Towing with a Jeep CJ, YJ, TJ, LC FJ-40, LR SIII 80? - Page 3 - Fiberglass RV


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Old 02-23-2007, 10:01 AM   #29
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Pete,

Most Jeeps have a roadblock to the shorter drawbar. The spare tire hangs quite aways off the back. An extended bar seems a necessity.

When my WDH gets here, I am going to have to figure out how to work around this dilema. The shank is "normal" length.
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Old 02-23-2007, 10:18 AM   #30
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Gina, either tow without the spare on the back, or extend the tongue. Extending the draw bar on a short wheelbase vehicle is not a good idea. Every inch of extension makes an unbelievable difference in the amount of leverage the trailer tongue can exert on your Jeep. I don't believe it's a linear progression. I shortened my drawbar just two inches for one trailer behind a raised, short-wheelbase Toyota pickup and that made the rig tow like a completely different vehicle/trailer combo.

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Old 02-23-2007, 10:38 AM   #31
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Pete:

This seems to hit the real crux of the matter, which is wheelbase. With my Ody's 118 inches I have never experienced any tendency for the trailer to fishtail, but I had to replace the stock Honda stinger to get the trailer to ride level. This is what happened:

The hole for the pin put the ball several inches further away from the vehicle. Worked OK but not too reassuring as far as leverage and stresses were concerned. So I took it to a local RV place to have them redrill for the pin a few inches closer to the ball (actually identical with the original Honda spinger). They botched it by drilling a significantly bigger hole than necessary.

However, they acknowledges the error of their ways and replaced the stinger with a new one. Did I want that one drilled? Are you kidding me? (In my hour of need I tested the destroyed stinger on the drill press and discovered it was NOT high-speed steel or some exotic metal workable only with diamond-tipped drill bits. In fact it was mild steel and the bit sliced through there like it was butter. So I drilled it myself).

Well and good. As for your points: well taken, but I must take issue with #3. My intution tells me exactly the opposite. More weight over the rear wheels of the TV is what is neceesary in my book to resist side push. Think of it this way: Imagine taking so much weight off the rear wheels that there is virtually no weight on them at all (part of my aversion to WDH). The result would be completely uncontrollable and the entire rig would flounder around like a drunken sailor. What do you think?
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Old 02-23-2007, 11:34 AM   #32
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Per, my name isn't Pete, but I thought I'd reply anyway.

Actually, you're both right on the axle thing. Overloading the rear axle unloads the front steering axle and can cause vagueness and a lack of control. The load on the hitch uses the rear axle as a fulcrum to leverage it's lateral force against the front axle. If the front axle is already light, it's much easier to lose control. If you unload the rear axle signficantly, the trailer tongue will be able to move it around, again causing a loss of control Having an over or under load situation on either axle isn't a good thing when towing. The purpose of a WDH is not to unload one axle or the other, but to distribute the hitch load equally over both axles returning the vehicle to balance and it's design weight distribution percentages.

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Old 02-23-2007, 01:11 PM   #33
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Roger:

Points well taken. When running down the road with the normally laden trailer the weight on the front axle is in excess of 150 lbs greater than in the rear. That includes the "lightening" of the front brought plus the tongue weight. As I would expect for a front-wheel-drive-engine-over-the-wheels setup.

By my calculations the weight on the tongue (290 lbs) lightened the front axle load by 106 lbs. Changing the stinger back to stock Honda dimensions (see previous post) changes that to 99 lbs. Actually I'm quite comfortable with that, and so far the traction seems acceptably close to stock. There is no doubt that any miscalculations on my part will show up only when the situation is desperate. The airbags bring the suspension travel back to stock, minimizes the weight transfer, improves stability, and keeps the headlights well aimed.
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Old 02-23-2007, 02:05 PM   #34
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A classic example of insufficient tongue weight....

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Old 02-23-2007, 02:16 PM   #35
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When running down the road with the normally laden trailer the weight on the front axle is in excess of 150 lbs greater than in the rear.
Per, I'm not so sure that the issue is either the change in weight or the absolute amounts of weight in pounds on the front and rear axles as much as it is keeping the same proportion of weight by percentage front to rear as the vehicle would normally have from the factory that will maintain proper handling.

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Old 02-23-2007, 02:28 PM   #36
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Pete:

This seems to hit the real crux of the matter, which is wheelbase. With my Ody's 118 inches I have never experienced any tendency for the trailer to fishtail.
And just to add another issue into the fray... a short wheelbase vehicle isn't any more likely to induce trailer sway than a long wheelbase vehicle. Sway is induced by a variety of factors including weight distribution, tongue weight, sidewall stiffness in both the trailer and tow vehicle, wind, and going downhill where the trailer wants to go faster than the tow vehicle. There can also be mechanical issues that allow sway to occur with the tow vehicle such as rear-axle steering if the springs are weak or the spring shackle bushings are worn. Wheelbase doesn't typically enter into the causal factors of sway.

The problem with a short wheelbase vehicle though, is that the shorter the wheelbase the faster things go wrong when they go wrong and the less time you have to correct the problem before you crash.

Generally with a long wheelbase vehicle, you have longer to react because it takes the trailer a longer time to be able to act on and have its way with the tow vehicle, and you can make more gross moves with the longer wheelbase because it doesn't react as quickly. If you make gross moves in a short wheelbase vehicle to try to deal with sway, it's all over before you can correct a second time.

THAT's why 80"-105" wheelbase vehicles are less desireable for towing. When everything is Ok, it's Ok. When it's not, the odds of recovering are poor and the odds of crashing are great.

Roger
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Old 02-23-2007, 03:21 PM   #37
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I think that we are seeing two separate ways in which the ratio between two dimensions is important: the wheelbase, and the distance from ball to rear axle (call it overhang). In both ways, a high ratio of wheelbase to overhang is good. Per touched on one of them: the weight transfer from front to rear axle is reduced if the the ratio is higher. The other reason is that with a higher ratio comes better control of lateral forces. Roger, I agree that short wheelbase doesn't directly cause sway, but higher wheelbase-to-overhang means better ability to control the forces and prevent movement which leads to sway.

Per, I agree with your interpretation of the weight distribution issue. That front axle load with trailer is quite likely still in excess of the front axle load with just a driver - it's not as if the front end is floating around with no traction.

Roger, I do not agree that the original weight distribution should be maintained. The distribution when empty of any van or truck is normally front-heavy, and the load is primarily carried nearer the back axle than the front... so distribution shifts rearward as load is increased. This is normal, expected, and accounted for in the design and selection of tires and suspension components. For instance, no one would suggest that a dually pickup should be loaded so it stays 60% front-heavy, and they certainly handle better when carrying a load in the box. Most front-drive sedans have a lower allowed axle load (GAWR) in the rear than the front, but for my Sienna front and rear GAWR are equal, because it is expected to carry far more passenger and cargo load than a sedan, further back. There is no way to carry the rated payload in vans such as the Sienna and Odyssey - or I assume even the beloved Astro - and both maintain the empty weight distribution and not overload the front axle.
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Old 02-23-2007, 03:32 PM   #38
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...The purpose of a WDH is not to unload one axle or the other, but to distribute the hitch load equally over both axles returning the vehicle to balance and it's design weight distribution percentages.
While I respect the experience of those members who are dedicated to [b]WD hitch systems, I must fundamentally disagree with the notion that their primary purpose is to do anything except unload the rear axle. The spring bars transfer load from the rear axle to the other axles, and the various springs, cams, sticky pivots, and whatever else makes a "sway control system" just try to patch the problems of the trailer and tow vehicle suspensions. Putting the tire traction anywhere other than where the mass is located just does not make sense.

To think of it another way: the [b]design weight distribution percentages for the loaded condition are not the same as for the unloaded condition, and depend on the type of vehicle and its intended use. The design intent of a truck or van includes most of the payload being carried by the rear axle, not evenly distributed - or even worse, distributed 60% front and 40% rear as you would get by maintaining the unloaded distribution ratio.

Due to poor wheelbase-to-overhang ratios, and resulting weight transfer from front axle to rear, short tugs can easily overload the rear axle. Even my 120" wheelbase van would overload the rear axle with a moderate (bigger than ours) travel trailer; it happens at a lower tongue weight with the short tug. Thus the WD requirement, and poor control due to overloaded rear tires, springs, shocks, and suspension bushings.
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Old 02-23-2007, 05:03 PM   #39
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While I respect the experience of those members who are dedicated to WD hitch systems...


To think of it another way: the [b]design weight distribution percentages for the loaded condition are not the same as for the unloaded condition, and depend on the type of vehicle and its intended use. The design intent of a truck or van includes most of the payload being carried by the rear axle, not evenly distributed - or even worse, distributed 60% front and 40% rear as you would get by maintaining the unloaded distribution ratio.
Brian, the only flaw I can see in your thoughts is that a trailer tongue weight load ISN'T over the axle; it's load exerts leverage several feet aft of the axle, a problem overcome by the 5th wheel setup. Not only does a trailer tongue weight overload the rear axle, equally important is that it UNLOADS the front axle using the rear axle as a lever. Weight distributing hitches tend to counter that.

I'm not a physicist and theoretical calculations and discussions cause me to fall immediately into the "MEGO" Syndrome (My Eyes Glaze Over) but I can tell you without hesitation that I'm much more comfortable towing my 17' Bigfoot with my Tundra using a WDH and sway control than on a bare ball with sway control even though the trailer is well behaved on a bare ball alone. There is a significant difference in the handling of the truck between the two methods, even though the trailer is at about half of the rated towing capacity of the truck and the tongue weight falls well below the rated capacity of the hitch (in other words, well below it's design limits).

I agree that sway control can mask problems if they're not resolved at the source, but there's absolutely no reason not to a WDH system for redistributing tongue weight load on a tow vehicle/trailer combination that can benefit from it.

There is no doubt that vehicles are designed to handle properly throughout a "range load", but if it's possible to make adjustments to improve the handling while towing (whether it's FWD or RWD) why would you not want to take the opportunity to do it?

And frankly, once the causes of sway have been dealt with appropriately, there is no better way to counter unforseen sway causes (sudden loss of tire pressure... whatever) than having sway control installed (presuming that one understands both the benefits and shortcomings of the sway control system they choose).

This is truly one of those areas that you need to have experience under your tires in a variety of towing cirumstances with a variety of tow vehicles and trailers and with and without WDH and sway control in their various incarnations to truly appreciate. Until you have that, you'll just have to take our word that they're valuable and an asset. I'm glad your setup works for you, and that so far you've not had any problems. But, like riding a motorcycle, it's said there are two kinds of riders: those who've crashed, and those who are about to. Towing isn't much different. After you experience a signficant towing incident, you'll come to appreciate that equipment that can give you an edge when you need it most.

Roger
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Old 02-23-2007, 05:11 PM   #40
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I can't wait (Excuse the pun, I'll be in my room..) to try my WDH. I have been told by everyone that it will make a night and day difference in the handling of the vehicle, and with that in mind alone, it seems a good idea.
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Old 02-23-2007, 06:09 PM   #41
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I think that we are seeing two separate ways in which the [b]ratio between two dimensions is important: the wheelbase, and the distance from ball to rear axle (call it overhang). In both ways, a high ratio of wheelbase to overhang is good.
I'm with Brian on this. I suspect that it is the ratio of overhang to wheelbase that matters, not just the wheelbase itself.

I've only towed an empty boat trailer with a 90" Land Rover Defender (the old model that you don't get any more), but still 1500lb and it was utterly effortless (well, in stability, not power) - but then if you look at a picture of a short wheelbase Land Rover, you'll see the rear end is only a few inches, quite literally, behind that back edge of the rear tyres.

I've asked experienced LR Defender tow-ers about this and found some guys who prefered the 90" (with very short overhang) and some who prefered the 110" (with longer overhang), so that's not much help!!!

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Old 02-23-2007, 06:35 PM   #42
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Wow, after reading all of this I think I'm going to stay in a hotel from now on! Maybe I should get a truck big enough to carry my Scamp in the back so I don't have to pull it
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