Tongue weight limits and wdh

[waynefi]

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?

My current trailer has a nominal tongue weight of 380, but that is before water, a second battery, etc.

[valhalla360]

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.

[ktmrfs]

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.

[ktmrfs]

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.

[Grit_dog]

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.

[waynefi]

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.

[Sjm9911]

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

[valhalla360]

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.

[valhalla360]

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).

[Mike134]

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

[ktmrfs]

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.

[blt2ski]

10% is a common hitch wieght recommendation for a ball/pintle mount trailer. 15% is typical max %.
In Europe, typical HW minimum is 7-8%, boats sometimes 7-8 also.
Using a lower hw% is better for a max trailer you can pull, assuming rated for that amount or not. 15% of 650 is 975 lbs of HW for the same 6500 lb trailer. If a 5W, 20-25% is recommended, so1300-1625 lbs is needed for a 6500 lb trailer. Quite possibly the next chassis sized larger truck!
It comes down to a game of numbers, from multiple angles, deciding which numbers you really should follow, vs good idea to follow.

Marty

[waynefi]

The 650 pound limit came from Toyota, so it’s not a limit on the ball mount, etc. It is either the hitch receiver or something about the stability of the vehicle.

I always thought it was about taking too much weight off of the front wheels.

Here’s another part of the mystery. The Tacoma’s tow capacity is 6500, the tongue weight limit is 650, exactly 10%. A lot of trucks have that 10% value. Why?

[blt2ski]

IF the 650 is the hitch rating, you have say 700. Get rid of that hitch, put a heavier duty one on.

If that 650 is max per owners manual, that can be a different ball in this game of what one can do or not do towing wise.

If OM states say 1000 lbs, hitch is rated for 650, do my option one, replace it!

Marty

[rjstractor]

waynefi wrote:
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?

Well, sort of. A wdh transfers load from the hitch ball itself onto the front axle of the tow vehicle and also the trailer axles. Without a bunch of crazy, indecipherable calculations, the only way to really know for sure is to weigh truck and trailer axles before and after wdh hookup. I don't know if the 650 lbs for the Taco is with or without wdh, but it does seem like although Toyota makes tough trucks, the US market ones have soft, squishy springs that probably just about bottom out with 650 pounds right on the hitch.

[Mike134]

my '19 F150 has 2 ratings
500lbs if just a ball
1300lbs if using a WDH

Calculated weight on the hitch using the 3 pass cat scale method I'm running at 1100 lbs.