Where does the 10-15% tongue weight rule come from

[Hubert]

So this is a rookie question but why is it exactly....

OK so what is the magic of tongue weight such that 10-15% of trailer is key for a tag along and 25% for a gooseneck/5'er.

Given 2 identical trailers what is it better to err to heavier or lighter tongue weight? When is it too light or heavy?

I can see a minimum weight so to keep traction on rear wheels and trailer won't push tires side ways and the truck will command the trailer tongue. Pickups are invariably front axle heavy unloaded. A diesel longbed is almost like a lawn dart. If air bag equipped or beefy springs the more weight on the rear axle puts the truck more in control doesn't it? (As long as the rear behind the axle hung weight doesn't fulcrum on the rear axle then unload the front axle).

So depending I am thinking really its more leveling and weight split between front axle, drive axle, and trailer axle(s)? So depending on long bed vs short vs overhung distance between rear axle and tongue weight vs tongue length vs tandem vs single axle trailer you can't always just follow the 10-15% tongue weight rule.

I was asked why does more tongue weight help towing control. And I thought well on a leaf spring setup it squats the leaf spring pack together and they get stiffer and bind together better to get more rigid. When a pickup is unloaed the top springs are what controls the rear axle. The lower springs aren't really doing anything.

Then whats after that I would guess is load balance.

[DickWells]

Well, let me add my .02 with a + for experience. My former trailer grossed 5500lbs when new, and I towed with my 95 Suburban 2500 -4x4. I used a dual cam hitch with 600 lb bars, and was always very pleased with the handling. I had just about 400 lbs of actual tongue weight at the time. Later, I got a Bombardier Traxter for(OUR) 42nd anniversary, and needed to take it with me wherever I went. It weighs over 850 lbs. Soooooo, I laid out a new tongue extension on the floor of the garage, and welded and bolted it up to add 39 inches to the tongue. In the process, I gained enough room to drive the 48 inch wide Traxter on crossways. I reinforsed the frame all the way back to the spring mounts of the trailer, too. In all, I added 360 lbs of steel to the trailer. Ended up with 1420 actual pounds of toungue weight! I changed to 1200 lb dual-cam bars. I got a trailer that handled even better! I towed it from VT to OR with the stock rear suspension on the Burb. Added Firestone bags while in OR. Went on to tow that trailer/ATV something like 40K more miles before I traded trucks and trailers. BTW, I made a new cross-member to put a 2 5/16" ball under the old socket, and bolted everthing on with grade 8 bolts, so the the old trailer could be brought back to stock.
Ten to 15%? I had ~19.7 % for 40K miles, and never felt insecure. I always thought that without that added tongue length, I would have had a bear by the tail. Of course Sun Line and GM would have had a fit.
Also, I firmly believe that the dual-cam hitch had a lot to do with it. Most of the dealers will tell you that a dual-cam is a waste of money with a light travel trailer, but I always enjoyed having those cams hold me straight when passing or being passed by semis, or in cross winds. Load leveling chains won't do that for you.
Transfering the proper weight to the front of your horse is important, too. I keep a lot of weight levered forward when towing. The only time I take some weight off is if I hit snow on the road. Don't like it when the front tires wash out on me! BTW, I used to have close to a ton of weight in and on the Burb, besides the trailer behind.
A long winded way of saying that I'd go for the heavier tongue every time.
If you see the rear of your trailer swaying back and forth in your mirrors, you can almost bet that you can eliminate it by getting back there and carrying some of that stuff up front.
Have a good day.
Dick Wells:)

[DennisG01]

I'll just add another "from experience" comment. Now, this comes from towing boats, where the general rule of thumb is 7 - 10%. Why the difference? I don't know. But I can also tell right away if there isn't enough tongue weight. Always err on the heavier side for tongue weight. Too little tongue weight will equal swaying. Hopefully you figure this out before it starts to happen - and swaying typically won't start to happen until you get to highway speeds. One thing I'll do when pulling an unfamiliar rig to "feel it out" is do some quick jerks on the steering wheel to see how long it takes the trailer to come back in line with the truck. It should come right back within one or two "sways". Obviously, start with smaller jerks at lower speeds.

However, to answer your original question of why? Honestly, I don't know. But it works. My guess would be some group played around, doing maneuvers like I described above until they came up with a "standard". Just a guess.

Too much tongue weight can obviously cause the vehicle to squat - possibly having the rear suspension ride on the bump stops. The more it squats, the more it screws up your headlight alignment, as well - among other things, blinding other drivers. Too much squating will also take too much weight off the front end causing dangerous handling.

When I was about 16, I towed a boat with a Chevy Luv. I got up on the highway and all of a sudden realized I was turning the steering wheel and the truck wasn't responding - I vividly remember turning it completely lock to lock!!! The front wheels were off the ground! Luckily, I brought it back to center, eased off the gas and it settled back down. I pulled over, parked, hopped over the guardrail and walked to a nearby restaurant where I called for a bigger truck.

[DickWells]

We saw a really horrible wreck, down in NC back in 98. Guy was trailering an S10 on a little flat bed, behind a Ford Ranger! Probably would have gotten away with it, except that he was going too fast and whipped out to pass a truck (Southbound), and lost it. Came across the median and rammed head-on into a cab-over semi Northbound. It was a sleeper. The guy in the bed got out alive, but both drivers died! This was going up a rise where 95 went over a secondary road. We were stopped for almost 4 hours. We saw the semi engine/trans come by us on a wrecker boom. Then what was left of the cab. Never did see a piece of the two compact pickups that were ricognizable. What a terrible waste. Some fool puts a bigger weight than his horse behind him on a utility trailer with no brakes and expects to go the speed limit! Drivers that he had passed were livid! Not much could be done to a dead man, though. His front tires weren't responding, either.
Got a nice, exciting ride with my Dad back in 56. The WB was 156" on his Ford 1.5 ton. We added dollies behind and 4' to the flat-bed. However, the dollies were locked in the up position for traction in the snow. Thing is, we had a full load of 16' logs on. Hit the first pot hole going down hill, and those loooong logs just levered the cab right up in the air about 6' before he could start bringing it back down with the rear brakes! Steering wasn't worth beans! I wasn't pleased with that floating sensation, either! I was 16 at the time, and full of P & Vinigar, but it got exciting for a few seconds. He got it stopped, put the dollies down and put chains on till we hit pavement. Don't recall that it ever happened again, to either of us.
Just another old war story. Thanks for listening. If you did.
Dick Wells:)

[MacDR50]

A heavy tongue, more than the suspension was designed to handle will tend to wag the tail of the TV. It forces the balance of the truck closer to the hitch point. The effect is felt in steering control and increased sway. In a panic stop where the trailer is not perfectly inline with the truck the tendency of the trailer to push the trucks rear sideways is greater. We had a near tragic accident with a 2500 pulling a double axle flat bed trailer with a load that was too far forward. The driver hit a dip in the road with one side of the trailer and it pushed his rear end into the guard rail. He took out $3000 worth of rail. The drop on the other side was 30+feet almost vertical into a boulder strewn ditch. Too light a tongue weight I am not so sure but it may be the pendulum effect of the trailer is increased due to the trailer balance being shifted further back toward the rear axles. I did a quick search and this little treatise is as good as any I was able to find.

http://www.etrailer.com/faq_trailertowtips.aspx

My 5th wheel has a PIN of about 17-18% due to its design. I haven't towed it with the new truck yet so I have no idea what that will mean in terms of handling. In a dually it felt good but then that is to be expected with four tires on the road resisting any imparted sway.

[DickWells]

Sitting in a diner ounce in Huntsville, AL, and heard a terrific screeching of tires. Looked out on the street and a guy in a Ford was trying to stop at the red light with a HUGE, LOOOONG power pole strapped to an axle at about the mid-point. The front of the Ford was bouncing up and down and ducking left-right, almost too fast for the driver to react with steering input! Talk about exciting! He went right through the intersection, and 3/4 the length of the pole, and sat kitty-cornered in the street. He sat there long enough to compose himself, and then crept away real slow. Bet he waited to be alone, before he climbed out and exposed his trousers to the World!:D
I bought a light utility trailer (6' X 8') back a few years, and towed it about 100 miles home with the Suburban. This trailer weighed about 400 lbs, but would duck left-right so fast that the little 12" tires would slide if you went over 45 mph. Thing is, it was perfectly balanced F-R, with a short tongue. I stopped and loaded about 100 lbs of stone into the front, and cured the sway. When I rebuilt the trailer, I added two feet to the tongue and moved the axle back to get 2/3 of the bed in front. A great handling trailer, now. Even has a Mossberg 12 ga. shotgun receiver and bolt in front to lock the tilting bed down! It's gold-plated, too, cuz it almost cost me a hand, due to Stupid Here using a big right-angle grinder like it was never ment to be used! Arg! STUPID! Still have a numb left pinky to show for that one! Sorry about the "more info than you signed up for", folks.:o
Dick (Graceful!) Wells:):o

[Hubert]

Thanks for the comments. Well, I am thinking the 10-15% is just a generic rule of thumb. And only that. But due to commonality ? of most people's trucks and loads it works ok most of the time.

To really compare loading and balance you would have to know trailer length, wheel bases, center of gravities and axle to hitch then to trailer axle distances. I'll have to sit down and see what the ratio of wheel base and axle to hitch point is for my truck and a couple of avg trucks to see the numbers.

My truck empty weights approx. 4000 lbs front and 2000 lbs rear axle thats a lot of bias and would have to have a pretty big tongue weight to lift the front tires. But would think could easily be too light and loose traction on rear wheels in a turn if trailer was heavy and pushing sideways on the hitch with just 10% tongue weight.

For a 5'er as long as the pin point is in front of the rear axle appreciably I would think the heavier the better (within reason and consideration for suspension strength).

[Mark Rinker]

That is a good rule of thumb, however there are lots of variables introduced by the trailer and its loaded weight, the truck's rear suspension/tire capacities/hitch, etc. Whats nice is a load that can be moved, like hauling a car or Bobcat. Drive it on, pull forward until you see the truck start to sag, back up a bit, chain it down. I suspect the positioning of personal effects, freshwater/greywater load inside a 5er would be a similar, dynamic variable to be considered.

Whats a PITA is setting a boat with a crane operator at $150/hr and making the call once - and living with that 'set' all the way to Florida...read my other thread.

Bottom line is you get a feel for it. You can 'see' the right set, as its happening.

Don't ever hit the road if you know its wrong.
Don't ever tow without enough brakes to stop your load safely
Decrease speeds for towing.
Get off the road in inclimate weather. Change your plans.