WD Hitch Weight % Transferred

[kgarrett9999]

Obviously, the answer to my question is going to depend, but what is a good rule of thumb to use when estimating how much weight a WD Hitch will transfer from the hitch?

Another thread recently suggested an estimate of 20-25%.

[kgarrett9999]

I know this is an old thread, but I did finally purchase the new travel trailer.

I rarely travel with fluids fresh, gray or black so that shouldn't be a factor. I think I'm over estimating the weight of stuff I'll add to the trailer but I expect it to grow over time.

The numbers below are tight but I'm hoping that the WDH actually transfers more than the 10% that seems to be the bottom end of the expected weight transfer to the trailer axle.

5755 Dry Weight
835 Tongue Weight
1000 Estimated Stuff

1453 Payload
-430 Fat Butts
-50 Dogs
-80 WDH
-980 Estimated Loaded Tongue Weight
98 Hitch transfer to trailer axle (10%)

11 Remaining payload


Now I wish that I had gotten the HD Payload option, but I couldn't find a truck equipped the way I wanted with that option in the color that my wife wanted anywhere in the US at the time.

[kgarrett9999]

Ooops...I stepped away from the keyboard for a few days or I could have resolved this. Yes, I understand that I need to add in the WDH, but also understand that it isn't a wash with the weight transferred to the TT axles.
Actually I do currently have a trailer with a minimal hitch weight that could actually easily be towed without WDH. I am in the market for a new TT and was really just wanting to roughly estimate what my pickup could handle when I'm looking at all the different offerings in the marketplace. Some of them I can eliminate automatically because I know for sure they will cause me to exceed the allowable load on my TV and some I know for sure are light enough that it won't be a problem. It is for those in between that I was looking for a rule of thumb to apply to see if I'm close enough to even bother really sitting down and running all the numbers.

Of course the really hard part is until I actually hook up the TT to my TV, load it with my camping gear and take it to the scales I won't know for sure.

Still not sure that I have a good rule of thumb to use, but it looks like 10-25% hitch weight transfer to the TT axles seems like a good range.

I like to be conservative, so to tell the truth I'll probably end up with a TT that doesn't exceed my available capacity without the WDH and allow the WDH to give me the 10-25% margin that I feel comfortable with. And as previously noted, I will allow that transfer to help cover the weight of the hitch itself which I guess I should go weigh when I get a chance because I'm pretty sure it don't weigh a 100 lbs like I keep seeing used here. Shipping weight (including packaging, etc) on several of the WDH's that I just
googled were between 50 and 75 lbs. I know it isn't a lot, but 25-50 lbs would cover the weight of one of the dogs and a kennel.

[Campin_LI]

Ron Gratz wrote:

Campin LI wrote:
---My guess (assumption using fictitious numbers)is that he is looking at a trailer with say 900 lbs tongue weight but only has 700 lbs available in the truck. That being said if 200 lbs is transferred to the trailer axles, he is thinking he is good to go. All I am saying is that if this is how he is looking at the issue, the weight of the WDH sort of cancels out the transferred weight and the tongue weight is exactly what it is. If I'm assuming his intention wrong then disregard what I wrote.

A poster's intentions often can be ascertained by reading some of his/her recent posts on other threads.

In this post, the OP states:

---My assumption is that with my wife and I plus a dog or two and their kennels plus a couple of bicycles plus WD hitch, we have somewhere around 850-900 lbs available for hitch weight.

(bold and underline added for emphasis)

The OP is properly accounting for the weight of the WDH -- by including it as part of the TV's cargo.
By doing so, he can properly benefit from the difference between "tongue weight" and "hitch load" when WD is applied.

Hence, his question: "what is a good rule of thumb to use when estimating how much weight a WD Hitch will transfer from the hitch?"

Ron

I am guilty of not looking back at the OP's old posts so please disregard my posts as I stated above. Technically though, the OP did start the sentence by saying "My assumption", so he is estimating anyway. Since he is estimating his WDH hitch weight, he can estimate the amount transferred to the travel trailer wheels.

The only point I want to make is that if you spend too much time estimating all your weights, even if you don't mean to, you will always estimate in favor of what you are looking to achieve. The I always pack light is the worst estimation anyone can make. When we sold our first trailer, I could not believe how much stuff we had to take out of it:)

[Ron_Gratz]

Campin LI wrote:
---My guess (assumption using fictitious numbers)is that he is looking at a trailer with say 900 lbs tongue weight but only has 700 lbs available in the truck. That being said if 200 lbs is transferred to the trailer axles, he is thinking he is good to go. All I am saying is that if this is how he is looking at the issue, the weight of the WDH sort of cancels out the transferred weight and the tongue weight is exactly what it is. If I'm assuming his intention wrong then disregard what I wrote.

A poster's intentions often can be ascertained by reading some of his/her recent posts on other threads.

In this post, the OP states:

---My assumption is that with my wife and I plus a dog or two and their kennels plus a couple of bicycles plus WD hitch, we have somewhere around 850-900 lbs available for hitch weight.

(bold and underline added for emphasis)

The OP is properly accounting for the weight of the WDH -- by including it as part of the TV's cargo.
By doing so, he can properly benefit from the difference between "tongue weight" and "hitch load" when WD is applied.

Hence, his question: "what is a good rule of thumb to use when estimating how much weight a WD Hitch will transfer from the hitch?"

Ron

[Campin_LI]

Ron Gratz wrote:

Campin LI wrote:
I understand what you are trying to do. You have to realize that your weight distribution hitch has it's own weight. The weight of the hitch is about the same (give or take) as the weight that will be transferred to the trailer axles once setup. Therefore, in my opinion, there is no substantial gain in truck capacity to your train of thought.---

A typical WDH probably weighs less than 100#, while load transfers to the TT can exceed 300#.
IMO, neither the weight of the WDH nor the amount of load transfer to the TT should be ignored.

IMO, a proper load analysis procedure should include the actual or estimated weight of the WDH as TV cargo.
The TV's unhitched GVW should include the weight of TV, occupants, added equipment, cargo, and the WDH.
Then, the TV's GVWR minus the GVW gives the maximum vertical load which can be imposed on the hitch.

Example:

If the TV's GVW (including weight of WDH) is 6200# and the GVWR is 7000#, you have 800# remaining for vertical load on hitch.
A 1000# TW, with 200# transferred to TT's axles, will exert 800# on the hitch.

If you don't include the 100# weight of WDH in the TV's GVW, the GVW will be 6100#, and you will have 900# remaining for combined weight of WDH plus vertical load exerted on the hitch.
The result is the same -- you can still have 800# exerted on the hitch. And that means you can still have 1000# of TW if 200# is transferred to the TT's axles.

If you ignore both the weight of the WDH and the load transfer to the TT, you'll incorrectly calculate an allowable "tongue weight" of 900#.

At a TW% of 12.5%, the difference between an allowable TW of 900# and 1000# means an increase in allowable TT weight of 800#.

Ron

I understand what you are saying, but my assumption is that the OP's question is simpler and based on estimation (he does not have a trailer) and the question appears to relate to payload capacity of his existing truck (how much tongue weight can he carry), not how much the trailer weighs. I still believe that as far as estimation goes, the amount of weight theoretically transferred to the trailer axles by use of a WDH is "about" the same as the weight of the WDH itself (which counts as payload capacity). If the OP ignores both factors, he will know "about" how much tongue weight he can handle. After all, he is going by brochure weights anyway so even though the "actual" amount of weight transferred to the trailer axle is likely more than the weight of the WDH, as far as estimating goes, not accounting for that weight helps in dealing with actual tongue weight which will likely increase every year because we keep adding more and more stuff into our trailers year after year anyway:)

To clarify, my guess is that the OP is looking to figure out how much tongue weight he can handle in his truck and wants to right off some of that tongue weight as transferred to the trailer axles using a WDH so that he can carry more tongue weight. My guess (assumption using fictitious numbers)is that he is looking at a trailer with say 900 lbs tongue weight but only has 700 lbs available in the truck. That being said if 200 lbs is transferred to the trailer axles, he is thinking he is good to go. All I am saying is that if this is how he is looking at the issue, the weight of the WDH sort of cancels out the transferred weight and the tongue weight is exactly what it is. If I'm assuming his intention wrong then disregard what I wrote.

[Ron_Gratz]

Campin LI wrote:
I understand what you are trying to do. You have to realize that your weight distribution hitch has it's own weight. The weight of the hitch is about the same (give or take) as the weight that will be transferred to the trailer axles once setup. Therefore, in my opinion, there is no substantial gain in truck capacity to your train of thought.---

A typical WDH probably weighs less than 100#, while load transfers to the TT can exceed 300#.
IMO, neither the weight of the WDH nor the amount of load transfer to the TT should be ignored.

IMO, a proper load analysis procedure should include the actual or estimated weight of the WDH as TV cargo.
The TV's unhitched GVW should include the weight of TV, occupants, added equipment, cargo, and the WDH.
Then, the TV's GVWR minus the GVW gives the maximum vertical load which can be imposed on the hitch.

Example:

If the TV's GVW (including weight of WDH) is 6200# and the GVWR is 7000#, you have 800# remaining for vertical load on hitch.
A 1000# TW, with 200# transferred to TT's axles, will exert 800# on the hitch.

If you don't include the 100# weight of WDH in the TV's GVW, the GVW will be 6100#, and you will have 900# remaining for combined weight of WDH plus vertical load exerted on the hitch.
The result is the same -- you can still have 800# exerted on the hitch. And that means you can still have 1000# of TW if 200# is transferred to the TT's axles.

If you ignore both the weight of the WDH and the load transfer to the TT, you'll incorrectly calculate an allowable "tongue weight" of 900#.

At a TW% of 12.5%, the difference between an allowable TW of 900# and 1000# means an increase in allowable TT weight of 800#.

Ron

[Ron_Gratz]

xcntrk wrote:

Ron Gratz wrote:
Your example shows, for no WD,
the steer axle lost 3200-3040 = 160# and
the drive axle gained 3880-2840 = 1040#.

With no WD, I would expect the steer axle to lose an amount equal to about 40-50% of the 880# TW and the drive to gain about 140-150% -- depending on TV wheelbase and ball overhang.
How did you calculate the front axle loss and the rear axle gain?

Those are real CAT scale weights captured from another user here (empty TV, loaded TT w/no WD, and loaded TT w/WD) each individually measured.

Thanks for the link to the source of the weight values which you entered into your spreadsheet. Posts #1 and #5 clear up the mystery about the steer and drive axle load changes.

Post #1 says the tongue weight as measured by Sherline is ~650# (rather than 880#).
Post #5 says that the front & rear unhitched loads of 3200 & 2840 were from a previous weighing which did not include dogs and kennels.
Unhitched individual axle loads were not measured during the later weighing, but the TV GVW was 6270# instead of 6040#.

Assuming TW = 650#, wheelbase = 157", and ball overhang = 61" would cause approximately 250# removed from the steer axle and 900# added to the drive axle.
This indicates the unhitched steer axle load should be around 3040+250 = 3290#
and the unhitched drive axle load should be around 3880-900 = 2980#,
adding up to the reported GVW of 6270#.

With WD applied, the steer axle would have lost 10# relative to unhitched while the drive axle gained 540#.
The front axle load restoration was close to 100%.

xcntrk wrote:
With this user's numbers and WD enabled, 240# came off the rear axle and went back to the front axle, and 140# came off the rear axle and went back to the TT axles, for a total of 360# total distributed due to the WD hitch. Percentage wise you could say 41% of the TW was redistributed by the WD hitch (including both TV and TT weight changes), but I don't call that percentile out in my spreadsheet because a large portion of it still remains on the TV (just moved from rear to front). This is where the 14% comes from; the 104# that went back to the TT axles or 14% of the original TW.

If you used 104# -- that value should have been 140#. And, the TW should have been 650# rather than 880#.
This would mean the transfer to the TT's axles was approximately 140/650 = 22% of TW.

Ron

[Campin_LI]

I understand what you are trying to do. You have to realize that your weight distribution hitch has it's own weight. The weight of the hitch is about the same (give or take) as the weight that will be transferred to the trailer axles once setup. Therefore, in my opinion, there is no substantial gain in truck capacity to your train of thought. Example, If your weight distribution hitch weighs 100 lbs and you adjust the hitch to transfer 130 lbs to the trailer axles, you have only redistributed 30 lbs away from the truck because the hitch itself added payload weight. Since you are estimating, in my opinion, it's a variable that should be ignored.

[kgarrett9999]

Thanks for all the great replies.

Obviously I knew that it would depend, but was really just looking for a "rule of thumb" to aid in selecting a new travel trailer.

Based on all the numbers thrown around, it looks like it can vary from approximately 15-25%.

Bottom line is I feel comfortable that if my hitch weight doesn't cause me to exceed my numbers without the WD hitch, then a WD hitch will give me an additional 15-25% margin of safety. And if a particular TT puts me over my numbers without the WD hitch, then I need to actually do the calculations with real numbers.

Again, thanks for the info.

[xcntrk]

Ron Gratz wrote:

xcntrk wrote:
Here's an example:

Your example shows, for no WD,
the steer axle lost 3200-3040 = 160# and
the drive axle gained 3880-2840 = 1040#.

With no WD, I would expect the steer axle to lose an amount equal to about 40-50% of the 880# TW and the drive to gain about 140-150% -- depending on TV wheelbase and ball overhang.
How did you calculate the front axle loss and the rear axle gain?

Also, the bottom line shows TW Redistributed = 14% w/WD.
How is that value calculated?

Ron

Those are real CAT scale weights captured from another user here (empty TV, loaded TT w/no WD, and loaded TT w/WD) each individually measured. With this user's numbers and WD enabled, 240# came off the rear axle and went back to the front axle, and 140# came off the rear axle and went back to the TT axles, for a total of 360# total distributed due to the WD hitch. Percentage wise you could say 41% of the TW was redistributed by the WD hitch (including both TV and TT weight changes), but I don't call that percentile out in my spreadsheet because a large portion of it still remains on the TV (just moved from rear to front). This is where the 14% comes from; the 104# that went back to the TT axles or 14% of the original TW.

[gmw_photos]

^^^^^^ ....uh.....ok, thanks Ron ! You have given me something think about this afternoon as I sit here and stare at the truck and hitch. I think it's going to take me a little while to wrap my head around all that. 😄

[Ron_Gratz]

gmw photos wrote:
---I have 600 pounds of tongue weight. When the trailer is just on the ball, with no weight distribution, my steer axle loses 300 pounds. I set my WD hitch to restore that 300 pounds to the steer axle, and in doing that, it also increases the load on the trailer axle by 140 pounds.---

Thanks for the numbers. It's good to see that your 23% of TW transferred to the TT axles agrees well with theory.

As others have stated, the vertical force on the ball remains 600 pounds.---

Perhaps you mean vertical force on the hitch?

With WD applied the vertical force on the ball becomes equal to the tongue weight
PLUS the downward force exerted on the A-frame by the two WD bars
MINUS the load transferred to the TT's axles.

In your case, the vertical force on the ball might be 600+1000-140 = 1460#.
The front ends of the WD bars would be pushing upward against the bottom of the hitch head with a force of 1000#.
The net downward force on the hitch then is 1460-1000 = 460# -- which is equal to the tongue weight MINUS the load transferred to the TT's axles.

So, with WD applied, the vertical force on the hitch (and the vertical load on the TV) is decreased by the amount of load transferred to the TT's axles.

Ron

[jmtandem]

The fairly simple relationship is: TW% = FALR% * D2/(D2+D3)

where TW% is percent of TW transferred to TT's axles
and FALR% is load restored to front axle divided by load removed from front axle.

For example, if D2 = 65", D3 = 195", and FALR% = 100%: TW% = 100% * 65(65+195) = 25%

For the above dimensions, if you wish to restore only 75% of front axle load, TW% is 18.75%.
If you wish to restore 125% of front axle load, the theoretical TW% is 31.25%.

Given the actual values for D2 and D3 and your desired FALR%, you can calculate your own value for the required percentage of TW transferred to the TT's axles.

The short answer to your question -- 20% is a pretty good rule of thumb.

Ron,

Thanks for the formula. I appreciate it.

[gmw_photos]

To the OP, not sure if this is what you are asking, but as an example, this is what my numbers are for my camper. I have 600 pounds of tongue weight. When the trailer is just on the ball, with no weight distribution, my steer axle loses 300 pounds. I set my WD hitch to restore that 300 pounds to the steer axle, and in doing that, it also increases the load on the trailer axle by 140 pounds. So a total 440 pounds of tongue weight gets re-distributed.

As others have stated, the vertical force on the ball remains 600 pounds. Without WD I am effectively heavy in the "center" ( rear axle of the truck) of the combined rig. With WD I am more "balanced" because the action of the weight bars has effectively rotated the truck frame forward, as seen by the weight restoration on the steer axle. It has also rotated the trailer frame backward, again as seen by the increase in weight on the trailer axles.