Tongue Weight Calculation

[Brian B-P]

Originally Posted by TTMartin

While I don't disagree that there is some lever created by more weight being carried on the front axle if the trailer is nose low.

Tongue weight is dynamic based on trailer loading, so without knowing where everything is loaded in the trailer, there is no way to know for sure what a a possible tongue weight might be.

But it is absolutely certain that without the WD spring bars engaged, and with the ball height setting unchanged, the tongue will be lower than normal.

[Greatboatz3]

I guess I'm not sure how to measure tongue weight. The main point I picked up is that:
Tongue weight is dynamic in that in can change relative to where weight is placed in or on the trailer and that use of a WDH does not change the tongue weight.

If that is true can the Tongue be determined strictly by placing a scale under the jack , leveling the trailer putting the WDH bars on the trailer in there approximate locations.

Questions: Does weight added to the tow vehicle aft of the rear trailer effect the tongue weight?
What is the effect of the weight in that location?

[Brian B-P]

Originally Posted by Greatboatz3

The main point I picked up is that:
Tongue weight is dynamic in that in can change relative to where weight is placed in or on the trailer and that use of a WDH does not change the tongue weight.

Right

Originally Posted by Greatboatz3

If that is true can the Tongue be determined strictly by placing a scale under the jack , leveling the trailer putting the WDH bars on the trailer in there approximate locations.

Yes, but the weight measured at the jack will be a few percent higher than the true tongue weight (which would be measured at the ball location of the coupler).

While the WDH spring bars add to the weight carried by the hitch, if your concern is the weight distribution of the trailer they are not relevant - just leave them off.

Originally Posted by Greatboatz3

Questions: Does weight added to the tow vehicle aft of the rear trailer effect the tongue weight?
What is the effect of the weight in that location?

If it is in the tow vehicle, it isn't part of the trailer and isn't tongue weight. If it is carried by the tow vehicle and not mounted to the hitch, it isn't hitch weight. It does have a similar effect on the axle loading and handling of the tow vehicle as hitch weight.

[Greatboatz3]

Thank you Brian,
I guess I can place a 4x4 of the correct length under the coupler then retract the jack to get a more accurate reading
As getting the tongue weight right is critical to handling I'll purchase a 550 pound
bathroom scale. What is preferable 10% or 15% of the trailer weight?

[dlakeman]

The actual (via a 550lb scale) weight of my 21C taken minutes ago on the electric jack square base resting on the scale is 512lbs. There aren't any changes to trailer since I weighed the truck and trailer at the CAT scale. WDH bars not attached to trailer. Trailer not attached to truck, and trailer in level position as when I tow. Empty tanks. I realize the jack based is rearward of the hitch coupler, which affects the actual tongue weight, however the scale reading is significantly heavier than the calculated weighs from the CAT scale discussed on this threat.

[Brian B-P]

Originally Posted by dlakeman

The actual (via a 550lb scale) weight of my 21C taken minutes ago on the electric jack square base resting on the scale is 512lbs.

Excellent. That happens to match the guess that I put in my example, and it's reasonable for a trailer of this size.

Originally Posted by dlakeman

I realize the jack based is rearward of the hitch coupler, which affects the actual tongue weight, however the scale reading is significantly heavier than the calculated weighs from the CAT scale discussed on this threat.

Right... because the tongue height is now correct.

To compensate for the jack position, find the distance from the ball position to the midpoint between the axle lines, and from the jack to the same point. The ratio of the distances is the same aa the ratio of the scale reading and tongue weight.

Also, scale weights typically have 20-poind precision, and combining multiple readings accumulates error, so determining tongue weight from scale readings of axle weights works, but yields an approximate result. That 360 pounds is a rough number.

[gklott]

Recommend using the Escapees SmartWeigh. This was our result loaded as we usually travel. It matched closely what we got on a Flying J CAT scale several months earlier.

73/gus

[dlakeman]

Originally Posted by gklott

Recommend using the Escapees SmartWeigh. This was our result loaded as we usually travel. It matched closely what we got on a Flying J CAT scale several months earlier.

73/gus

Don't you have to be in Texas or Florida? Seems SmartWeigh is only in those two States, and in only one city in each State.

[Centex]

Thanks for posting your SmartWeigh sheet, Gus.

Not at all suggesting there's anything 'worrisome' about it but the hitched +50# right front vs -25# left front is interesting to me; not that there's weight transfer at the TV front wheels but that the amount of transfer is different side-to-side, especially that one side is 'negative' change and one 'positive'.

Just curious if there's any notion why / how that occurs?

Is your "with trailer" configuration also 'with WDH'?

Again, nothing worrisome, just interesting, piqued the curiosity.

[gklott]

Originally Posted by dlakeman

Don't you have to be in Texas or Florida? Seems SmartWeigh is only in those two States, and in only one city in each State.

We did ours in AZ. Recommend checking the site for the locations,

73/gus

[gklott]

Originally Posted by Centex

Not at all suggesting there's anything 'worrisome' about it but the hitched +50# right front vs -25# left front is interesting to me; not that there's weight transfer at the TV front wheels but that the amount of transfer is different side-to-side, especially that one side is 'negative' change and one 'positive'. Just curious if there's any notion why / how that occurs? Is your "with trailer" configuration also 'with WDH'? Again, nothing worrisome, just interesting, piques the curiosity.

Hitched weight is as we tow, with our Hensley WD hitch, with jacks adjusted for the ride we like. That's what SmartWeigh asks you to do - as you normally tow.

They record weights in 25 lb. increments, which could be one difference. Don't know their rounding rule. Otherwise, and I am not sure why we got the small left-to-right difference.

We got a "Gold Star" for being so closely balanced!

Plan to do another SmartWeigh on next trip after replacing the two Lifeline GPL-4CT 6V AGM batteries in tongue box with four BattleBorn GC2 12V batteries under the front dinette bench seats. We are also adding our Sprinter 2500 as the tow vehicle.

73/gus

[cpaharley2008]

I had the advantage of having a new Escape and the person who wanted to see it worked at a Montana weight stop. So on the trip home from Osoyoos, I showed him the trailer and got weighed,,,,,,,,,,he bought one!

[dlakeman]

Originally Posted by gklott

We did ours in AZ. Recommend checking the site for the locations,

73/gus

I checked the website before I posted. Only 2 cities listed.

[Brian B-P]

Originally Posted by Centex

Not at all suggesting there's anything 'worrisome' about it but the hitched +50# right front vs -25# left front is interesting to me; not that there's weight transfer at the TV front wheels but that the amount of transfer is different side-to-side....

Although with the 25-pound reading precision the difference isn't huge, it does suggest that one side of the WD is tighter than the other side, twisting the truck relative to the trailer.

The WD also might be over-applied - the "with trailer and WD" front axle load should never be more than the "without trailer" load - but again within scale precision the readings don't clearly show that.

I think the trailer readings are potentially of more concern: the left total and right total are not quite the same but there is no significant difference and even a moderate difference would be okay; however, there is a moderately significant diagonal difference. That may be due to a twisted trailer frame, or unequal suspension wear, or just unmatched tire pressures, or nothing but the area used for the measurement being not perfectly flat.


It is interesting - especially in this thread about tongue weight - that Escapees doesn't even attempt to determine tongue weight. They are set up to make the measurements as quickly and easily as possible, checking only the as-operated condition of the tire loads.

[gklott]

Originally Posted by dlakeman

I checked the website before I posted. Only 2 cities listed.

Yes, sad to see that the AZ site closed 2 months ago. It is well worth a detour should you be traveling through TX and FL.

73/gus

[gklott]

Originally Posted by Brian B-P

I think the trailer readings are potentially of more concern: the left total and right total are not quite the same but there is no significant difference and even a moderate difference would be okay; however, there is a moderately significant diagonal difference. That may be due to a twisted trailer frame, or unequal suspension wear, or just unmatched tire pressures, or nothing but the area used for the measurement being not perfectly flat.

Not sure I would apply "moderately significant" to a difference on the order of ≤ 3%. Filling our fresh water tank, not dumping gray water, or picking up groceries could cause this scale of change.

Would anyone else care to share their SmartWeigh results?

73/gus

[Brian B-P]

Originally Posted by gklott

Not sure I would apply "moderately significant" to a difference on the order of ≤ 3%. Filling our fresh water tank, not dumping gray water, or picking up groceries could cause this scale of change.

Loading differences can change the total weight or tongue weight or side-to-side difference a few percent and that's not an issue. I was referring to the diagonal bias, which should always be nearly zero... and it probably still isn't an issue.