that is actually the very scenario you mention. WITHOUT my WDH attached I exceed GVR and RAWR. With the WD attached, I am within all capacities. My own calculations told me I would be over spec regardless of WDH. But the scale says otherwise.

My actual tongue weight is 960lbs. My WDH has 1400lb bars and transfers 520lbs back to the front axle and almost 200lbs to the trailer. Moving 500+ off the rear axle to the front axle brings me well within rear axle spec and 200lbs to the trailer brings me more than 100lbs under GVR. (That's fully loaded, packed as we would for a long trip.)

There is no specific percentage nor calculation you can easily use to accurately estimate any given WDH with any given tow vehicle. There are far to many variables.

[LarryJM]

DadoPax wrote:
Maybe explaining the reason I ask will help everyone understand why I want to know.

Lets imagine you have a TT that has 12% of its weight on the hitch, and when you put that weight on your TV the trailer tracks right behind the truck straight and great. Only problem is... putting all that weight right on your rear axle creates a situation where you are over your axle rating. So you go get a WDH, move some of that weight to the front axle AND some of it to the rear axle of the TRAILER.

Do you no longer have 12% and straight and great due to the added load on the rear axles and the weight moved from the tongue?

The thing that confuses me is that people say WDH does not reduce the weight of the tongue, it simply relocates the places that weight travels to the ground. That makes sense.

I am confused about the effects this has on the 12%.

Hopefully my question makes sense?

A couple of points ....

1. TW if defined as what you would measure using something like a Sherline scale does not change.

2. W/O WDH the TW will increase the weight on the TV rear axle more than just the TW due to some of the front axle wt. being redistributed to the rear axle of the TV so a 1000lb TW might increase the rear axle TV wt. by 1100 to 1200.

3. With WDH the increase in wt. on the rear axle will become less with some redistributed to the front axle of the TV and some to the TT axle(s).

4. This is subject to debate, but some simply add the wt of the WDH system to the Cargo, but I think and believe it counts as TW with respect to the receiver TW rating. That is to say for a 1K TW receiver and a 100lb WDH system you can only have 900lb of TW as you would see on a Sherline scale until you reach the 1K TW limit on the TV receiver.

Larry

[wing_zealot]

Yes, it will decrease the weight on the rear axle. Yes it should still tow straight and great. I have no idea why it works if in essence it is no longer 12 percent.
Percent sign gone, now replies will work.

[DadoPax]

Maybe explaining the reason I ask will help everyone understand why I want to know.

Lets imagine you have a TT that has 12% of its weight on the hitch, and when you put that weight on your TV the trailer tracks right behind the truck straight and great. Only problem is... putting all that weight right on your rear axle creates a situation where you are over your axle rating. So you go get a WDH, move some of that weight to the front axle AND some of it to the rear axle of the TRAILER.

Do you no longer have 12% and straight and great due to the added load on the rear axles and the weight moved from the tongue?

The thing that confuses me is that people say WDH does not reduce the weight of the tongue, it simply relocates the places that weight travels to the ground. That makes sense.

I am confused about the effects this has on the 12%.

Hopefully my question makes sense?

[DadoPax]

Bedlam wrote:
You also have consider the distance from the hitch to the trailer front axle and from the hitch to the tow vehicle rear axle will most likely be different. If you take 50 percent of the tongue weight off the vehicle rear axle, that 50 percent may be distributed differently to the remaining axles based the difference in length. Although you figure this out mathematically, it is easier to find closed weigh station where the scale is still operating and try different WDH hitch settings and their effects on your combination.

These are made up numbers used to create a very easy to understand example.

In this HYPOTHETICAL situation, the variables create a situation where 50lbs is distributed to the rear axle.

The question is about the effects that distributed weight has on the ratio between tongue and axle weight.