tow bar length: how long is good? - Fiberglass RV
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Old 02-15-2023, 01:03 PM   #1
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Name: zack
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California
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tow bar length: how long is good?

I have been towing a lot for the last 4 years or so and I think I understand ball height and things like that, but I feel a pretty uncertain about the considerations and trade-offs associated with tow-bar length. Right now I have a 12.25" long ball mount (see pictures) which I use to tow a Scamp 13 with an old Toyota 4Runner. I am thinking about getting a new longer bar to create more space, enable tighter turns and especially allow rear hatch opening when parked at an angle. What are the tradeoffs I need to consider? How long can I reasonably make that distance from the receiver to the tow ball?

The Scamp weights about 1500 lbs and has a group 27 battery and two propane tanks on the tongue.
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Old 02-15-2023, 02:12 PM   #2
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Think about the principle of leverage."Give me a place to stand, and I can move the Earth," said Archimedes. All it requires is a very long lever. By extending the hitch ball farther from the vehicle's rear axle, you lengthen that lever. That increases the vertical force when your trailer tongue jigs up and down. That's a bad thing for handling and safety.

The prior owner of my Scamp used an extension so he could drop the tailgate of his Honda pickup without hitting the hitch. When I mentioned this to the guys at Can-Am Trailers, they scoffed, "We won't do that kind of installation." They say that one of the most critical measures in towing is the ratio of vehicle wheelbase to the distance between rear axle and hitching point. That distance should be kept as low as possible- which is why they generally recommend SUVs over pickups for towing compact travel trailers. The short rear overhang of SUVs, designed for good offroad departure angles, may be their hidden advantage.
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Old 02-15-2023, 03:23 PM   #3
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I have a Ultimate Jack on our Casita so that I can open the truck tailgate with the trailer hooked up. Others like the Jack-me-Up device where the tongue jack easily pops off. Because of the leverage principal I keep my ball mount as short as possible, even drilled another hole in it so I could move it in closer to the bumper.
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Old 02-15-2023, 05:35 PM   #4
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Quote:
Originally Posted by mary and bob View Post
I have a Ultimate Jack on our Casita so that I can open the truck tailgate with the trailer hooked up. Others like the Jack-me-Up device where the tongue jack easily pops off. Because of the leverage principal I keep my ball mount as short as possible, even drilled another hole in it so I could move it in closer to the bumper.
I do appreciate the words of caution and the leverage principle. (force times distance is torque?)
I guess what I was hoping is that, because my Scamp 13 is very lightweight, I could extend back further and reap some benefit from that in terms of maneuverability and clearance.
So I guess I am wondering, with half the weight of some trailers, maybe it could be safe for me to go back twice as far? Does anyone agree with that?
For example, they sell a 16 inch tow bar (aka ball mount, aka draw bar) rated to 6000 lbs...(see picture below) Is that safe for my rig? (4Runner--Scamp13)
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Old 02-15-2023, 06:43 PM   #5
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It's not so much the ball mount capacity, the leverage effect is on your vehicle receiver, it's mounting bolts, and the points where it is attached.
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Old 02-15-2023, 06:51 PM   #6
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I have the Curt that you described in the first post on my Ford Ranger. I used a standard length, but couldn't open my tailgate. The longer one allows me to open my tailgate all the way.
I don't notice any difference in towing, although I do understand the concept of leverage, both vertical and horizontal. In my case, based on distance to the fulcrum (rear wheels to 2" ball) it changed the 53 1/2" on the shorter ball mount, to 58 1/4" on the longer ball mount to the rear wheel pivot point. That's less than a 10% increase in leverage, so if I was anywhere close to my max tongue weight of 750 lbs I would reduce my tongue weight by 10% or more to be safe.
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Old 02-15-2023, 08:54 PM   #7
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Quote:
Originally Posted by Radar1 View Post
it changed the 53 1/2" on the shorter ball mount, to 58 1/4" on the longer ball mount to the rear wheel pivot point. That's less than a 10% increase in leverage, so if I was anywhere close to my max tongue weight of 750 lbs I would reduce my tongue weight by 10% or more to be safe.
But that's not how it works.

The tongue weight limit is based on the standard location of the ball in reference to somewhere on the vehicle. If you measure from the hitch pin, change that by 1 inch it might reduce your tongue weight by half.

So, I'm doubtful that adding ten percent to the distance between the ball and the center of the rear axle will only increase your hitch loading by ten percent.

But who knows? It's completely determined by the unknown process vehicle manufacturers go through to determine towing capacity.

I don't think it's safe, but that's me.
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Old 02-15-2023, 10:39 PM   #8
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Could you lengthen the frame on the trailer enough to open the rear hatch?
Me , I'd figure out how much longer the bar needs to be to open the hatch and try it first. Percentage wise it can't be that big a change,,,? Your not dealing with a triple axle here.
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Old 02-16-2023, 07:22 AM   #9
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Keep the tow bar length as short as you can. You mention you wish "...to create more space, enable tighter turns and especially allow rear hatch opening..."

More space: Yes, a longer bar will CONSUME (not 'create') more length for the car and trailer, but I think your 'create more space' was for access in the hitch area for the rear of the tow-er, and the front of the trailer, and the longer bar will do this.

Enable tighter turns: Yes, and also, No. You will be able to make a sharper angle before the rear corner of the tow-er comes into the front corner of the trailer with a longer distance between them due to the longer tow bar, but the total combined length is also increased. That can mean having to take wider swings at right angle turns putting the front of the tow car into another lane and still risk having the trailer wheel run up on the curb.
Higher than city speed turns (like a lane change on the highway) may be less secure due to the initial reverse turn at the ball starting the trailer even further in the opposite direction before it changes to follow the tow car direction. Turning left will move the tow ball to the right. The tow car in front of the rear axle moves left immediately, but the parts behind the rear axle move right first, then change to follow left. The further behind this rear axle pivot center, the more right, then left the movement. Think of how the tail end on a 747 swings as the plane's nose wheel moves. Starting the trailer in one direction opposite the direction the tow car is turning than having to reverse that momentum to follow the tow car could lead to unexpected handling situations.

Allow access to hatch opening: A longer tow bar, as pointed out in the 'more space' comment will accomplish this.


But that's just the geometry. The tongue load, as Mary and Bob, and AlanK mention, isn't based on rear axle location, but on the center of the receiver's attachment to the tow car to the ball. It's THAT distance that need to be considered when calculating tongue forces.
If the tongue load were calculated with an 8 inch bar, and the pin to receiver attachment center were 4 inches further forward on the tow car's frame, then the ball would be 12 inches back from the frame attachment. A 200 lb tongue load would be a lever of 200 lb at one foot, 200 lb*ft on the receiver to frame attachment.
Increase that tow bar by 8 more inches and that ball is now 20 inches (1.667 ft) back from the receiver's attachment points. A 200 pound tongue at that distance is now 333 lb*ft of lever on the receiver to frame attachment.

Zack, can the items on the tongue be repositioned to permit rear hatch clearance? Taller tanks put back as far as possible from the hitch and shorter battery in front, but as far back as the tanks would allow?
Is clearance to the battery the issue? Are two tanks needed? Could one as far back as possible, and the battery alongside, be an option?
How close is it? Would an inch or two of draw bar drop lower the tanks enough for the hatch edge to just clear above them?
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Old 02-16-2023, 09:09 AM   #10
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Question

Quote:
Originally Posted by John McMillin View Post
Think about the principle of leverage."Give me a place to stand, and I can move the Earth," said Archimedes. All it requires is a very long lever. By extending the hitch ball farther from the vehicle's rear axle, you lengthen that lever. That increases the vertical force when your trailer tongue jigs up and down. That's a bad thing for handling and safety.

The prior owner of my Scamp used an extension so he could drop the tailgate of his Honda pickup without hitting the hitch. When I mentioned this to the guys at Can-Am Trailers, they scoffed, "We won't do that kind of installation." They say that one of the most critical measures in towing is the ratio of vehicle wheelbase to the distance between rear axle and hitching point. That distance should be kept as low as possible- which is why they generally recommend SUVs over pickups for towing compact travel trailers. The short rear overhang of SUVs, designed for good offroad departure angles, may be their hidden advantage.
This helps explain why towing our Trillium 4500 with our 2022 Model Y Long Range seems much more secure than our 2015 Odyssey. Both vehicles have a 3500 pound tow capacity and nearly the same curb weight, but the Model Y has a much shorter distance from the rear axle to the lip of the hitch receiver (34 inches vs 45 1/2 inches). All wheel drive helps too.
The Odyssey performed well as a tow vehicle and you can't beat the huge cargo space, so we are holding on to it as backup and occasional driver.
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Old 02-16-2023, 09:34 AM   #11
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Name: zack
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Quote:
Originally Posted by Jon MB View Post
Keep the tow bar length as short as you can. You mention you wish "...to create more space, enable tighter turns and especially allow rear hatch opening..."

More space: Yes, a longer bar will CONSUME (not 'create') more length for the car and trailer, but I think your 'create more space' was for access in the hitch area for the rear of the tow-er, and the front of the trailer, and the longer bar will do this.

Enable tighter turns: Yes, and also, No. You will be able to make a sharper angle before the rear corner of the tow-er comes into the front corner of the trailer with a longer distance between them due to the longer tow bar, but the total combined length is also increased. That can mean having to take wider swings at right angle turns putting the front of the tow car into another lane and still risk having the trailer wheel run up on the curb.
Higher than city speed turns (like a lane change on the highway) may be less secure due to the initial reverse turn at the ball starting the trailer even further in the opposite direction before it changes to follow the tow car direction. Turning left will move the tow ball to the right. The tow car in front of the rear axle moves left immediately, but the parts behind the rear axle move right first, then change to follow left. The further behind this rear axle pivot center, the more right, then left the movement. Think of how the tail end on a 747 swings as the plane's nose wheel moves. Starting the trailer in one direction opposite the direction the tow car is turning than having to reverse that momentum to follow the tow car could lead to unexpected handling situations.

Allow access to hatch opening: A longer tow bar, as pointed out in the 'more space' comment will accomplish this.


But that's just the geometry. The tongue load, as Mary and Bob, and AlanK mention, isn't based on rear axle location, but on the center of the receiver's attachment to the tow car to the ball. It's THAT distance that need to be considered when calculating tongue forces.
If the tongue load were calculated with an 8 inch bar, and the pin to receiver attachment center were 4 inches further forward on the tow car's frame, then the ball would be 12 inches back from the frame attachment. A 200 lb tongue load would be a lever of 200 lb at one foot, 200 lb*ft on the receiver to frame attachment.
Increase that tow bar by 8 more inches and that ball is now 20 inches (1.667 ft) back from the receiver's attachment points. A 200 pound tongue at that distance is now 333 lb*ft of lever on the receiver to frame attachment.

Zack, can the items on the tongue be repositioned to permit rear hatch clearance? Taller tanks put back as far as possible from the hitch and shorter battery in front, but as far back as the tanks would allow?
Is clearance to the battery the issue? Are two tanks needed? Could one as far back as possible, and the battery alongside, be an option?
How close is it? Would an inch or two of draw bar drop lower the tanks enough for the hatch edge to just clear above them?
Jon, Thank you so much for this deeply thoughtful and well-informed reply. You have given me a lot to think about. I really appreciate that. I feel like now I can consider the consequences in a much more nuanced and informed way. I see what you mean about maneuvering. Already I have to be careful when I am parked next to a stand of trees as I am leaving, as I turn away from them that swings the front of the trailer toward them. I have to sometimes steer the TV toward the trees to get the trailer-front away from them, etc.

A key issue for me is that I often park/camp with an angle between TV and Scamp. Sometimes it is the geometry of the camp site that dictates that, but also it is preferable for me because I have a big front window in the Scamp and I get a much better view with the 4Runner (TV) out of the way. When the angle is a bit to much (maybe more than about 45 degrees), I can't open the rear hatch of the 4R, and that is inconvenient. So I was hoping to get more range of acceptable angle there with a longer draw bar.
Additionally, on somewhat bumpy terrain I often try to get the front wheels of the TV higher than the rear wheels to bring the ball down and help me with the front-to-back leveling of the Scamp, I am am thinking that my ability to employ that variable would be enhanced with a longer draw bar.

On the other hand, as you say, there are serious issues associated with turning, and with torque and tongue forces all through the receiver assembly. I am also concerned that a longer draw bar might increase the chance that the jack foot could hit the ground, when retracted and towing, on uneven terrain, small bridges, etc. (Would you agree with that?)

The order of things on my tongue is: battery (group 27), two tanks, and then the tongue jack. It is entirely the tongue jack that is the issue with blocking the hatch. I am thinking of getter a power tongue jack, which would probably exacerbate my hatch opening issue. (I am reluctant to get an ultimate jack; when I looked into it I believe I recall that they occasionally drop down while towing on bumpy roads? Also, I am kind of looking forward to a simple easy power jack...)
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Old 02-16-2023, 10:20 AM   #12
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Simply measure the weight of your truck's rear axle with your standard receiver/ball. Then hook up the camper and weigh your rear truck axle with the extended receiver/ball. The difference will not be as much as some think.

Enjoy,

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Old 02-16-2023, 11:29 AM   #13
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The Ultimate Jack: I know "somebody said" their's dropped down, I remember reading that, but never had a problem with ours. Just to be safe and eliminate any worry I drilled a hole in the jack foot where I can hook a short chain that is attached to the trailer frame so if the jack does drop it can't hit the road. I also modified the jack so it can be pulled up out of it's base if I want, but never have done so since installing it.
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Old 02-16-2023, 12:30 PM   #14
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Originally Posted by zack sc View Post
It is entirely the tongue jack that is the issue with blocking the hatch.
Manual, but appears to have a low height above the trailer frame.
https://www.etrailer.com/question-141414.html
If the drop distance isn't enough with that low-profile jack, do what many of us do when jack doesn't go down enough: Raise the surface the jack will rest on by stacking leveling blocks.

also manual, but removeable..
https://www.rvupgradestore.com/Jack-...sal-p/5154.htm
Yeah, with that one you'd have to leave the hatch open or leave it closed when the removable jack was mounted, but while hitched there'd be no need to mount the jack. The tongue would still have most of the weight and front stabilizers (or bottle jack?) could be used for that last little lift assist to level the trailer while still hitched.
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Old 02-16-2023, 06:24 PM   #15
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The shorter it is, the better it pulls, the longer it is, the better it pushes. And I'm not trying to be funny.
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Old 02-22-2023, 01:28 PM   #16
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My 1980s Scamp had a swing-away trailer jack. The frame mount allowed it to swing up to horizontal while it was hitched and the support wasn't needed. Seemed like a good idea, and it always worked well. Are those no longer made?
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Old 02-22-2023, 05:23 PM   #17
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My 1980s Scamp had a swing-away trailer jack. The frame mount allowed it to swing up to horizontal while it was hitched and the support wasn't needed. Seemed like a good idea, and it always worked well. Are those no longer made?
They still make them. Trailer Valet even has models with removable handles that come with drill attachments. You could remove the current jack and replace with one of these if there's enough room on the trailer frame.
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Old 02-23-2023, 10:04 PM   #18
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The shorter it is, the better it pulls, the longer it is, the better it pushes. And I'm not trying to be funny.
Interesting point. I think you saying that backing up is better with a longer draw bar. That your rig will be overall more maneuverable going backwards. Is that right? That's interesting. Is that well known?
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Old 02-24-2023, 07:44 AM   #19
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The counter steer (steering wheel to left to make the trailer start right) when backing is equally exaggerated with a longer distance from rear axle to ball as when driving forward. See paragraph 3 in post #9.
At the less-than-walking speed of backing in the site that can be an advantage, but I'll trade hundreds of miles of highway stability for 30 feet of backing during 3 minutes.
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Old 02-25-2023, 08:50 AM   #20
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A longer drawbar does not make it any more maneuverable in normal backing. The tightest backing turn you can make (in a single move) is determined by the turning radius of the tow vehicle. Essentially you can’t turn any sharper when backing than you can going forward because you have to follow it back.

You can, of course, negotiate a tighter turn in close quarters by backing into a jackknife, pulling forward, and repeating several times. A longer drawbar can help with that because it will turn slightly sharper due to the leverage, and the added separation means you might be able to get into a tighter jackknife without making contact. That situation is so rare and the advantages so slight, it isn’t worth the many disadvantages of a longer drawbar.
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