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Old 01-10-2013, 04:19 PM   #1
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Towing questions

(1) If your trailer has 4 wheels / 2 axles, what is it's tongue weight? Does tongue weight really come in as a factor anymore - it will only be the weight of the connecting arm right?

(2) Towing capacity of a vehicle is stated by the manufacturer. For instance for the 4.10 JKU it's 3500lbs. How exactly is this figure arrived at? The entire weight of the trailer(W) is not supported by the jeep esp if the trailer has two axles. On a perfectly flat surface, the only load on the jeep is the rolling resistance of the trailer(R). At an incline, this will increase to include a cosine component of the trailer weight (R+W*cos(Angle)). If I understand right, the jeep should be able to keep pulling this load. I take it there's an "nominal" industry upper bound on how steep the incline on which we're towing can be, and from this we compute W by equating (R+W*cos(max.angle)) to the maximum load that the jeep can bear (padding included everywhere). Then the manufacturer would round this lower and publish it.. So, if the inclines on which we're towing is severely low, a vehicle can safely tow significantly more than the tow rating.. (I'm not talking of stopping power, let's assume the trailer has supernatural brakes which ARE 100% able to stop it). Or am I wrong in my thinking here?

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Old 01-10-2013, 04:40 PM   #2
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Yay! Trig!!!

I'm sure they are going by the average conditions without exceeding a certain workload on the engine/brakes...

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Old 01-10-2013, 05:33 PM   #3
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Tongue weight is roughly 10% of trailer dry weight (rule of thumb)
That weight is always present and is a significant factor. It produces a torsional load on the tow vehicle frame
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Old 01-10-2013, 06:03 PM   #4
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A lot if times maximum trailer weights don't have anything to so with the capability of the vehicle to pull but to stop. Jeeps have short wheel bases and a heavy trailer can push the rear end sideways in a heavy braking situation. An overloaded tongue can raise the front end causing an inability to steer. Been there, done that.
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Old 01-10-2013, 06:12 PM   #5
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For safe towing, most trailers require at least 10% of the trailer weight on the tongue, a 3500lb load should have tongue weight of at least 350lbs. A trailer that heavy should also have supplemental brakes as required by most states now. But as others have said, with the short wheel base, towing weight will drop.
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Old 01-10-2013, 07:14 PM   #6
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The tongue weight having to keep the trailer on the ball doesn't come up if one uses a D ring or some other hook up other than a ball.

I'm purely talking of two axle self-stable trailer with good trailer brakes. In that case what is the tongue weight? If you put the tongue on a scale up on a block so the scale is the same level as the hitch (the old fashioned way of finding tongue weight) the only weight that the scale would read would be a majority portion of the weight of the tongue arm.
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Old 01-10-2013, 08:08 PM   #7
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Quote:
Originally Posted by mathew85
the only weight that the scale would read would be a majority portion of the weight of the tongue arm.
Correct. But the tongue weight rating on the jeep is a working load. No one cares if you put 50,000lbs or 5lbs if the jeep isn't moving. So you'd have to take into account balancing the load on the trailer so you don't overload the tongue. I know I've overloaded it and it jus doesn't drive as well.

The actual towing capacity is a gross combined vehicle weight. It's calculated with just the driver(no passengers) all stock tires, a full tank of gas, and a trailer. If they say the total weight it shouldn't exceed is X then X-(weight of vehicle+driver)=tow capacity and for an unlimited it's 3500lbs, 2000lbs for a 2dr.

The jeep can pull way more than that (I pulled an F350 dually with my 2dr) But can it stop it? And if it can't that makes you liable for accidents.

That being said you make the educated decision. A few hundred over wont make a big deal. A few thousand is noticeable and could be a problem. Trailer brakes will help but if its the hydraulic sleeve kind like on many trailers today they still have to push on the vehicle to activate them which can send the rear of a wrangler out
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Old 01-10-2013, 08:17 PM   #8
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Originally Posted by mathew85 View Post
The tongue weight having to keep the trailer on the ball doesn't come up if one uses a D ring or some other hook up other than a ball.

I'm purely talking of two axle self-stable trailer with good trailer brakes. In that case what is the tongue weight? If you put the tongue on a scale up on a block so the scale is the same level as the hitch (the old fashioned way of finding tongue weight) the only weight that the scale would read would be a majority portion of the weight of the tongue arm.
Unless I am reading something into your first statement here, one must ALWAYS have a "tongue heavy" load. If you get too light on the tongue, I can just about guarantee that you are going to have big time problems..
A bit of advice is that if you do not have experience towing to start small and get accustomed to all the dynamics involved. And don't over think it.
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Old 01-10-2013, 09:17 PM   #9
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I hope to god this guy isn't from SoCal so my family and I won't be on the road with him!
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Old 01-10-2013, 11:32 PM   #10
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OP You are wrong in your thinking. The tow limits are based on vehicle dynamics and safety during non-standard maneuvers.

The manufacturers use proprietary formulas, testing, marketing, and legal consultation to determine towing capacity, at least until recently. The Society of Automotive Engineers has developed a new standardized testing procedure, including actual vehicle testing and performance measures. This SAE procedure is supposed to be adopted by all manufacturers, but that is still ongoing. This was done partly to stop the marketing wars where the manufacturers were bumping up the tow ratings of their 1/2 ton trucks to compete for sales numbers. I'm not sure if Chrysler is fully onboard yet or not.

The Jeep Wrangler is a poor tow vehicle because of the suspension and chasis dynamics. The JKs long travel coil spring suspension is great for off road articulation, but does not do a good job of handling the dynamic forces that come from a loaded trailer in stopping or avoidance maneuvers.

Tongue weight is dependent on how the trailer is loaded. If you put all your stuff in the front of the trailer, it'll be tongue heavy, if you put it in the back, it'll be tongue light. It is generally recommended that tongue weight equal 10-20 percent of the total trailer weight. At the same time the tongue weight should not exceed the maximum allowable tongue weight in your owners manual.

If the tongue weight is too light, the trailer will bounce and be hard to control. If it is too heavy, it can unweight the front tires, making it difficult or impossible to steer the tow vehicle.

Their are devices to help control heavier tongue weights including load equalizing hitches and rear airbags that go inside the coil springs. The air bags in particular are a great low cost solution, but you are still limited by the vehicles towing capacity.

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Old 01-11-2013, 12:08 PM   #11
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OP. One final comment. Your equations are for a simple stationary object, on the verge of exceeding rolling resistance. Put your text book away. It does not apply to an object actually in motion.
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Old 01-11-2013, 12:27 PM   #12
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I can't believe nobody has mentioned that where the axles are mounted makes all the difference in the world. NO math equation is going to give you a tongue weight unless you have measurements off the trailer in question.

And yes, the JK and JKU are severely under-rated. They can tow a lot more than the manual says they can legally tow. Wheelbase isn't why either... just look at WK2 and KK Jeeps...same or shorter wheelbase with thousands more towing capacity.
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Old 01-11-2013, 12:31 PM   #13
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Quote:
Originally Posted by mathew85 View Post
The tongue weight having to keep the trailer on the ball doesn't come up if one uses a D ring or some other hook up other than a ball.

I'm purely talking of two axle self-stable trailer with good trailer brakes. In that case what is the tongue weight? If you put the tongue on a scale up on a block so the scale is the same level as the hitch (the old fashioned way of finding tongue weight) the only weight that the scale would read would be a majority portion of the weight of the tongue arm.
Tongue weight has nothing to do with "keeping the trailer on the ball" it has to do with handling....If your tongue weight is really light the trailer will sway to the point it will flip, same with a trailer weight too much for the tow vehicle....I have seen both and they ain't pretty.......
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Old 01-11-2013, 12:54 PM   #14
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Here are some good resources if you are interested in the facts instead of the opinions expressed above.

http://rvsupertramp.com.au/Portals/0...ynamics_cw.pdf

http://people.bath.ac.uk/en8cjk/Caravan.pdf

http://www.caranddriver.com/features...ined-tech-dept


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Old 01-11-2013, 01:48 PM   #15
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I hope to god this guy isn't from SoCal so my family and I won't be on the road with him!
Hey Mr! The toyota tundra towed a space shuttle in your own home state California!

I've held the opinion that most Californians have a character problem.. you confirm!
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Old 01-11-2013, 01:50 PM   #16
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Thanks Mike. This is the kind of information I was hoping to get through an informed and intelligent discussion. Unfortunately some people just don't like questioning their ossified beliefs.
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Old 01-11-2013, 02:25 PM   #17
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This link confirms what I thought as the basis. The grade factor is one big concern when towing.

But the yaw stability mentioned in the first link is very good to know, and like the first link clearly outlines, while tongue weight can be used as a ballpark for a single axle trailer, it's not exactly the thing one wants to look at.

And like I was speculating, the base flat surface pulling power of a vehicle like the wrangler is many orders of magnitude more than the tow rating - and at slow speeds without external influences like wind, and on a purely flat surface, a heavier load can be moved by such a vehicle - which explains why a space shuttle can be towed by something like a tundra.

But when speeds get higher, risk of external influences producing yaw becomes a significant concern.

Likewise, at any grade above a flat surface, the gravitational force also becomes a load on the towing vehicle.

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Old 01-11-2013, 05:36 PM   #18
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Hey Mr! The toyota tundra towed a space shuttle in your own home state California!

I've held the opinion that most Californians have a character problem.. you confirm!
You correct. It towed it under 3mph with security all around it. Great comparison Einstein.
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Old 01-12-2013, 05:07 AM   #19
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OK, Matthew; I am trying to be helpful here. There are many different factors that come into play when towing. Are we towing a camper/ enclosed trailer, or a flatbed with a pallet of heavy material. If it is a camper/enclosed trailer, side winds play a huge factor in how trailers react, especially at speed. The flatbed with a low heavy load, on the other hand, will not be such a hand full. Also, The configuration of the towing vehicle comes into play. A JEEP with a short wheelbase/ high profile will react differently than my F250 long wheelbase/ with a relatively low profile, especially in side winds/cross winds. Then you get to going through some canyons/cuts where the wind is hitting you hard from one direction, and in a distance of a few feet, the wind hits you from another direction. These are just a few of the things to contend with when towing, so please, I am not trying to be a smart ass when I say start small/ light and gain some experience before trying to tow the max load with something like a JEEP.
Also, on an other note, when the manufacturers put out their load ratings; they are looking at the liability factor. Their attorneys are trying to make them as "lawyer proof" as possible in this day and age where every time something bad happens, we go out and sue somebody for our own stupidity. I am not saying this is what you are going to do, but there are plenty that do. McDonalds and hot coffee come to mind.
Best Regards to you and yours. Above all, enjoy your JEEP.
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Old 01-12-2013, 10:31 AM   #20
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(1) that is a very rare trailer configuration. Are you actually planning to do this or is this just a hypothetical?

As mentioned already even dual or triple axle trailers with the axles placed together should have a 10% tongue weight (3500 lb trailer = 350 lb tongue weight)

Or are you talking about a trailer like the image I've attached? That would have a very minimum tongue weight and a very high load carrying capacity, but I can't remember seeing one on the road. I have seen them on the farm used behind a tractor. I personally would have no actual knowledge of the safety of one of these at speed on the road behind a Jeep.

I have to say I'm just really curious what you are wanting to do?
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Old 01-12-2013, 10:46 AM   #21
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(2) if you're interested in a normal towing situation like a utility, boat, or some type of RV trailer I agree with Don above. It's best not to start out at or above a vehicles Max Tow Rating when you're learning. (You may have towed a ton I'm not saying you are new to towing, I just don't know) also, every trailer / load is somewhat unique. I mostly tow a 3500 lb boat so I'll give you my impressions of that....

A lot of us would love to really know the limiting factor that keeps the JKU rating at 3500 lbs (maybe some do know and it's just me that hasn't heard).

My old 1997 jeep cherokee had a tow rating of 5000lbs (with a shorter wheelbase, solid axles and weaker engine than a JKU). I can tell you that towing 5000lbs with it was down right scary. I regularly towed a 3500 lb boat with it that had hydraulic disc brakes and it was acceptable.

I still have a 3500 lb boat. My tow vehicles are a towing equipped Toyota Sienna van and a max tow package Wrangler Unlimited Sahara. The van towing that load I would consider acceptable, in about the same league as the old cherokee on the road with a little better braking, but considerably worse on a boat ramp because of front wheel drive and no 4x4 low range.

My 2012 Wrangler unlimited is vastly superior to both the Sienna and Cherokee the with the same load. It definitely has more power, stability and braking than the Sienna with the same max rating.

The only other vehicles I've towed with a good bit would be a Chevy Tahoe and a full size Chevy low top conversion van. Both of those vehicles have tow ratings above 8000 lbs. The Wrangler is at a power disadvantage to both of these so it's a little slower, but with a 3500 lb load it feels about the same in my opinion. Feels just as safe braking and in normal on the highway use. Please keep in mind I'm NOT comparing it to those vehicles at their max capacity, just at the wranglers max capacity.

I feel completely safe doing a lot of towing at the JKU Max Capacity. I however do not exceed it even though I think it could tow more because I don't know the limiting factor and don't want to be liable for exceeding the tow rating. The toughest limiting factor on the SAE test linked to earlier is probably the acceleration tests.

As for your heavy math thoughts here's something I've noticed about the wrangler... The rear axle is very close to the rear of the vehicle so the trailer should have less leverage on the vehicle than almost any other vehicle on the road. I think that's one possible reason that a trailer feels very stable to me behind my JKU
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Old 01-14-2013, 12:15 AM   #22
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OK, Matthew; I am trying to be helpful here. There are many different factors that come into play when towing. Are we towing a camper/ enclosed trailer, or a flatbed with a pallet of heavy material. If it is a camper/enclosed trailer, side winds play a huge factor in how trailers react, especially at speed. The flatbed with a low heavy load, on the other hand, will not be such a hand full. Also, The configuration of the towing vehicle comes into play. A JEEP with a short wheelbase/ high profile will react differently than my F250 long wheelbase/ with a relatively low profile, especially in side winds/cross winds. Then you get to going through some canyons/cuts where the wind is hitting you hard from one direction, and in a distance of a few feet, the wind hits you from another direction. These are just a few of the things to contend with when towing, so please, I am not trying to be a smart ass when I say start small/ light and gain some experience before trying to tow the max load with something like a JEEP.
Also, on an other note, when the manufacturers put out their load ratings; they are looking at the liability factor. Their attorneys are trying to make them as "lawyer proof" as possible in this day and age where every time something bad happens, we go out and sue somebody for our own stupidity. I am not saying this is what you are going to do, but there are plenty that do. McDonalds and hot coffee come to mind.
Best Regards to you and yours. Above all, enjoy your JEEP.
Thanks Jeepdon. I really appreciate the advice; and I _am_ a very careful person(!!). I will start small and don't plan to tow something big the very first time (albeit all the people that seem to have assumed otherwise on this thread).

But I also am a person that likes to know as much as I can about what I am going to do before I do something - in the hope that knowledge will help avoid stupid endeavors. And I really appreciate everyone who gave explanations about the sideways sway, wind stability etc factors. Helps me understand better!
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Old 01-14-2013, 12:23 AM   #23
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Are you actually planning to do this or is this just a hypothetical?
It is hypothetical. I don't plan to do this, definitely not in the foreseeable future.

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Or are you talking about a trailer like the image I've attached? That would have a very minimum tongue weight and a very high load carrying capacity,
Yes, that's kind of what I am talking about.

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I have to say I'm just really curious what you are wanting to do?
I am not trying to do anything.. I'm just trying to understand how the tow-rating is arrived at, and understand the different aspects that one should consider as far as towing is concerned. A blind 3500lb max load and 350 lb tongue weight seemed misleading to me. I'd imagine there are configurations under which it can tow more, and configurations under which the 3500/350 even will be unsafe.

I read your second post as well and really appreciate your taking the time to write it down. Yes, I am new to towing. What I would eventually be towing would be a sailboat, and I don't expect it to exceed the tow rating. That part about the rear axle being close to the rear is an interesting point you make too! Thanks much for the feedback.
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Old 01-14-2013, 12:25 AM   #24
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Great comparison Einstein.
Go read my original post smarty pants. Then you'll see that that was precisely what I was asking about!
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Old 01-14-2013, 04:38 AM   #25
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The trailers that are configured like the one in AUskier's post are called a "Wiggle Wagon" by truckers for a reason. But if you can learn to handle one of these, they work pretty good in most situations. There a lot of people that think they can't be backed up, but once you learn how, it is not too difficult. And myself, I would not put anything with a high profile on it, and pull it at speed. Companies like Consolidated Freightways (now non-existent) pulled them down the Interstate Highway system 3 at a time where legal (known as triples); but as soon as the wind came up, or the weather got bad, they would have to drop at least one trailer.

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