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Old 04-24-2020, 07:51 PM   #41
jcl
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You can claim it’s out dated and irrelevant if you like but the fact is that all vehicle manufacturers now today limit the amount of WD used for the very reasons stated in that study. Yes it’s still very relevant because the physics hasn’t changed since the study was done.
Recommending 50% or some other FALR target isn’t the same as not using WD equipment. OoS quotes this study to defend his decision not to use WD equipment as required by his tow vehicle manufacturer, when he is not in fact towing with the type of vehicle the study used. That is up to him, but when he recommends the same approach to the broader community, his fallacies should be pointed out so his recommendations can quickly be discounted by those looking for guidance on best practices
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Old 04-24-2020, 08:23 PM   #42
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I tow a 25FB with a 2010 Yukon (short wheelbase, AWD). I originally used a Blue Ox, but switched to an EAZ Lift Elite (plus two friction anti-sway bars) because there was more wiggle going on than we felt comfortable with.


Also, we have found that the feel (perceived stability) of the combination is quite sensitive to the amount of weight distribution we crank in. One hundred pounds plus or minus on the front axle is noticeable. This may be part of why we did not like the Blue Ox: We had 1000 pound bars for it, but the EAZ Lift has 1400 pound bars and we adjust it to put more weight on the front axle than we ever could with the Blue Ox.
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Old 04-25-2020, 04:20 AM   #43
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SSquared's set up is interesting because the relatively high center of gravity, short wheel base, vehicle and trailer weights bring the stability speeds closer to highway speeds than for many of us. Thus the noticeable changes in feel with small adjustments, and different more appropriate components. The Blue Ox 1000 lb tension bars were too flexible for that combination. they required excessive displacement to counteract undesirable forces. It is anecdotal but nevertheless it is evidence of the improvement WD and anti-sway components have on performance and stability at the speeds that matter.

SSquared, if you have not already done so, install stiffer cornering tires. They would help quite a bit at highway speeds. Consider LT tires with higher load ratings or lower profile performance passenger tires. Slightly over inflate them for actual load while towing but don't exceed maximum cold pressure. If you are already at max pressure with your setup, definitely upgrade to a heavier load range.
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Old 04-25-2020, 12:55 PM   #44
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Recommending 50% or some other FALR target isnít the same as not using WD equipment. OoS quotes this study to defend his decision not to use WD equipment as required by his tow vehicle manufacturer, when he is not in fact towing with the type of vehicle the study used. That is up to him, but when he recommends the same approach to the broader community, his fallacies should be pointed out so his recommendations can quickly be discounted by those looking for guidance on best practices
Yes specific vehicles have different tolerances since you do see 0% no rating , 25%, and 50% FALR. Just like 40 years ago most vehicles rear suspension canít react to dynamic road conditions with any significant amount of TW (500lbs +) without the aid of a WDH so itís just not because of RAWR alone.
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Old 04-25-2020, 02:29 PM   #45
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Yes specific vehicles have different tolerances since you do see 0% no rating , 25%, and 50% FALR. Just like 40 years ago most vehicles rear suspension canít react to dynamic road conditions with any significant amount of TW (500lbs +) without the aid of a WDH so itís just not because of RAWR alone.
I haven't seen any manufacture recommend the use of WD equipment with no FALR, it wouldn't make sense. I have seen manufacturers recommend against the use of WD equipment, particularly when the receivers they offer can not withstand the forces imposed by WD equipment. That isn't a comment on how the vehicle handles with or without WD in those cases, it is a comment on the receiver strength. It may also be because the manufacturer has their engineering team in Europe, where WD equipment isn't common, so they simply have no experience with it.

Do you have examples of tow vehicle manufacturers advising in owner's manuals not to use WD equipment with specific reference to concerns over combination vehicle handling?
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Old 04-26-2020, 05:32 AM   #46
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Yes “0% = no rating” Fords new Explorer and Ranger come to mind. There no escaping it, if you want to optimize the two major modes of instability simultaneously then that means very little to no WD applied. This also means that you must have a TV to react to the hitch load used, or greatly reduce hitch load. The SAE TWR is overly optimistic and so is the maximum tongue load they set as it probably takes the vehicle all the way to neutral steer. Also consider new vehicles will use active means to control sway and Understeer Gradient during these tests. A simple way to test this active control is to check the rear brake temps when towing on a windy day. Both my 06 Silverado and the 16 Nissan were activating the rear brakes without any dash indicator since rear brake temps were more than twice the front. This is how vehicle manufacturers get by rating at least new trucks so high.
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Old 04-26-2020, 07:45 AM   #47
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I downloaded and read the 2020 Range Owners Manual and did not see where Ford is advising against use of a WD hitch with a specific reference to vehicle handling.

I do see that they don't mention WD at all. And no wonder, they advise a maximum speed of 62 mph while towing, limit the trailer weight to 7,500 lbs and combined weight to 12,500 lb but then further reduce that by 1,250 lb for every 1,000 feet in elevation above and initial 1000 feet. Thus the vehicle is restricted to towing a 5000 lb trailer no higher than 4000 feet! Quite a capable tow vehicle you found....

The common range of weight distribution is 300-600 lbs returned to the front axle for most real world applications. The statement that [steering and sway] two major modes of instability are optimized with "very little to no WD" is FLAT OUT FALSE. Very little in this context would mean less than 100 lbs and would be achieved with less than 500 lb of combined tension which for most applications provide insufficient yaw damping and far too much remaining understeer for most of the set-ups discussed in this forum at safe towing highway speeds.

Active methods of stability control certainly helps, but it can't correct steering and suspension geometry and COG issues. Passive mechanical methods have their place. They raise the stability speeds above safe travel speeds so you don't encounter the problem in the first place. Active methods detect the onset and reduce the impact after the fact. There is wisdom in the saying an ounce of prevention is worth a pound of cure.
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Old 04-26-2020, 08:38 AM   #48
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"After the fact." Fixes.
A solution that could be all but eliminated with adequate design and execuation...AND, common driving sense while towing, along with a correctly set-up rig.

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Old 04-26-2020, 09:05 AM   #49
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I am sorry this horse has been beat to death, but this is all new to me.

2005 Yukon towing a 2019 23FB flying cloud. Any recommendations on a weight distribution hitch?? I have watched videos on Blue, Ox, Equalizer etc. Should I have dealer just install for big bucks, rent their truck to tow it, or buy it somewhere and have it installed??

Thanks Dan
I am a big fan of the ProPride 3P hitch. Have never had a 'white knuckle' moment even in high cross wind situations. My son and I installed the hitch - pretty easy - forced us to learn the hitches parts, etc. Importantly, ProPride stands behind its products and its people are easily accessible for installation questions, etc. Good luck.
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Old 04-26-2020, 09:26 AM   #50
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Dan, if you are still reading, congratulations on your new trailer. I would simply disregard anything posted by the person who says you should not use a WD hitch. His voice is one of a very few here on the forum.


If you are not comfortable with the dealer selling you a hitch you do have some options. First, you can tow it with your truck without WD if you live close. I probably wouldn't want to do this if I was far away and had to drive at highway speeds.


You can also arrange for it to be towed to some place you feel more comfortable with. Again, this will create some headaches for you.


You can also install it yourself but that is dependent on you mechanical abilities or your perception of these abilities. I have done mine and it isn't really that challenging especially if you follow the instructions. By doing it yourself you can also make small adjustments to get it just right.



Keep up the research on the various brands out there. Each one has its pros and cons but the good ones will all do the job and do it safely regardless of what some might want to say about their personal choice. Best wishes in your search.
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Old 04-26-2020, 11:11 AM   #51
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“ The common range of weight distribution is 300-600 lbs returned to the front axle for most real world applications. The statement that [steering and sway] two major modes of instability are optimized with "very little to no WD" is FLAT OUT FALSE. Very little in this context would mean less than 100 lbs and would be achieved with less than 500 lb of combined tension which for most applications provide insufficient yaw damping and far too much remaining understeer for most of the set-ups discussed in this forum at safe towing highway speeds.”

At this point all I ask is that instead of subjective reasoning that someone provides solid proof that removing 20% of hitch weight off the TV rear axle doesn’t have significant effect on the Understeer Gradient. There’s no doubt that increasing WD tension can increase the sway damping ratio but it comes at the expense of reducing UG. The two modes generally work against each other in that what improves sway damping ratio makes the UG worse and improves UG make sway damping worse. If you successfully satisfy both and find the balance you will most like have a high mass TV that can react to the hitch weight and use minimal to no WD. That really is the only recipe that can handle 900+ lbs of tongue weight and carry the high TW %’s that the RV TT requires.
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Old 04-26-2020, 11:49 AM   #52
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Yes ď0% = no ratingĒ Fords new Explorer and Ranger come to mind. There no escaping it, if you want to optimize the two major modes of instability simultaneously then that means very little to no WD applied. This also means that you must have a TV to react to the hitch load used, or greatly reduce hitch load. The SAE TWR is overly optimistic and so is the maximum tongue load they set as it probably takes the vehicle all the way to neutral steer. Also consider new vehicles will use active means to control sway and Understeer Gradient during these tests. A simple way to test this active control is to check the rear brake temps when towing on a windy day. Both my 06 Silverado and the 16 Nissan were activating the rear brakes without any dash indicator since rear brake temps were more than twice the front. This is how vehicle manufacturers get by rating at least new trucks so high.

Ford does not recommend 0% for the 2020 Explorer. Read the manual. You have taken their silence on the use of WD to be a recommendation not to use it. Absence of proof is not proof of absence. Surely if Ford was as concerned as you suggest, then they would have cautioned against the use WD equipment. But they didnít.

You are projecting.
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Old 04-26-2020, 12:46 PM   #53
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Profxd, you speak about reducing understeer as if it is always undesirable when it is not.

Background

For any curve radius, vehicles with front axle only steering experience under steer at low speeds, transition to optimal neutral steering at what we can call the critical speed, and then at higher speeds, experience oversteer. The Understeer Gradient (UG) Profx is worried about is therefore a function of velocity. This reality is a consequence of the dynamic nature of competing forces and the physical laws. It is due to the difference in slip angle between the front (lower slip angles) and the rear tires.

Vehicles designed for towing or hauling significant loads are all designed with significant understeer when unladen so that as load is added, neutral steering is achieved at speeds well above posted speeds so the roads remain safer for everyone because most drivers react better to understeer.

Consequence:

The ideal situation for a tow set-up is not to maintain the UG of the unladen vehicle , rather it is to maximize neutral steering critical speed for all curvatures you are likely to encounter while towing.

Weight distribution to the front axle and to the trailer axle certainly reduces UG as profxd indicates but what he fails to mention is it also improves overall cornering stiffness so the set-up is able to negotiate corners and swerves safely at higher speeds for all situations with weight distribution properly set up verses too little or no weight distribution. Depending on the set-up, the improvement can be significant, 7-12 mph is not uncommon.

Evidence:

Buried in the engineering study Profxd and out of sight cite are data and graphs that demonstrate improved cornering performance even for the 1970's Nova and Caprice Station Wagon when modest WD is properly applied. The improvements rapidly reverse as too much WD tension is added in a vain attempt to compensate for the reality the vehicles were severely overloaded beyond their capability. I cite this report because it is peer reviewed and published, and Profxd seems to like it.
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Old 04-26-2020, 03:45 PM   #54
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Many posters here complain these disagreements are too technical, with too much theoretical mumbo jumbo, so let me make this practical with a couple examples to demonstrate how this applies to the real world.

an Airstreamer with a stock 2005 Yukon, stock spec tires and a 23' FC FB is in the mountains of Utah happily cruising downhill at posted 65 mph, the driver was of out of sight's mindset and didn't install WD or anti-sway. There was a strong wind from an approaching front but it was steady on the climb. Suddenly going through the canyons it became variable in direction and intensity. The periodicity of the wind set up modest sway conditions but the driver reacted, applied manual trailer braking and was able to control it and proceed by slowing to 50 mph. What would you think might have happened had this person installed a high quality WD anti-sway hitch? What speed would this same set up experience with good sway control?
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Old 04-26-2020, 04:15 PM   #55
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snipsnapqUOT{}&^$..."What speed would this same set up experience with good sway control?"

I'm not sure, I wasn't driving...😂

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Old 04-26-2020, 04:45 PM   #56
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Intersting read ... My owners manual for our 2013 F-150HD FX4 has an enter chapter on the use of WDH and trailer towing. You might be interested in reading my article on the exercise we did in choosing a tow vehicle for our Int'l 25 Airstream and choice of Weight Distrbution/antisway System. IMHO each person really should go through a step by step analysis on this important safety requirement. (my simple 2 cents worth)

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Old 04-27-2020, 05:38 AM   #57
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Profxd, you speak about reducing understeer as if it is always undesirable when it is not.

Background

For any curve radius, vehicles with front axle only steering experience under steer at low speeds, transition to optimal neutral steering at what we can call the critical speed, and then at higher speeds, experience oversteer. The Understeer Gradient (UG) Profx is worried about is therefore a function of velocity. This reality is a consequence of the dynamic nature of competing forces and the physical laws. It is due to the difference in slip angle between the front (lower slip angles) and the rear tires.

Vehicles designed for towing or hauling significant loads are all designed with significant understeer when unladen so that as load is added, neutral steering is achieved at speeds well above posted speeds so the roads remain safer for everyone because most drivers react better to understeer.

Consequence:

The ideal situation for a tow set-up is not to maintain the UG of the unladen vehicle , rather it is to maximize neutral steering critical speed for all curvatures you are likely to encounter while towing.

Weight distribution to the front axle and to the trailer axle certainly reduces UG as profxd indicates but what he fails to mention is it also improves overall cornering stiffness so the set-up is able to negotiate corners and swerves safely at higher speeds for all situations with weight distribution properly set up verses too little or no weight distribution. Depending on the set-up, the improvement can be significant, 7-12 mph is not uncommon.

Evidence:

Buried in the engineering study Profxd and out of sight cite are data and graphs that demonstrate improved cornering performance even for the 1970's Nova and Caprice Station Wagon when modest WD is properly applied. The improvements rapidly reverse as too much WD tension is added in a vain attempt to compensate for the reality the vehicles were severely overloaded beyond their capability. I cite this report because it is peer reviewed and published, and Profxd seems to like it.
“ Profxd, you speak about reducing understeer as if it is always undesirable when it is not. “

This is completely false. A TV that crosses to oversteer is considered by all credible professionals to be in unstable state at that point. You must maintain a positive Understeer gradient while towing. I have the final report submitted to the SAE based on that study. The results are based on how much lateral velocity the combination can handle before the TV oversteer. Lateral velocity of the trailer can occur at anytime, small movements from road conditions, passing vehicles, driver input are just a few. As far as the car you refer to In the study goes, the intermediate car at 4700lbs could not reach 0.3g lateral velocity with a 6000lb trailer with 10% TW. It would jackknife at 0.26g. So again please give us some proof of your interpretation. Where is proof that says this one is completely wrong as you say? Show me and I’ll never mention Understeer Gradient again. Prove that it has no valid impact on towing and high amounts of WD is the key to stability.
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Old 04-27-2020, 05:53 AM   #58
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The application of the tongue load to the vehicle is the primary cause of change in the understeer gradient. Second is the use of a WDH. The best way to maintain Understeer is to minimize WD use or reduce TW.

“ The second most relevant factor which causes a reduction in understeer gradient is the amount of load leveling. Recall that this Is due to the tire's lateral force generating capability, which is proportional to its normal load; consequently, load leveling, which reduces rear tire load, reduces the understeer.”
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Old 04-27-2020, 06:20 AM   #59
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Wow! I consider myself a pretty experienced and educated guy, but these threads boggle my mind. They seem to deteriorate into "mine is bigger than yours" and, like that, I don't really care as long as it brings me pleasure. I suggest that most of us, on this forum, want practical advice on what hitch to buy and how to set it up, for a given TV and trailer combo. We should award a certificate/prize to the first mechanical engineer who refuses to try to prove his expertise and simply gives great advice. It seems that Brian is trying to do that, but keeps getting dragged into the quagmire of theory. I stand by my decision to tow with a 2500 HD and a ProPride hitch!
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Old 04-27-2020, 06:54 AM   #60
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ď Profxd, you speak about reducing understeer as if it is always undesirable when it is not. ď

This is completely false. A TV that crosses to oversteer is considered by all credible professionals to be in unstable state at that point. You must maintain a positive Understeer gradient while towing.
No, it is completely true. Circle where I advocate for negative UG or describe oversteer as desirable. Neutral steering (UG=0) is optimal and will allow a vehicle to negotiate a curve at the highest speed and with the greatest lateral force. do you disagree with that statement? The SAE does not and has no issue with reducing UG so long as it does not become negative in their test scenarios.

The vehicles in the cited study were severely overloaded for their capability and performed very poorly in lateral acceleration tests regardless of WD tension, but they performed better with modest WD as the data and graphs demonstrate than they did with none and with an amount sufficient to unburden the overloaded rear axles.
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