Downside to tongue weight over 15%?

69 Avion wrote:
I carry a quad on the trailer (along with one in the truck) and I have a couple of generators, so the gasoline with it's electronic fuel pump and dispensing hose comes in real handy. Actually, the generator gets very little use since I added solar. I still need it in the summer, when I run the AC.

Thanks.

myredracer wrote:
I just came across this interesting article yesterday on another thread. How to tow safely
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The author also discusses "back of ball" ratio, or "BOB" for short which I've never heard discussed before. He says that the axles should be 70-80% towards the rear from the overall length ball to bumper for optimal towing stability. I'm not sure how well that would work in the more recent designs of trailers that can heavy components, like say slides, biasing weight more wt. to the front or rear and what it would do to tongue wt.

When looking at possible new trailers, I calculated the BOB whenever I could get the measurements. My old trailer was 76%, with the axle set pretty far back, and very stable towing. Most trailers we looked at were a lot lower, many in the 60's, a few in the 50's. Our new trailer is about 75 and it too is a very stable tow.

But a hihg BOB probably also means a high tongue weight. Both our trailers are a bit over 15% which must also contribute to stable towing.

myredracer wrote:
I just came across this interesting article yesterday on another thread. How to tow safely

The author talks about a "standard" 8-12% tongue weight. It appears that the article is rather dated though.
...

He's trying to compensate for low payload in the tow vehicle.

The reasons for the 8-12% hitch weight are 1) the limitations of fixed-ball weight-
distributing hitches and 2) the load-carrying capacities of the average towing vehicle.
Although a 15% hitch weight on a 30-foot trailer coach (about 1,200 pounds) may work
for your towing vehicle, for most vehicles and hitches it would be too much. Thus, the
need for this 8-12% standard.

Think he would agree that it's better to go with a higher % hitch weight *and* a vehicle that can support it. But he doesn't get into it much. Payload limitations of the time I guess.

I just came across this interesting article yesterday on another thread. How to tow safely

The author talks about a "standard" 8-12% tongue weight. It appears that the article is rather dated though.

The author also discusses "back of ball" ratio, or "BOB" for short which I've never heard discussed before. He says that the axles should be 70-80% towards the rear from the overall length ball to bumper for optimal towing stability. I'm not sure how well that would work in the more recent designs of trailers that can heavy components, like say slides, biasing weight more wt. to the front or rear and what it would do to tongue wt.

wmoses wrote:

69 Avion wrote:
When I built my last camping trailer I put the extra water (34 gallons) right in front of the axle and the gasoline (20 gallons right in front of that. The reason is that water is 8.33# per gallon whereas gasoline is just over 6# per gallon.

What was the gasoline for?

If I had to guess it would be for an onboard generator.

Back to the longer tongue... We were huge into boating years ago, and powerboats on trailers towed well with between 8-10% TW because the center of mass was usually near the back where the motor is and that placed the wheels far back to get the TW up. Sailboats were more like RV mostly because they had a weighted keel midship, so the axles were more to the middle of the trailer.

What would be nice I think is if they made a rear bedroom TT with a big trunk behind the bed. You could still have the typical one up front, but if you could load up the rear with stuff and have the axles shifted back to compensate I think it might make for a decent tow for a lighter-weight TV. Sure the unloaded TT would have a higher TW, but no one really tows it like that anyway.

wmoses wrote:

69 Avion wrote:
When I built my last camping trailer I put the extra water (34 gallons) right in front of the axle and the gasoline (20 gallons right in front of that. The reason is that water is 8.33# per gallon whereas gasoline is just over 6# per gallon.

What was the gasoline for?

I carry a quad on the trailer (along with one in the truck) and I have a couple of generators, so the gasoline with it's electronic fuel pump and dispensing hose comes in real handy. Actually, the generator gets very little use since I added solar. I still need it in the summer, when I run the AC.

69 Avion wrote:
When I built my last camping trailer I put the extra water (34 gallons) right in front of the axle and the gasoline (20 gallons right in front of that. The reason is that water is 8.33# per gallon whereas gasoline is just over 6# per gallon.

What was the gasoline for?

The issue of a longer tongue helping with stability is correct. The longer the tongue the better the handling in most cases. The placement of the axles creates the same stability. You actually don't need a longer tongue if you just move the axle back to give a longer length between the coupler and the axle. It does appear that many manufacturers like to keep that distance at a minimum to keep the tongue weight lighter which is important if you are trying to tow with a lower rated vehicle. TT manufacturers need to spend more time placing all tanks closer the axles and slightly in front if possible.
When I built my last camping trailer I put the extra water (34 gallons) right in front of the axle and the gasoline (20 gallons right in front of that. The reason is that water is 8.33# per gallon whereas gasoline is just over 6# per gallon. The placement of the loads in the trailer, especially the loads that vary (tanks etc) is critical to a trailer that tows well. Having the heavy loads as low as possible is also very important. This particular trailer has much of the weight between the frame rails, under the camper so that it has as low of CG as possible while still maintaining decent ground clearance.

Ron Gratz wrote:

myredracer wrote:
Everyone out there says your tongue weight should be between 10% and 15%, but exactly why the 15%?

The upper limit of 15% originated with tests conducted in 1979 using subcompact, compact, and intermediate cars as tow vehicles.

If the tests were done today with modern tow vehicles, the numbers probably would be different.

Ron

I'll add some to what Ron has posted.

First off, Ron being "King of the best links!" :C Linked us to this site a while ago. http://www.edccorp.com/library/techref.html

Some of us as are as curious as others... (not mentioning any names) follow those links and read them too.

Back in 1979 NHTSA hired EDC an engineering firm to study towing dynamics related to autos having towing accidents of the time. If you scroll down that link, there are 4 volumes under the Library Ref number on the left. # 1081, 1082, 1083 and 1084 related to car and trailer handling and braking studies. If you print them all out, it creates a stack of paper 1" thick printed on one side. Ask me how I know....

Here back in 1979 a lot of the same things we are up against today where talked about back then. Some came to be common place, others seems to be mothballed. Like the recommendation that the TV mass be larger than the trailer. H'mm, a study done and recommended that?

The topic of tongue weight came up too and there was even calculations concerning the length of the trailer tongue on how it affects trailer towing stability. By lengthening the trailer tongue extension, less weight is needed to be held by the TV to have the same stability as it's shorter standard A frame setup.

For example, the standard A frame has a 50 deg inclusive angle and the majority of our TT's are setup on this 50 deg tongue that has an extension of approx 32 to 40" from the face of the TT body. And now the V noses are even closer to the ball. There is not an exact set standard on how close the TT end cap is to the ball, however the 50 degree A frame with the ball coupler at the end seems to be the way to build a camper.

If the trailer front end cap stayed the same length from the TT axles, however the ball coupler was extended for example, 4 feet more, an increase in towing stability would occur and less TW need to be held by the TV. This may look a little "different" and it backs up more like a PullRite hitch, however it is a very passive way to get out of the 10 to 15% TW range. Do not know exactly why this principle didn't take off, maybe too radical a thinking, costs more for the steel to make the frame, camp site length issues or there was some other towing dynamics that did not come up in that report.

Since the industry seems to be stuck on building trailers with the shortest possible A frame and ball coupler distance from the main mass of the trailer, 10 to 15% will most likely be here for a while.

My prior camper started out with a 14.5% dry tongue weight. When I loaded it and was still ~ 800 lb short from being at GVWR, I was over 20% TW per GVW.

The current camper I have now, has a 16% loaded TW and that is after I rebalanced it to get more storage space aft of the TT axles. It would of been in the 18% range if I had not.

Floor plan, TT axles location and where you can load camping gear drives the TW from where the TT dry weight starts from. In my case both of my campers have been rear living area campers. That nice big picture window and 2 swivel rockers in the back do not do much to offset all the cargo storage space upfront so the TW rises quickly. Some brands are now changing the axle position because of this high weight rise to mate up with smaller TV's on this floor plan.

As was said the truck has to be able to handle a 15% or higher loaded TW. And as was also found in some cases, the TT A frame has to be heavy enough to not fail under 15% loaded TW from a WD hitch.

Other than the Jayco special ultralight weight TT frame of years back, and the Forest River Back Packer TT series, those are the only TT's I have seen with a rating sticker not to exceed 1,000# loaded TW. Never talked about TW %, only loaded TW.

Air Stream may have some kind of rating. I declare I have not seen that many Air Streams however read of the concerns of heavy spring trucks when towing them in some cases can cause problems with the A frame.

Does anyone here on this post know what your A frame is rated for when using a WD hitch? Anyone? Have you seen it as a rating in writing from the manufacture? Can it handle 15% TW with a WD hitch?

John

eluwak wrote:
Our TT was too light in the tongue, and I had to move a bunch of stuff around to make it heavier. Moved the spare tire to the front compartment, and added a heavier ladder there. I even thought about getting cinder blocks to mount on the tongue. We always tow the trailer with empty tanks since the waste is in the rear.

If I had a truck that could handle 15%+ I wouldn't be concerned about it... It seemed like the heavier the tongue got, the better it towed.

Someone else gets it. Congratulations.......