WD Hitch Set Up question

Ron Gratz wrote:

yukonpete wrote:
---What gets me is the user guide syas it should be within 1/2".

Curt's recommendation that

Vehicle should settle evenly, within 1/2"

is a holdover from 50 years ago when the most common tow vehicle was the family sedan.
Curt's recommendation is the so-called "equal squat" approach which has been abandoned by most WDH and TV manufacturers.

I think the reason Ford, Chevrolet, Toyota, Equal-i-zer, Reese and others have changed their weight distribution specifications is pretty well summed up in this Letter to Editor by Richard H Klein, P E printed in TRAILER BODY BUILDERS Magazine. The comment which specifically addresses front axle load is:

QUOTE
2. The statement “too much tongue weight can force the truck down in the back, causing the front wheels to lift to the point where steering response and braking can be severely decreased” is not the real issue with heavy tongue weights. The real problem is that the tow vehicle's yaw stability, as measured by “understeer gradient”, is severely decreased. This increases the propensity of the tow vehicle to jackknife in turning maneuvers. Specifically, recent full scale testing conducted by the SAE Tow Vehicle Trailer Rating Committee (and now published in SAE J2807), determined that the use of weight distributing hitch torque should be minimized. In fact they recommend that the Front Axle Load Restoration (FALR) not exceed 100% (100% means that the front axle weight is brought back, via weight distribution, to a weight equal to its “no trailer” condition).
UNQUOTE

A related explanation from a representative of the company which manufactures the Equal-i-zer hitch was first posted here. It says:

QUOTE

In the past we had suggested that you should see a small drop on the front suspension. We are always trying to improve things here at Progress – our motto is “Safe and Happy Customers,” and so we are always reviewing our instructions and installation process. Recently, as part of this constant effort our engineers looked more deeply into this aspect of installation. We had always felt that a small drop was a sign that the trailer’s weight was being transferred to the front axle, and that this was essentially a good thing.

As our engineers reviewed the instructions for the last round of renewal of our instructions, the found research results that contradicted our prior thinking. There has been a substantial amount of testing conducted by experts from SAE and the RV Industry Association to find out what will produce the best stability when towing. This towing suggests that you want your front axle’s compression to be close to, but not lower than your free-standing height.

(Underline added for emphasis.)
UNQUOTE

Ford says the Front Axle Load Restoration should be approximately 50%.

Chevrolet/GMC says the FALR should be 100%, 50% or 0% depending on TV model and TT weight.

Equal-i-zer says the Front Axle Load Restoration should be between 50% and 100%.

Equal-i-zer's revised instructions specifically state:

Good adjustment:
You have most likely achieved good weight distribution adjustment if your measurements show the following with the trailer coupled and the weight distribution engaged:
1. From the coupled without weight distribution measurement, the front wheel well measurement is at least halfway back to the original uncoupled measurement. See line C on Front Wheel Well Measure Chart.
2. The rear wheel well measurement is somewhere between the uncoupled height, and the coupled with no weight distribution height. It should NEVER be higher than the uncoupled height. See line C on Rear Wheel Well Measure Chart. See Figure 19.

It's up to the owner of a WDH and TV to decide whether to follow the outdated recommendation of a WDH manufacturer or the up-to-date recommendation of a TV manufacturer.
I would choose the latter.

Ron

I would also choose the latter. Number 2 implies that the measurement of the rear fender height should be addressed. That in itself is enough to make the inexperienced or first timer think that the hitch should be tweaked to level the truck, and we know that is not true.

Another item to note: The measurements are decent references to get the truck 'in the ballpark'. The truly dial it in, WEIGH THE RIG!! It's easy, costs $11 or $12 at most, and gives you the opportunity to see exactly how effective (or INeffective) your setup is at managing the tongue weight.

yukonpete wrote:
---What gets me is the user guide syas it should be within 1/2".

Curt's recommendation that

Vehicle should settle evenly, within 1/2"

is a holdover from 50 years ago when the most common tow vehicle was the family sedan.
Curt's recommendation is the so-called "equal squat" approach which has been abandoned by most WDH and TV manufacturers.

I think the reason Ford, Chevrolet, Toyota, Equal-i-zer, Reese and others have changed their weight distribution specifications is pretty well summed up in this Letter to Editor by Richard H Klein, P E printed in TRAILER BODY BUILDERS Magazine. The comment which specifically addresses front axle load is:

QUOTE
2. The statement “too much tongue weight can force the truck down in the back, causing the front wheels to lift to the point where steering response and braking can be severely decreased” is not the real issue with heavy tongue weights. The real problem is that the tow vehicle's yaw stability, as measured by “understeer gradient”, is severely decreased. This increases the propensity of the tow vehicle to jackknife in turning maneuvers. Specifically, recent full scale testing conducted by the SAE Tow Vehicle Trailer Rating Committee (and now published in SAE J2807), determined that the use of weight distributing hitch torque should be minimized. In fact they recommend that the Front Axle Load Restoration (FALR) not exceed 100% (100% means that the front axle weight is brought back, via weight distribution, to a weight equal to its “no trailer” condition).
UNQUOTE

A related explanation from a representative of the company which manufactures the Equal-i-zer hitch was first posted here. It says:

QUOTE

In the past we had suggested that you should see a small drop on the front suspension. We are always trying to improve things here at Progress – our motto is “Safe and Happy Customers,” and so we are always reviewing our instructions and installation process. Recently, as part of this constant effort our engineers looked more deeply into this aspect of installation. We had always felt that a small drop was a sign that the trailer’s weight was being transferred to the front axle, and that this was essentially a good thing.

As our engineers reviewed the instructions for the last round of renewal of our instructions, the found research results that contradicted our prior thinking. There has been a substantial amount of testing conducted by experts from SAE and the RV Industry Association to find out what will produce the best stability when towing. This towing suggests that you want your front axle’s compression to be close to, but not lower than your free-standing height.

(Underline added for emphasis.)
UNQUOTE

Ford says the Front Axle Load Restoration should be approximately 50%.

Chevrolet/GMC says the FALR should be 100%, 50% or 0% depending on TV model and TT weight.

Equal-i-zer says the Front Axle Load Restoration should be between 50% and 100%.

Equal-i-zer's revised instructions specifically state:

Good adjustment:
You have most likely achieved good weight distribution adjustment if your measurements show the following with the trailer coupled and the weight distribution engaged:
1. From the coupled without weight distribution measurement, the front wheel well measurement is at least halfway back to the original uncoupled measurement. See line C on Front Wheel Well Measure Chart.
2. The rear wheel well measurement is somewhere between the uncoupled height, and the coupled with no weight distribution height. It should NEVER be higher than the uncoupled height. See line C on Rear Wheel Well Measure Chart. See Figure 19.

It's up to the owner of a WDH and TV to decide whether to follow the outdated recommendation of a WDH manufacturer or the up-to-date recommendation of a TV manufacturer.
I would choose the latter.

Ron

Thanks for all the help guys. The front drops 1/4" and the rear 1 1/4" when set up on the WDH so I think it should be good. I did take her on a 30 mile test run without any issues! What gets me is the user guide syas it should be within 1/2".

It is not uncommon for the rear to drop 1.5-2" when using a properly-adjusted WDH.
A drop of 1.25" is not a large amount.

As others have stated -- if you get the front height correct for your TV, the rear end will take care of itself.

If you check your owners manual, I believe it will say that the WDH should be adjusted to eliminate about 50% of the front-end rise.
IOW, if the tongue weight without WD applied causes the front to rise 1", you should adjust the WDH to lower the front end rise to about 0.5"

You definitely should not try to force the front end below the unhitched height.
The WDH manufacturers who recommend doing so are following an outdated WDH-adjustment approach.

Ron

Measure the height of the front and the rear at a convenient point on the fender wells. record these dimensions. When the hitch is set, and the trailer on the hitch, W/D hars up, you want the truck to settle approximately the same on the front and the rear fenders measurements.

ken

How far the rear drops is directly affected by tongue weight. If you have the front correct don't sweat the rear. Refer to the truck owners manual for correct procedure. All makes are not the same.

yukonpete wrote:
I am setting up my CURT Long Trunnion Bar Weight Distribution Hitch #17302 and the user manual says the rear and front bumper should settle within 1/2" of the unhitched position when setup correctly! My problem is I can't reach this number on my rear axle after many hours of trying. My front axle settles about 1/4" and the rear axle 1 1/14".

I have a 2012 F150 Supercab V8. Trailer weight is 6000 Lbs

While 1 1/2" is a lot for the rear to drop. IF you have the front back down. You are replacing the lost weight. You should be good. Take a test tow, and see how well it follows.

The only real way to know you have it right is to weigh both axles before and after. Usually only necessary when doing it the first time since after that you know where to set the bars each time you hook things up.

Also:

I followed your other thread on this topic and thought you had a W/D hitch with integrated sway control, but I see now that I was wrong. For my own information, may I ask what type/brand of add-on sway controller you're using?

There's no spec for the rear because the purpose of WD is not to level the truck. Get the from where it needs to be according to the owners manual and leave the rest alone.