Is our Audi Q5 able to tow a 19 foot Bambi?

[DKB_SATX]

Originally Posted by Andy543

Please post the SAE version on line. You won't get sued, because it's a publicly financed paper, paid for by the taxpayers. In fact, the SAE, and maybe the authors, could be sued here.

Present your test results to support your statements. Otherwise, admit your misinterpretation.

A HUGE problem with discussion of this report is in understanding what he's measured and translating that to the way we talk about weight distribution today. Vehicle manufacturers focus on Front Axle Load Restoration (FALR), measured as a percentage of the difference between the no-trailer front axle force and the trailer-but-no-weight-distro front axle force. Klein, in his paper from the 70s, is measuring the percentage of the tongue-weight transferred to the front axle. What Klein calls "50% load-leveling force" results in 111% FALR (p. 56 paragraph 3) which is VASTLY more than most manufacturers recommend, even more than the surprising 100% that Toyota recommends for the Tundra. It results in only 80 lb of a 600-lb tongue weight being carried by the rear axle of the test tow vehicle, which is an absurd condition.

So, I stand by my statement that a properly-configure WD hitch is not some "oversteer risk" but any tool can be misused. Intentionally or not, jcl is not the one misrepresenting the results reported in this paper.

[Andy543]

Originally Posted by DKB_SATX

A HUGE problem with discussion of this report is in understanding what he's measured and translating that to the way we talk about weight distribution today. Vehicle manufacturers focus on Front Axle Load Restoration (FALR), measured as a percentage of the difference between the no-trailer front axle force and the trailer-but-no-weight-distro front axle force. Klein, in his paper from the 70s, is measuring the percentage of the tongue-weight transferred to the front axle. What Klein calls "50% load-leveling force" results in 111% FALR (p. 56 paragraph 3) which is VASTLY more than most manufacturers recommend, even more than the surprising 100% that Toyota recommends for the Tundra. It results in only 80 lb of a 600-lb tongue weight being carried by the rear axle of the test tow vehicle, which is an absurd condition.

So, I stand by my statement that a properly-configure WD hitch is not some "oversteer risk" but any tool can be misused. Intentionally or not, jcl is not the one misrepresenting the results reported in this paper.

I agree with you that Toyota's recommendation seems bizarre. They should read Klein's paper. But the paper, and the test results, are crystal clear: weight distribution, i.e., taking load off the rear axle with a spring mechanism, increases the risk of oversteer, and subsequently a jackknife accident.

[DKB_SATX]

Originally Posted by Andy543

I agree with you that Toyota's recommendation seems bizarre. They should read Klein's paper. But the paper, and the test results, are crystal clear: weight distribution, i.e., taking load off the rear axle with a spring mechanism, increases the risk of oversteer, and subsequently a jackknife accident.

FUD. The clear statement is that taking TOO MUCH load off the rear axle (vastly more than recommended by modern manufacturers) is indeed problematic, but taking reasonable amounts (in the range of 50% FALR) achieves both load-leveling and reduced understeer, improved braking for trailers with electric brakes towed by vehicles with a front braking bias (essentially all modern vehicles.) Also clearly expressed is that taking all the tongue weight off the rear axle (which no one recommends doing) is too much and yields negative results. And in his first recommendation (p. 70, E. 1.) he left-handedly recommends the re-examination of slimp dollies (!)

[Andy543]

Originally Posted by DKB_SATX

FUD. The clear statement is that taking TOO MUCH load off the rear axle (vastly more than recommended by modern manufacturers) is indeed problematic, but taking reasonable amounts (in the range of 50% FALR) achieves both load-leveling and reduced understeer, improved braking for trailers with electric brakes towed by vehicles with a front braking bias (essentially all modern vehicles.) Also clearly expressed is that taking all the tongue weight off the rear axle (which no one recommends doing) is too much and yields negative results. And in his first recommendation (p. 70, E. 1.) he left-handedly recommends the re-examination of slimp dollies (!)

Fear Uncertsinity Doubt. That's what sells hitches, isn't it? I would suggest instead that you go with science.

[jcl]

Originally Posted by Andy543

Please post the SAE version on line. You won't get sued, because it's a publicly financed paper, paid for by the taxpayers. In fact, the SAE, and maybe the authors, could be sued here.

Present your test results to support your statements. Otherwise, admit your misinterpretation.

I will not post the SAE version on line. Whether or not one is sued, it is not legal; it violates the SAE terms of service, and the rules of this site.

[jcl]

Originally Posted by DKB_SATX

FUD. The clear statement is that taking TOO MUCH load off the rear axle (vastly more than recommended by modern manufacturers) is indeed problematic, but taking reasonable amounts (in the range of 50% FALR) achieves both load-leveling and reduced understeer, improved braking for trailers with electric brakes towed by vehicles with a front braking bias (essentially all modern vehicles.) Also clearly expressed is that taking all the tongue weight off the rear axle (which no one recommends doing) is too much and yields negative results. And in his first recommendation (p. 70, E. 1.) he left-handedly recommends the re-examination of slimp dollies (!)

Andy has a RAM HD pickup. The RAM owner's manual has a useful diagram, attached below, which clearly illustrates your point that taking too much load off the rear axle can be problematic.

The top figure shows correct WD; the combination is level.

The second figure shows too little WD; the truck is sagging, the headlights are pointing skywards, and steering will be negatively impacted due to reduced front axle loading. One can visualize how less front (steer) axle traction can result in increased understeer. And with most vehicles designed to understeer already, more understeer should not be the goal.

The third figure shows (vastly) too much WD applied; the truck is raised in the rear. Rear axle traction will be reduced relative to the unloaded/unhitched condition, and this can cause oversteer, with the rear axle breaking loose. This is the condition that Andy is concerned about.

The obvious solution is to apply the correct amount of WD to level the vehicle.

If applying the correct amount of WD creates an unsafe condition and the truck is then prone to oversteer, just imagine how unsafe the vehicle would be to operate when unloaded and unhitched, as it would then have even less load on the rear axle.

[jcl]

Originally Posted by Andy543

Fear Uncertsinity Doubt. That's what sells hitches, isn't it? I would suggest instead that you go with science.

Yes, let's go with science (engineering). The benefits of properly set up WD equipment are well understood by engineers (BASc. Mech; retired P.Eng; former member of SAE)

[Andy543]

While the NHTSA paper shows the negative effects that weight distribution has on towing safety, I would like to point out a couple of other issues with weight distribution hitches. These hitches all increase the distance from the tow vehicle rear axle to the hitch point (some by over 1'), thereby increasing the lever arm that the trailer has to push the tow vehicle around. Secondly, the hitches can be heavy. Extra mass at the hitch point is undesireable because, when subject to the G force of a hard turn, it exerts a horizontal force that pushes on this lever arm. Both of these issues will similarily add to the risk of a jackknife accident.

I don't think we should jump to tell someone to install a weight distribution hitch, when, as in the OP's case, the tow vehicle can easily handle the trailer load without one.

[waninae39]

like any tool or product, the proper installation and usage is key to success.

the WD system setup as shown in the diagram illustrates the proper means to set it up.

it is simple and works as advertised.

improper system is not the products fault

[Andrew T]

This is the article I wrote a few years ago about the J2807 weight distribution recommendation. When the engineers did this testing they were very limited in what they could do. They only had 4 days to do it, only one type of vehicle, one poor off the shelf hitch system and only test track conditions.

https://www.rvlifemag.com/setting-your-torsion-bars/

Earlier in this thread someone mentions that adding weight to the front axle unloads the rear axle. This is not the case we are still adding as much weight to the rear axle as the front as well as moving weight to the trailer axles. Since most tow vehicle storage is in the rear a customer actually loaded for travel will rarely be too light on the rear axle. Still our track testing is done with no cargo load in the vehicle so lighter than would be normal on a trip.

If you watch the video's on our web site you won't fine cases of oversteer even at points where the trailer tires are sliding. We did experience some oversteer with a 2500 truck on our broken pavement section but it was actually worse solo than towing.

https://www.canamrv.ca/towing-expertise/videos/

I hope this helps.

Andy