How much of rise on front of truck acceptable when hitched?

JRscooby wrote:
Can you explain how the "squat without taking weight off"?
Look at a lever on fulcrum. Add weight to 1 end, weight comes off the other end. The fact the fulcrum moves (rear suspension compression) does not change that.

With simple ball hitch, yes, the frame will act as a simply supported beam and yes, it will take some weight off the front axle if you put any weight on the hitch. Of course, with the really long wheelbase trucks (4 door long bed), it takes negligible weight off the front axle while all the hitch weight, all the in bed cargo weight and any weight off the front axle...goes onto the rear axle. So if you take 150lb off the front axle, you might be adding 1500lb to the rear axle when you are fully loaded. The result is...it will be hard to accurately measure any rise in the front axle while the rear axle is likely doing to drop by at least a couple inches (depends on the truck model...1/2 tons will be more duallys less)

But with a WDH, the trucks frame no longer acts as a simply supported beam, so you can't consider it a simply supported beam.

Grit dog wrote:



RVing is not totally unique but it’s sort of unique in that most people consider it a right to go RVing when there are no requirements or training necessary to operate something that would otherwise require training or certification in the commercial world. Thus there is an abnormally large % of consumers who are blissfully ignorant about some or many aspects of operating or controlling a heavy vehicle or combo.
When one observes the relatively large % of people who are challenged by simply operating the smallest of passenger vehicles combined with the fact that all it takes is a credit card, cash or a line of credit to instantly be the operator of a heavy vehicle. And not the typical commercial application where there is a greater chance of skill, training or experience or knowledge being gained or passed down then you get information published like this to help people save themselves from themselves.

Reading this statement by somebody that generally knows what he is talking about should scare rational people.

Three Pass Scale Method (Ron Gratz, back in 2010)
All passengers aboard every time. Full fresh water & propane. Both vehicles loaded for a camping trip.

1). First weigh with hitch tensioned.

2). Second weigh with bars fully slack

3) Third weigh is TV only.

I have never understood what useful information is gained with the second pass. TW, the only number for TW that affects handling is TW when ready to hit the road. Can get that by adding S + D together, subtracting gross from third pass. Know if rear axle is overweight before bars are hooked up? Normal hookup, do you get tongue jack off ground before hooking up bars?

valhalla360 wrote:

Also, need to differentiate front rise from change in frame angle. When empty, pickups typically sit a bit high in the back, so squatting a bit without taking any weight off the front axle can make it appear the front is lifting if just doing a visual check.

Can you explain how the "squat without taking weight off"?
Look at a lever on fulcrum. Add weight to 1 end, weight comes off the other end. The fact the fulcrum moves (rear suspension compression) does not change that.

Grit dog wrote:
First, if you can transfer more weight to the front than it originally had, time to re think your need for a wdh or you’re doing it wrong.

It's certainly possible to put more weight back on the front axle than it originally had. There was a marketing campaign back in the 60-70's where they went silly with the WDH (front wheel drive vehicle). They would then drive it around without the rear tires.

In principal, keeping the front/rear axle weight distribution the same would be ideal but in practice it's rarely practical. Setting a limit recommendation avoids 99% of the times when it could cause problems.

Also, need to differentiate front rise from change in frame angle. When empty, pickups typically sit a bit high in the back, so squatting a bit without taking any weight off the front axle can make it appear the front is lifting if just doing a visual check.

https://www.rvlifemag.com/taking-the-mystery-out-of-torsion-bars/

https://www.rvlifemag.com/understanding-ball-mount-angle/

https://www.rvlifemag.com/how-to-set-up-a-weight-distributing-hitch-system/


Bars well-chosen and then set at home, take to a CAT SCALE (phone app available) and get the real numbers. There’s an adjustment range from heavy to light with your combined rig. The scale helps you dial it in today, and to diagnose problems in the future.


Three Pass Scale Method (Ron Gratz, back in 2010)
All passengers aboard every time. Full fresh water & propane. Both vehicles loaded for a camping trip.

1). First weigh with hitch tensioned.

2). Second weigh with bars fully slack

3) Third weigh is TV only.

STEER AXLE in #1 & #3 the same (you’re done).
Make adjustments to get close as can be without going over.

A 5’er/GN loads the Steer Axle the same way: no change.

Handling is different of course. But we want steering & braking to be close to the loaded/solo value.

You think you have it close, then test brake control adjustment. SHOULD STOP FASTER FROM 30MPH WHEN HITCHED.

A). Tire pressure take from #1 (or corrected) as against Load & Pressure Table (but not lower than TV manufacturers range). Too much air is BAD idea, worsens braking & steering.

B). Note FF/RR weight bias of TV in #3. Closest to 50/50 before hitching means better outcome. Too much forward = you bought the wrong TV (high rear spring rate not your friend unless utilized in main).

— A 1,000-lb TW is the province of cars. Pickup not needed. The 1/3-Distribution goal means “maybe” 500-lbs static on ball at rest. 10-15% TW which #2 tells you.

The numbers tossed around are placeholders. Towing involves road-going dynamics where the force on the ball can go sky-high, or go super low. The WDH applies these forces across the entirety of the combination vehicle.

Done right, it tracks on rails. Stay with it until this is the outcome. (Anti-sway is a separate subject, but it’ll still need the above).

Andy & his father codified what the rest of us learned more than fifty years ago. That dealership has set up more than 14,000 tow rigs. He’s a consultant on towing to both Airstream and SAE.

.

Steering should feel the same with or without the trailer.

ktmrfs wrote:
seems like every mfg had different advice on how much to bring the front down and they seem to vary year to year.

I've always tried to bring mine back to 1/2" or less but NEVER NEVER EVER below the original ride height. Especially important on GM since you can easily run into the rubber bump stops if you go below unloaded height.

My opinion is if your at 1/2" see how it handles your likely in the ballpark acceptable range.

First, if you can transfer more weight to the front than it originally had, time to re think your need for a wdh or you’re doing it wrong.
Second, there’s a reason mfgs recommendations (note, not “requirements”) change frequently. 1. It’s only a blanket general recommendation. 2. You can lose significant weight off the FA of some vehicles and not affect steering and braking from a real world standpoint.
3. A good portion of the recommendation is just liability, corporate cya, like the volumes of other hazard warnings that have been developed to save people from un-knowingly doing really stupid things and claiming ignorance and willful carelessness by those with deep pockets, in front of the judge.

RVing is not totally unique but it’s sort of unique in that most people consider it a right to go RVing when there are no requirements or training necessary to operate something that would otherwise require training or certification in the commercial world. Thus there is an abnormally large % of consumers who are blissfully ignorant about some or many aspects of operating or controlling a heavy vehicle or combo.
When one observes the relatively large % of people who are challenged by simply operating the smallest of passenger vehicles combined with the fact that all it takes is a credit card, cash or a line of credit to instantly be the operator of a heavy vehicle. And not the typical commercial application where there is a greater chance of skill, training or experience or knowledge being gained or passed down then you get information published like this to help people save themselves from themselves. (Good info for sure, but evidenced by how many weekend warriors and “pro” RVers alike have very little to no knowledge formal or otherwise and are not even able to correctly interpret these recommendations and their relative value, these recommendations become a very conservative, necessary approach to limiting corporate liability.)

Equalizer WD hitches list on their setup instructions for a 50% to 100% return. But they also recommend following the TV ratings

Mike

seems like every mfg had different advice on how much to bring the front down and they seem to vary year to year.

I've always tried to bring mine back to 1/2" or less but NEVER NEVER EVER below the original ride height. Especially important on GM since you can easily run into the rubber bump stops if you go below unloaded height.

My opinion is if your at 1/2" see how it handles your likely in the ballpark acceptable range.

Ford wants you to return 50% of the hitched distance and no more.
If it rises 1" without WDH hooked up then yes you're fine. If it rises 1.5" then you're reducing it too much.

^What he said.
All depends on how it handles.