My wife and I are looking very seriously at selling/trading our very small travel trailer for something much larger. I have the weight considerations figured out per safety concerns but have not had much luck at finding out what length I should be shopping for with safety in mind. Anyone w/ info about this, I would certainly welcome hearing from.

 

Found the answer to my question...
Overall trailer length, front cowling to rear bumper, "Rule-Of-Thumb":
20’ trailer for the first 110” of wheelbase plus one additional foot for every 4” of wheelbase thereafter provided the manufacture’s Combined Gross Vehicle Weight Rating and Tongue Weight Rating isn’t exceeded.

 

That is an interesting rule of thumb. I wonder how semi trucks calculate how much trailer they can pull, lol While Im sure the math probably works out close, the bigger concern is probably actual tonque/trailer weight than specific length of the trailer. If you had a 24' aluminum frame trailer that weighed the same as a 20' steel frame, they probably tow the same regardless of their length compared to the wheelbase. This is me just thinking out loud though. . .

 

If I'm not mistaken, the above formula mentions both. CGVWR and TWR which has a formula of its own for computing safety margins. That's why I started w/ CGVWR and worked backwards with known weights to compute a DGVWR. Since length and sway go hand-in-hand, which can be controlled w/ various types of sway control systems for various amounts of $, a recommended maximum length safety wise was what I was looking for.

 

I see. I agree with you on the known weights, I was just surprised to see length come into play as opposed to just GTW. Most people just try to get the most length they can for the weight, with little regard as to the length in general. That's why I mentioned that most probably wouldn't care whether it was a 20ft or 24+ft trailer; as long as the GTW is within specs for the truck people will choose the longest trailer they can get, price and features notwithstanding.

 

I think I would be more concerned about the tongue weight, gross trailer weight loaded, and location of the trailers water and holding tanks than any formula. I can tell you from experience that if the trailer's weight center is primarily over or before the axle(s), and you have about 12 to 15% of the weight on the tongue, your trailer will tow fine. The more the weight is toward the front rather than the rear of the trailer, the better the trailer will tow. Also, a weight distributing hitch is a godsend when towing travel trailers.

As for the wheelbase of the tow vehicle, the one time that would be a consideration would be in manuvering the vehicle, especially in backing. The longer the wheelbase of the tow vehicle, the slower to respond to driver adjustments to correct the trailer while backing. That is one of the reasons why the 'yard goat' at many large warehouses that moves semi trailers to and from the dock is a very short wheelbased vehicle. The other time it might be a consideration is in vehicle ride comfort. A longer wheelbase vehicle will generally ride more comfortably than a shorter wheelbase vehicle whether loaded down or not.

Personally, I would rather have the shortest vehicle wheelbase within reason, along with a trailer that has its freshwater and graywater holding tanks, as well as outside access storage, toward the front of the trailer and ahead of the axle(s). I know that the tow vehicle will ride a little rougher than a longer wheelbased tow vehicle, but I would rather have the manuverability and shorter total length. And with the trailer's load more toward the front, the trailer will have less chance of swaying down the road.

 

According to that rule of thumb I would be over it with my 30ft travel trailer being pulled by my 139" wheelbase screw. My trailer is an ultralight and dry weight is around 6300# I believe? I have never felt like I was overloaded with it and it pulls like it is barely there. Good tires, a good trailer brake and sway control do wonders when towing. That being said I don't think I would go any longer than 30ft. I have a tractor that I pull on a 18 ft trailer. Actual weight is probably more and I am not near is comfortable with it as I am the travel trailer.

 

I appreciate the feedback and, as always, provided interesting reading. I agree with some of the remarks and strongly disagree with others.

Since I’m known to “over research” a purchase I’m also known to be a safety freak! That was the bases of my question. Length NOT weight. My known weight calculations (see pic. at the start of this thread) determined the maximum DRY weight of a travel trailer my F-150 can pull being 6,810 lbs.

In “over researching” by both internet and RV shows I have discovered this:
Thousands of TTs out there that fall well within the weight limitation. Eliminating all but 3 floor plans, that number got reduced to hundreds. Eliminating out-of-balance TTs based on tongue weight/dry gross vehicle weight equaling not less the 10-15%, indicating a trailer not engineered correctly with safety in mind, leaving about a dozen or so TTs, bringing forth the question of length.

High end $ TTs tend to weigh more then low end $ TTs per foot. Low end $ TTs tend to offer more options then high end $ TTs per foot (base price). High end $ TTs tend to be shorter, 25’ -29’ then low end $ TTs at 27’-32’ with a few at 34‘.

Since the cost factor from high end to low end TTs can be as much as $5k to $8k the remaining unknown factor, to me at least, was length vers safety.

The purchase of my F-150 was by design not by accident, special ordering it indicates that. After giving considerations for its usage, that being towing and showing (which has already paid for performance mods.), choosing cab type, 2 or 4 wheel drive, gearing, and of course unnecessary options, ended up dictating the SuperCab XLT 4x2 with a 5 ˝’ bed.