Weight distribution and sway control hitch not allowed

[out of sight]

I saw this on the U-Hail website:

Weight distributing or sway control devices ARE NOT USED for towing U-Haul trailers. Towing a properly loaded U-Haul trailer does not require these devices. These devices may have a negative effect on vehicle handling and braking and may restrict the operation of the trailer coupling mechanism.

Any thoughts?

[ROBERT CROSS]

...Not really, they only use surge brakes on their larger trailers and don't care that your headlights are stargazing.

Bob
🇺🇸

[wulfraat]

I those trailers (at least the ones I've rented) typically deploy surge braking mechanisms, which are not (generally speaking) compatible with WD and anti-sway hitches as they can restrict the movement of the braking mechanism.

They typically also have low GVWR, which reduces risk further from sway / heavy tongue that requires WD.

My wife drove our 2500 from Denver to Las Vegas tugging a U-haul trailer which probably weighed about 1,500lbs loaded. I had no concerns whatsoever for her safety.

That is my guess anyways... there are lots of knowledgeable folks on the forum who I'm sure weigh in.

[Profxd]

Those over at UHaul are pretty smart people.
https://www.trailer-bodybuilders.com...ailer-dynamics

[pteck]

What wulfraat said about surge brakes being incompatible with WD equipment.

That said, U-Haul equipment is exceeding robust for the expected abuse they go though. They won't let you tow if the tow vehicle to trailer combination is not safe based on their database.

They also have some design elements that help protect from sway. Namely longer draw bars. This helps to minimize actual tongue weight on the vehicle, yet ensures that the center of gravity (what it's really about) that we like to reference as having enough tongue weight, is sufficiently ahead of the trailer axle to ensure stability and sway resistance.

[ROBERT CROSS]

Yep...they sure are smart. 🤓
A toy car on a treadmill.😂

Bob
🇺🇸

[Profxd]

They have to dumb it down so people on forums can understand it
Jim Fait is also chairman of the SAE Trailer Committee, he understands towing dynamics better than anyone on this forum for sure.

[OTRA15]

Let the sway games begin!

A parallel universe: http://www.airforums.com/forums/f382...er-193285.html

[ROBERT CROSS]

Originally Posted by Profxd

They have to dumb it down so people on forums can understand it
Jim Fait is also chairman of the SAE Trailer Committee, he understands towing dynamics better than anyone on this forum for sure.

We be dumb all right...but happy.😁

I have never seen an AS designed like the trailer on the treadmill, single axle located dead center, and it sways...da.
I'm sorry but I feel that was just a cover your butt demonstration.

Setting up an AS properly is not SAE difficult. 🤓
Common sense, CAT tickets and/or a tape measure, all us dumb people can do it.👍

Bob
🇺🇸

[jcanavera]

Watched a single axle U Hall box trailer in a nose down position go into a yaw while being pulled by a Chevy Monte Carlo. I was behind him on the highway and we were both doing about 60. I noticed the sway and dropped back behind him. As the arc of the sway increased I knew he was going to lose control. I saw him throw on the brakes and the trailer back end of the car lost traction and the car skidded perpendicular to the highway. The trailer at that point was at a 45 degree angle fro the car. They all stayed upright and skidded off the shoulder. Very scary. I remember those trailers used to have decals that said max speed 45 mph on them.

Jack

[pteck]

Boy are we a dysfunctional group. Toys are so beneath them as to provide no value?

For the uninformed, this is called a model based design. It is as legit as diagrams on a paper for which some might call a "drawing". Every discipline that has ever done design or engineering work, or heck just laying out a yard, utilizes drawings and if warranted, models to help understand and iterate.

It helps set the context, describe, and visualize the problem. In this case, to help layman better understand the dynamics of what's happening when putting too much load behind the rear axle. The proportions may be different, and it doesn't look like a 3/4 ton truck and AS, but the fundamental dynamics are absolutely the same.

For those interested in more than just "load behind rear axle". It's really about the center of gravity. When the center of gravity of the trailer is ahead of the rear axle, it is stable. Once the center of gravity moves rear, and ultimately past the rear axle, it get unstable to the degree that the center of mass goes further to the rear.

WD, PPP, HD trucks will help control and dampen the motions. But ultimately, get the tongue weight and center of gravity wrong, and with enough speed and force at play, it will bite you.

[ROBERT CROSS]

Jack,

It's now 55mph to avoid... "Combination Disturbances" 🤔


"REDUCE SPEED to 55 mph or LESS.
Combination disturbances happen most often at higher speeds."

Toys do provide value...as playthings, like Airstreams.

Bob
🇺🇸

[out of sight]

U-Haul has to make their trailers idiot proof so that weekend warriors who have never towed before can tow them without wrecking them. They seem to have settled on two basic conditions for safe towing, namely, loading the trailer with at least 60% of the load in front of the trailer axle, and having a tow vehicle with a curb weight of at least 80% of the trailer gross weight. They also tell you not to go over 55 mph even though they know most people won't adhere to that but hopefully will not exceed highway speed limits.

[rmkrum]

Probably have the speed limit in their contract and on warning placards on their equipment to limit their liability. If you tow a Uhaul faster than what it’s marked for, liability will land on you, if push comes to shove, for violating the agreed speed limit. I can’t blame them. I’ve seen folks towing Uhaul hardware doing way over the speed limit. And in California, any vehicle towing a trailer is limited by law to no more than 55 miles per hour. Most of them are not even close to going the posted speed limit, trailer or not.
I usually set cruise control to no more than two or three MPH over, and I constantly get passed like I’m parked...and it’s particularly disturbing when it’s a dinky pickup pulling a 30 foot SOB toy hauler trailer with three feet of air under it. Their headlights are usually lighting up the trees as well.
I just let them go by, and hope I can stop before I get to their debris field down the road...

And we won’t talk about how they drive in the rain and fog. Lately it’s been rather wet and windy out here.

[gypsydad]

Originally Posted by ROBERT CROSS

Jack,

It's now 55mph to avoid... "Combination Disturbances" ��


"REDUCE SPEED to 55 mph or LESS.
Combination disturbances happen most often at higher speeds."

Toys do provide value...as playthings, like Airstreams.

Bob
����

Love that shirt!

[RedSHED]

Originally Posted by ROBERT CROSS

Jack,

It's now 55mph to avoid... "Combination Disturbances" [emoji848]


"REDUCE SPEED to 55 mph or LESS.
Combination disturbances happen most often at higher speeds."

Toys do provide value...as playthings, like Airstreams.

Bob
[emoji631]

I'll bite. What parts of the displayed physics become invalid when scaled up?

The Wright brothers used a wind tunnel; rocket scientists still do. Are they doing it wrong?

[ROBERT CROSS]

...bite?

Are you saying we should not consider our Airstreams toys?

Bob
🇺🇸

[Mattirs]

Originally Posted by ROBERT CROSS

...bite?

Are you saying we should not consider our Airstreams toys?

Bob
[emoji631]

Wish I could afford to call it a toy [emoji56]

[Profxd]

Originally Posted by pteck

Boy are we a dysfunctional group. Toys are so beneath them as to provide no value?

For the uninformed, this is called a model based design. It is as legit as diagrams on a paper for which some might call a "drawing". Every discipline that has ever done design or engineering work, or heck just laying out a yard, utilizes drawings and if warranted, models to help understand and iterate.

It helps set the context, describe, and visualize the problem. In this case, to help layman better understand the dynamics of what's happening when putting too much load behind the rear axle. The proportions may be different, and it doesn't look like a 3/4 ton truck and AS, but the fundamental dynamics are absolutely the same.

For those interested in more than just "load behind rear axle". It's really about the center of gravity. When the center of gravity of the trailer is ahead of the rear axle, it is stable. Once the center of gravity moves rear, and ultimately past the rear axle, it get unstable to the degree that the center of mass goes further to the rear.

WD, PPP, HD trucks will help control and dampen the motions. But ultimately, get the tongue weight and center of gravity wrong, and with enough speed and force at play, it will bite you.

Just as important as the COG is the position of the trailer axles. The further rearward the trailer axles are on the frame, the better the stability. This increases the distance of the coupler to the COG. So you can have a trailer that handles poorly even with the COG positioned just ahead of the trailer axles centerline.

[pteck]

Originally Posted by Profxd

Just as important as the COG is the position of the trailer axles. The further rearward the trailer axles are on the frame, the better the stability. This increases the distance of the coupler to the COG. So you can have a trailer that handles poorly even with the COG positioned just ahead of the trailer axles centerline.

Important. But we don't have much control to locate the axles. [emoji3]