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 > Tongue weight limits and wdh

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ktmrfs

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Posted: 08/25/22 10:22pm Link  |  Quote  |  Print  |  Notify Moderator

waynefi wrote:

What happens with the tongue weight limit when you are using a weight distributing hitch?

My Tacoma says the the tongue weight limit is 650 lbs. Does that mean that if my trailer has a tongue weight over 650 I need a wdh, or that I shouldn’t pull that trailer even with a wdh?

The function of a wdh is to take weight off the tongue, right? How would you even measure the tongue weight with the wdh in place?



WDH does NOT repeat NOT change the tongue weight. All it does is move weight from the truck rear axle to the truck front axle and trailer axles. If you look at the weights before and after of the axles the total will be the same. Therefore tongue weight hasn't changed.

Function of a WDH is NOT to take weight off the tongue, it is to move weight from the TV rear axle to the TV front axle and trailer axle.

Think of this experiment. you have a wheelbarrow loaded with stuff and you and the wheelbarrow are on a scale. You lift up on the handle does the overall weight change?? NO. the weight on the wheelbarrow front tire goes up, the weight on your feet goes up, the weight on the rear of the wheelbarrow feet goes down. Your arms are acting like the WD hitch.


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Mike134

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Posted: 08/26/22 05:36am Link  |  Quote  |  Print  |  Notify Moderator

ktmrfs wrote:

waynefi wrote:

What happens with the tongue weight limit when you are using a weight distributing hitch?

My Tacoma says the the tongue weight limit is 650 lbs. Does that mean that if my trailer has a tongue weight over 650 I need a wdh, or that I shouldn’t pull that trailer even with a wdh?

The function of a wdh is to take weight off the tongue, right? How would you even measure the tongue weight with the wdh in place?



WDH does NOT repeat NOT change the tongue weight. All it does is move weight from the truck rear axle to the truck front axle and trailer axles. If you look at the weights before and after of the axles the total will be the same. Therefore tongue weight hasn't changed.

Function of a WDH is NOT to take weight off the tongue, it is to move weight from the TV rear axle to the TV front axle and trailer axle.

Think of this experiment. you have a wheelbarrow loaded with stuff and you and the wheelbarrow are on a scale. You lift up on the handle does the overall weight change?? NO. the weight on the wheelbarrow front tire goes up, the weight on your feet goes up, the weight on the rear of the wheelbarrow feet goes down. Your arms are acting like the WD hitch.


My cat scale tickets show 200lbs removed from my truck and put onto the trailer axles when the spring bars are connected. So while the tongue weight itself doesn't change the apparent tongue weight that the truck feels does get moved


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valhalla360

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Posted: 08/26/22 06:17am Link  |  Quote  |  Print  |  Notify Moderator

blt2ski wrote:

10% is a common hitch wieght recommendation for a ball/pintle mount trailer. 15% is typical max %.


15% isn't a max desirable. The issue is most trucks run out of hitch weight capability at or before 15% is reached.

5th wheels tow great at 20-25%. Semis are more like 50% (depends on loading).


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Posted: 08/26/22 06:27am Link  |  Quote  |  Print  |  Notify Moderator

ktmrfs wrote:


WDH does NOT repeat NOT change the tongue weight. All it does is move weight from the truck rear axle to the truck front axle and trailer axles. If you look at the weights before and after of the axles the total will be the same. Therefore tongue weight hasn't changed.

Function of a WDH is NOT to take weight off the tongue, it is to move weight from the TV rear axle to the TV front axle and trailer axle.

Think of this experiment. you have a wheelbarrow loaded with stuff and you and the wheelbarrow are on a scale. You lift up on the handle does the overall weight change?? NO. the weight on the wheelbarrow front tire goes up, the weight on your feet goes up, the weight on the rear of the wheelbarrow feet goes down. Your arms are acting like the WD hitch.


Actually, yes, it does reduce the tongue weight. It's not the purpose as you indicate but it is a side effect.

Your wheelbarrow analogy is incorrect. Since your wrists are points of rotation, they do not have a similar effect to a WDH.

Go down to a CAT scale and weigh with and without the hitch connected. I'll put down $100 with 10-1 odds in your favor that the trailer axle weights increase when the WDH is connected.

Think of it this way. The bars are locked into the truck hitch (and frame). The bars push down on the trailer A-frame. Since the ball is a pivot point it can only push up. It can't apply a moment arm. The bar connection is behind ball by a couple feet. Since the ball can't resist the moment created by that 2ft lever arm...Some of that downward force must be carried by the trailer axles of the trailer would begin rotating down.

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Posted: 08/26/22 07:05am Link  |  Quote  |  Print  |  Notify Moderator

Dont forget the weight of the wdh has to be added into the equation also. Weight is weight, it needs to be factored in.


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waynefi

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Posted: 08/26/22 08:56am Link  |  Quote  |  Print  |  Notify Moderator

Here’s my guess about how the limits work:

Putting weight on the hitch does two things. It adds weight to the TV, and it takes weight off of the front axle. The payload limit tells whether you have added too much weight. The tongue weight limit tells if you have taken too much weight off the front axle. A WDH hitch helps with the front axle weight.

So if a CAT scale tells you that the gross vehicle weight is within limits, the rear axle weight is within limits, and the front axle weight is close to what it was without the trailer, you’re OK.


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Posted: 08/26/22 09:02am Link  |  Quote  |  Print  |  Notify Moderator

Why are you and tealboy hand wringing over little trailers?
Trust me, I know you're also just trying to understand the effects of trailer hitch weight, but the ratings do that for folks who have trouble visualizing or understanding it.
What you're hypothetically proposing with your truck is also fine, within the hitch weight.
Get heavier hitch weight than that and you won't like towing with the Taco. Simple as that.


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ktmrfs

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Posted: 08/26/22 09:53am Link  |  Quote  |  Print  |  Notify Moderator

Mike134 wrote:

ktmrfs wrote:

waynefi wrote:

What happens with the tongue weight limit when you are using a weight distributing hitch?

My Tacoma says the the tongue weight limit is 650 lbs. Does that mean that if my trailer has a tongue weight over 650 I need a wdh, or that I shouldn’t pull that trailer even with a wdh?

The function of a wdh is to take weight off the tongue, right? How would you even measure the tongue weight with the wdh in place?



WDH does NOT repeat NOT change the tongue weight. All it does is move weight from the truck rear axle to the truck front axle and trailer axles. If you look at the weights before and after of the axles the total will be the same. Therefore tongue weight hasn't changed.

Function of a WDH is NOT to take weight off the tongue, it is to move weight from the TV rear axle to the TV front axle and trailer axle.

Think of this experiment. you have a wheelbarrow loaded with stuff and you and the wheelbarrow are on a scale. You lift up on the handle does the overall weight change?? NO. the weight on the wheelbarrow front tire goes up, the weight on your feet goes up, the weight on the rear of the wheelbarrow feet goes down. Your arms are acting like the WD hitch.


My cat scale tickets show 200lbs removed from my truck and put onto the trailer axles when the spring bars are connected. So while the tongue weight itself doesn't change the apparent tongue weight that the truck feels does get moved


correct. And your experience is similar to mine. But it doesn't change the weight limit on the receiver.

ktmrfs

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Posted: 08/26/22 09:58am Link  |  Quote  |  Print  |  Notify Moderator

valhalla360 wrote:

ktmrfs wrote:


WDH does NOT repeat NOT change the tongue weight. All it does is move weight from the truck rear axle to the truck front axle and trailer axles. If you look at the weights before and after of the axles the total will be the same. Therefore tongue weight hasn't changed.

Function of a WDH is NOT to take weight off the tongue, it is to move weight from the TV rear axle to the TV front axle and trailer axle.

Think of this experiment. you have a wheelbarrow loaded with stuff and you and the wheelbarrow are on a scale. You lift up on the handle does the overall weight change?? NO. the weight on the wheelbarrow front tire goes up, the weight on your feet goes up, the weight on the rear of the wheelbarrow feet goes down. Your arms are acting like the WD hitch.


Actually, yes, it does reduce the tongue weight. It's not the purpose as you indicate but it is a side effect.

Your wheelbarrow analogy is incorrect. Since your wrists are points of rotation, they do not have a similar effect to a WDH.

Go down to a CAT scale and weigh with and without the hitch connected. I'll put down $100 with 10-1 odds in your favor that the trailer axle weights increase when the WDH is connected.

Think of it this way. The bars are locked into the truck hitch (and frame). The bars push down on the trailer A-frame. Since the ball is a pivot point it can only push up. It can't apply a moment arm. The bar connection is behind ball by a couple feet. Since the ball can't resist the moment created by that 2ft lever arm...Some of that downward force must be carried by the trailer axles of the trailer would begin rotating down.


Agreed that the trailer axle weights go up, as does the TV front axle and the truck rear axle weight goes down. But the sum of the three axle weights stays the same That means the tongue weight hasn't changed. Now since many scale weights have a 25 or 50lb increment that may cause a slight difference but it is due to scale resolution.

If the tongue weight changes then that force needs to be accounted for in the force on the TV and trailer axles. If the tongue weight goes down, then the sum of the weight on the other axles must go up to account for it.

Now, if the tongue was nose down w/o wd and now level, there could be a slight decrease in tongue weight due to the trailer attitude which would show up in the weight calculations. But it is going to be minor.

* This post was edited 08/26/22 10:49am by ktmrfs *

valhalla360

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Posted: 08/26/22 10:55am Link  |  Quote  |  Print  |  Notify Moderator

ktmrfs wrote:

Agreed that the trailer axle weights go up, as does the TV front axle and the truck rear axle weight goes down. But the sum of the three axle weights stays the same That means the tongue weight hasn't changed. Now since many scale weights have a 25 or 50lb increment that may cause a slight difference but it is due to scale resolution.

If the tongue weight changes then that force needs to be accounted for in the force on the TV and trailer axles. If the tongue weight goes down, then the sum of the weight on the other axles must go up to account for it.

Now, if the tongue was nose down w/o wd and now level, there could be a slight decrease in tongue weight due to the trailer attitude which would show up in the weight calculations. But it is going to be minor.


Umm..no

The WDH moves some of the tongue weight back onto the trailer axles.

Nose up or down, doesn't impact the weights enough to notice.

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