Which load leveling hitch?

[SailorSam205]

In his argument, Out of Sight has one small portion of the issue right: removing weight from your tow vehicle's rear axle will make your rig less stable. That is having less load than before WD is applied.

What he seems unable to accept is that a WD does not move enough weight from the rear axle to make it lower than before the trailer is hooked up. I have yet to see any weigh results where the rear axle load was lower than before the trailer was added. My observation is that, in fact, all axles have more weight on them than before the trailer is hitched to the TV.
At the opposite extreme, I recently spotted a 3/4 ton pulling a large landscape trailer. As it went over the crown at an intersection, the front wheels bounced!

[SteveSueMac]

SailorSam - spot on. Even CAT tickets don’t seem to convince.

I’ve shared mine many times from many weights - beginning of this season the following 3 numbers are my truck’s drive axle weights solo, with trailer no WD then with trailer and WD applied:

3340
4840
4480

Far from lightening the rear axle, even with WD applied - I’m adding 1140# to the rear axle of the truck.

I also lift almost 500# off the drive/front axle of the truck (a 3/4T diesel - a beast of a truck by any stretch) and return about 2/3 of that by applying WD. Absent that - I experience porpoising and a different feeling in the steering capability of the truck.

I don’t know why the anti-WD argument continues to get thrown out there - it should just be thrown out period.

[Profxd]

His principle is indeed correct to a point but most vehicles will tolerate at least a little WD. It has everything to do with how the added tongue weight effects TV handling (understeer/oversteer). Adding tongue weight to the TV reduces understeer, adding any amount of WD will lower even further. For every specific TV/trailer combination there is a optimal TW that maintains a positive understeer condition on the TV, yet still has enough TW to keep the sway critical speed above normal highways speeds. It’s a trade off or a balance between the two instability modes that should be targeted since what improves one makes the other worse.

[SteveSueMac]

Originally Posted by Profxd

Adding tongue weight to the TV reduces understeer, adding any amount of WD will lower even further.

What? Man - the dynamic duo rides again...

First - putting tongue weight on the rear of the TV can INDUCE the understeer condition by acting like a lever and lifting weight off the front end of the TV. Lightening the steer axle contributes to - doesn’t reduce - an understeer condition. See definition attached.

Then you argue that applying WD (which would restore weight lifted off the TV’s front axle) further exacerbates a condition it doesn’t create in the first place!

That is some form of magic!

It’s like saying - putting sugar in coffee makes it bitter. Adding cream only makes it even more bitter.

Show me scale tickets that suggest otherwise and it will be fun to continue the discussion. Otherwise - I’d apply the same warning to your posts as to his - caveat emptor.

[Profxd]

Originally Posted by SteveSueMac

What? Man - the dynamic duo rides again...

First - putting tongue weight on the rear of the TV can INDUCE the understeer condition by acting like a lever and lifting weight off the front end of the TV. Lightening the steer axle contributes to - doesn’t reduce - an understeer condition. See definition attached.

Then you argue that applying WD (which would restore weight lifted off the TV’s front axle) further exacerbates a condition it doesn’t create in the first place!

That is some form of magic!

It’s like saying - putting sugar in coffee makes it bitter. Adding cream only makes it even more bitter.

Show me scale tickets that suggest otherwise and it will be fun to continue the discussion. Otherwise - I’d apply the same warning to your posts as to his - caveat emptor.

Attachment 356510

The addition of mass to the TV behind the rear axle is what will reduce the desired understeer. The problem with the WDH is that it doesn’t move or relocate any mass. Reducing normal load on the rear tires reduces the cornering stiffness (they’re ability to resist lateral force) while the force acting on them from the mass stays the same. It is best to minimize TW and the use of a WDH as much as possible.

[SteveSueMac]

Originally Posted by Profxd

It is best to minimize TW and the use of a WDH as much as possible.

AS instructions require 10-15% TW - do you disagree with them?

They also recommend using scales to weigh axles.

When 10-15% TW connects to my 3/4T diesel, nearly 500# lifts off the drive axle. WD addresses that issue while leveling the load across the 3 sets of axles that make one continuous rig.

[Bobbo]

Originally Posted by Profxd

The addition of mass to the TV behind the rear axle is what will reduce the desired understeer. The problem with the WDH is that it doesn’t move or relocate any mass. Reducing normal load on the rear tires reduces the cornering stiffness (they’re ability to resist lateral force) while the force acting on them from the mass stays the same. It is best to minimize TW and the use of a WDH as much as possible.

Ummm, not quite. The addition of weight (mass times the force of gravity) to the TV behind the rear axle INDUCES understeer by removing pressure from the front axle. (Note how the front fender rises.) The WDH moves a portion of that pressure back to the front axle, thereby reducing understeer.

That is why the weights when measured at CAT scales change under these conditions. It is due to the varying downward pressures on the axles.

[out of sight]

Part of the marketing myth is that removing load from the front axle is dangerous. This may be true in the extreme, but today's vehicles are designed so that it is virtually impossible to dangerously underload the front axle without overloading the rear axle, and if you're overloading the rear axle then what you need is a bigger tow vehicle, not a wd hitch.

You should not experience any steering issues even with a 60/40 rear/front weight distribution (indeed formula one cars steer nicely with 65/35). My rig is 52/48 towing on the ball, and it steers perfectly and handles solid as a rock.

[Bobbo]

Originally Posted by out of sight

Part of the marketing myth is that removing load from the front axle is dangerous. This may be true in the extreme, but today's vehicles are designed so that it is virtually impossible to dangerously underload the front axle without overloading the rear axle

Again, wrong. Removing sufficient load from the front axle IS dangerous. It doesn't take extreme loading to do so. No vehicle is, or can possibly be, designed to make it "virtually impossible to dangerously underload the front axle without overloading the rear axle." Put enough weight far enough behind the rear axle and you will get significant front axle underload while adding significantly less rear axle load. Look at a child's teeter totter for an example. You underload the left side enough to raise that child into the air while, at the same time, placing only a small portion of that weight onto the pivot point (which is the TV rear axle in our case). Levers have been known for millennia.

[JonDNC]

Originally Posted by out of sight

You should not experience any steering issues even with a 60/40 rear/front weight distribution (indeed formula one cars steer nicely with 65/35). My rig is 52/48 towing on the ball, and it steers perfectly and handles solid as a rock.

This is a gross simplification- F1 cars might have that weight bias but have tons (literally) of downforce at speed. I track a newer 911 of which is known to have some under steer and significant rear weight bias. That’s why you corner differently in a 911 then a Cayman (50/50) weight distribution. Taking too much weight off the front is dangerous.

I am a believer in WD even on my F350. The key is work the numbers to correct just enough

[out of sight]

So how much weight off the front axle is dangerous as far as steering and handling go? 50/50 is an ideal rear/front weight distribution that some people tout. I can vouch for 52/48 as working very well. Certainly you can't find any technical rationale anywhere for having more load on the front than on the rear.

Realizing that this is an issue that nobody will ever agree on, what's your idea rear/front weight distribution?

[JonDNC]

Originally Posted by out of sight

So how much weight off the front axle is dangerous as far as steering and handling go? 50/50 is an ideal rear/front weight distribution that some people tout. I can vouch for 52/48 as working very well. Certainly you can't find any technical rationale anywhere for having more load on the front than on the rear.



Realizing that this is an issue that nobody will ever agree on, what's your idea rear/front weight distribution?

Darned if I know, not an automotive engineer. But according to most experts 50/50 is the magic number.

I do know that under hard acceleration I can feel the front wheels get lighter on the 911, which is why it’s important when driving at those speeds to properly apply throttle.

For our discussion on towing my thought is follow the manufacturer recommendations on how much weight to return and what are the max load limits per axle. They’ve done the math.

[Profxd]

I do not disagree with the 10-15% TW requirement. But if you can reduce TW from 14% to say 12%, still maintain sway stability at highway speeds, and use less WD the rig will handle much better.

[Profxd]

Originally Posted by JonDNC

Darned if I know, not an automotive engineer. But according to most experts 50/50 is the magic number.

I do know that under hard acceleration I can feel the front wheels get lighter on the 911, which is why it’s important when driving at those speeds to properly apply throttle.

For our discussion on towing my thought is follow the manufacturer recommendations on how much weight to return and what are the max load limits per axle. They’ve done the math.

There’s more to understeer/oversteer then just weight distribution alone. Most class 2b trucks and higher use a tire pressure differential front to rear and it’s purpose is to maintain understeer with significantly higher loading on the rear axle. Suspension design can also control and maintain understeer under load conditions.

[out of sight]

Correct. My RAM 2500 calls for 80 PSI rear and 65 PSI front for this reason, which I maintain carefully.

I have noticed from other posts that people are adjusting their tire pressures on their trailers and tow vehicles based on trying to get a more comfortable ride. They go to the tire manufacturer's load chart to determine what's best. But I think it's important to follow the vehicle manufacturer's recommendations because they are more concerned about handling when they set their pressures.

[JonDNC]

Originally Posted by Profxd

There’s more to understeer/oversteer then just weight distribution alone. Most class 2b trucks and higher use a tire pressure differential front to rear and it’s purpose is to maintain understeer with significantly higher loading on the rear axle. Suspension design can also control and maintain understeer under load conditions.

Ok tried to keep it simple. Yes there’s way more to understeer/oversteer. This is probably not the forum.

Tire pressure/ alignment/ spring stiffness / sway bars, weight transfer, corner balance, etc. all impact under/over steer. The discussion is never ending and covered in depth on most racing boards etc.

[out of sight]

And now truck manafacturers are stuck having to pass the SAE J2807 understeer test.

[JonDNC]

Originally Posted by out of sight

Correct. My RAM 2500 calls for 80 PSI rear and 65 PSI front for this reason, which I maintain carefully.



I have noticed from other posts that people are adjusting their tire pressures on their trailers and tow vehicles based on trying to get a more comfortable ride. They go to the tire manufacturer's load chart to determine what's best. But I think it's important to follow the vehicle manufacturer's recommendations because they are more concerned about handling when they set their pressures.

In my experience the door sticker is based on max load, if you’re not running max load then all the other factors come into play. FWIW on my F350 which calls for 60F/80R on the sticker, I set the rears at 75 when towing as way under max load according to the CAT scales and 70 no load. All cold pressures. Works great and wear is even on the tires.

[out of sight]

Since I don't use a wd hitch my drive axle is fairly well loaded at 79% GAWR. There may be a better combination than 80/65 PSI but since I am very pleased with both the towing stability and the smoothness of the ride I figure I'll leave well enough alone. Probably you're right though that the recommended pressures are to accommodate the maximum towing condition.

[Dan and Liz]

Originally Posted by out of sight

So how much weight off the front axle is dangerous as far as steering and handling go? 50/50 is an ideal rear/front weight distribution that some people tout. I can vouch for 52/48 as working very well. Certainly you can't find any technical rationale anywhere for having more load on the front than on the rear.

Realizing that this is an issue that nobody will ever agree on, what's your idea rear/front weight distribution?

I haven’t seen anything on this forum suggesting it’s wise to have more load on the front (steer) axle than on the rear while towing. Why would any technical rationale be needed for something no one has promoted?