WD Hitch effect on TW ratio

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

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

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.

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.

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

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 .

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.

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.

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

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.