The 80% tow rule. Where did it come from?

[Gene]

Originally Posted by flmgrip

because we are split between the one side saying big is bad and the other side saying big is good with no resolution is sight...

Discussion here isn't dependent on counting up sides. We make a point, some agree, some don't, some change their minds, others just read it and quietly make up their minds. At some point everything to say is said, and the thread dies, maybe to be resurrected some time later.

There will not be total agreement on just about anything including a thread called "Do Airstreams Look Good?"

I think it's an interesting question and one I wondered about before purman posted the original question. The larger question surrounding it is about conventional wisdom.

Gene

[hampstead38]

Returning the subject, I don't know that anyone can say where exactly the 80/20 rule began. It's not an 82.17 percent rule or a 78.65 percent rule. My guess is that someone said, "If the manufacturer says 10,000 pounds... I'm going to take 20 percent off 'just to be on the safe side.'" And someone else said, "Yeah, that sounds about right." Add water, stir briskly... boom, you have "rule."

I'm the first to admit my wife is a much driver than me. She can shame NYC cab drivers with her moves. On unpaved roads, snow, rain or towing, I'm a better than average driver because of my experience and caution. In heavy, or even routine traffic, I'm a worse than average driver. I just don't have the patience or urban instincts for the work.

Unlike many drivers, I know about how vehicles work mechanically. I think about things like brake fade. I understand compression braking. I know when something sounds or feels "not quite right." I actually install gauges (rather than idiot lights) and even look at them. I do a "walk around" before pulling out with the trailer hitched up. Everything gets checked.

This isn't going to save my backside if some idiots cuts me off or runs into me. Neither is a one-truck truck. The simple fact of the matter is that the vast majority of auto accidents are caused by driver failure... not mechanical failure. Booze kills more people than bad brakes. Distractions like cell phones, make up, eating, radio fiddling, etc., kill more people than a smaller horsepower engine. Running a vehicle at its legally rated capacity probably wears it out faster. It probably means going up hills slower... and hopefully down them slowly as well. It means having to drive more carefully and cautiously. I simply don't think shaving 20 percent off the rated capacity changes the towing dynamics of a safely operated vehicle towing a legal load to the point where it makes a statistically significant difference in avoiding or surviving accidents.

[Action]

Originally Posted by mutcth

I guess what troubles me most about this thread is that, given a list of accidents, one really doesn't know if a different tow vehicle would have prevented it. (Maybe weight distribution wasn't used. Maybe the sway control wasn't set correctly.)

Tom

Throwing my 2 cents in .....

I believe there are 3 factors.
The driver and his or her skill
The equipment that is going to be used
And how that equipment is set up and maintained

Seeing a graphic video is eye grabbing, however to make a stement as to why the accident occurred based on the vid is to make a decision with out all of the parts and pieces. For all we know the drive may have been reading a map and did not have his full attention on the road.

I personally have a decaded daily driver that is used for that purpose. If one is using (or buying) one vehicle to do a daily commute and tow a 5000 # + load, then think of all the money you saved by not buying (or having) a second vehicle. In my opinion you will need to pony up to a vehicle that will handle the largest load expected. And if that means the MPG is poor. Well consider the $5,000 to $20,000 you saved in not having the 2nd vehicle. RVing isn't necessarily cheap.

As to load capacity - I do not exceed the rated capacity of my TV. However I am way over 80% of the rating. I am also the guy driving at or 5 mph below the speed limit getting nasti-grams from the dude that wants to fly by at 5 to 15 over the limit. I expect my equipment to handle the load the manufacture states, and set up the TV and trailer to travel level. I also maintain everything better than the schedule. And never drive with liquids if at all possible.

Just my opinion

>>>>>>>>>>>>>>>>Action

[mutcth]

Originally Posted by flmgrip

the 3000lb car pulling a 7000lb trailer is stopping faster than a 7000lb truck pulling a 7000lb ? i would like to see that....

Comparing 1/2-ton trucks to 3/4-ton trucks, the 1/2-tons typically have shorter stopping distances. Same goes for the typical car-based, 5000lb SUV vs a 5500lb truck-based model. Stuff like tires and suspension weight transfer when braking play a role, not just big impressive looking rotors and calipers.

Although your example is obviously extreme, stopping 10000 lbs of mass is easier than stopping 14000 lbs. A F-250 weighs nearly 2500 lbs more than a F-150, which doesn't help matters.

Properly adjusted trailer brakes are, of course, a help here - old Airstream brochures I have brag that the tow car + disc-braked trailer stopped in the same distance as the tow car (a 3500lb late-70s Chevy Impala) did solo.

There are so many variables here beyond tow rating: we passed a SOB (which is a lot higher than a typical AS) being towed by a newer Silverado 1/2-ton recently. No sway control, no weight distribution - it was wagging down the road, nose in the air, even at the speed limit. That rig was likely 2000 lb or so below the tow rating of the truck, yet was inherently less stable than my minivan towing my Minuet with weight distribution and anti-sway.

Tom

[dkottum]

Good arguments on both sides. A frequent poster with years of Airstream repair experience states that anything over 1/2 ton is very hard on your trailer. That's an important consideration. Perhaps the 80-20 rule has had it's day, and modern hitches, engine/transmissions, brakes, and active suspensions are making the old rule unnecessary. Do we really care if someone passes us going up (or down) a hill, if we are driving safely?

[Action]

Originally Posted by dkottum

A frequent poster with years of Airstream repair experience states that anything over 1/2 ton is very hard on your trailer.

That isn't a universal statement. Even that person would say so. There is a big difference between a Bambi and a 34 footer. Using a 1/2 ton in front of a 34 footer may be hard on the TV and trailer.

>>>>>>>>>>>Action

[16595]

In looking at the front wheels of that Excursion closely - I would say that any vehicle would handle about the same. The driver's reactions are slow and the vehicle is just following (what appears to me to be) ill-advised inputs. Several years ago I had a good whip on my 99 suburban (half ton) and an '86 31' airstream. But I steered the vehicle in a straight path down the interstate, used trailer brakes and then canceled the cruise. It was a bit harrowing, but everything settled down nicely. The whip was generated by a good wind from the left, a box-van truck in the passing lane, and a light duty tow vehicle.

The driver of the Excursion is not steering straight or close to it. I don't feel you can blame the vehicle in this case.

Ooops. Post #70

Dwight

[flmgrip]

Originally Posted by CrawfordGene

Discussion here isn't dependent on counting up sides. We make a point, some agree, some don't, some change their minds, others just read it and quietly make up their minds. At some point everything to say is said, and the thread dies, maybe to be resurrected some time later.

There will not be total agreement on just about anything including a thread called "Do Airstreams Look Good?"

I think it's an interesting question and one I wondered about before purman posted the original question. The larger question surrounding it is about conventional wisdom.

Gene

well said and I stand corrected

[flmgrip]

I understand what you are saying and you are correct too to a certain point, but if your trailer wheights twice as much than your TV you will be in trouble earlier than a TV that's better 'matched' with your trailer... That's just physics...

Anyone living in the great L.A. area knows the 'grapevine'... Do you know how much brakes I use going down that thing? zero... My TV is braking my trailer perfectly and I am going 58mph. My brakes are cool and not smoking, now if there is an emergency my 14000lb rig will stop before yours at 10000lb... And even better, if my trailer brakes fail I still can stop this beast...

Originally Posted by mutcth

Comparing 1/2-ton trucks to 3/4-ton trucks, the 1/2-tons typically have shorter stopping distances. Same goes for the typical car-based, 5000lb SUV vs a 5500lb truck-based model. Stuff like tires and suspension weight transfer when braking play a role, not just big impressive looking rotors and calipers.

Although your example is obviously extreme, stopping 10000 lbs of mass is easier than stopping 14000 lbs. A F-250 weighs nearly 2500 lbs more than a F-150, which doesn't help matters.

Properly adjusted trailer brakes are, of course, a help here - old Airstream brochures I have brag that the tow car + disc-braked trailer stopped in the same distance as the tow car (a 3500lb late-70s Chevy Impala) did solo.

There are so many variables here beyond tow rating: we passed a SOB (which is a lot higher than a typical AS) being towed by a newer Silverado 1/2-ton recently. No sway control, no weight distribution - it was wagging down the road, nose in the air, even at the speed limit. That rig was likely 2000 lb or so below the tow rating of the truck, yet was inherently less stable than my minivan towing my Minuet with weight distribution and anti-sway.

Tom

[Diesel1]

Originally Posted by flmgrip

I understand what you are saying and you are correct too to a certain point, but if your trailer wheights twice as much than your TV you will be in trouble earlier than a TV that's better 'matched' with your trailer... That's just physics...

I don't think overkill in and of itself is a bad thing. But I also understand why Inland Andy sayes heavy TV are hard on Airstreams. I pull my 1967 Tradewind with a 1994 1/2 F350 4x4 SRW 7.3 diesel. It is the heavest sprung truck I have ever owned, it is a bit uncomfortable to drive. But I owned it when I got the Airstream, didn't make much sense to change. So I ajust every thing from tire PSI to towing speeds to keep from beating my trailer. That being said I don't think I "need" that much truck( altho it is very stable).
I also pull a semi load of potates from Idaho to Phoenix every couple of weeks. The tracter weighs about 25,000 pounds, the loaded trailer about 55,000 pounds. Thats a bit over two to one weight. I cross numerous 6% grades and one ten mile 8% grade.Never do I feel unsafe or out of control. I pick the appropiate gear, turn on the Jakes and enjoy the ride down.
My point is if the rig is loaded and balanced properly and the braking system is doing its intended job the TV does not need to be bigger than the trailer to be safe. Adios, John

[47WeeWind]

Originally Posted by Diesel1

I also pull a semi load of potates from Idaho to Phoenix every couple of weeks. The tracter weighs about 25,000 pounds, the loaded trailer about 55,000 pounds. Thats a bit over two to one weight. I cross numerous 6% grades and one ten mile 8% grade.Never do I feel unsafe or out of control. I pick the appropiate gear, turn on the Jakes and enjoy the ride down. My point is if the rig is loaded and balanced properly and the braking system is doing its intended job the TV does not need to be bigger than the trailer to be safe. Adios, John

Hi John:

Like you, I too believe some overkill is a good thing. But I bet you'd have a much more "exciting" (or perhaps slower) ride from Idaho to Phoenix if your 55,000 lb. semi-trailer was attached to your 25,000 lb. tractor with a rear end pintle hitch instead of a fifth wheel. A fifth wheel hitch mounted slightly forward of the center of the (tandem) rear axle(s) is inherently more stable than a "bumper pull" or rear end hitch as used on most travel trailers. A fifth wheel tractor should be able to tow more weight more safely than a tractor (or tow vehicle) having a rear end mounted hitch. I appreciate your experience, but believe you are comparing apples to potatoes.

[Diesel1]

Originally Posted by 47WeeWind

Hi John:

Like you, I too believe some overkill is a good thing. But I bet you'd have a much more "exciting" (or perhaps slower) ride from Idaho to Phoenix if your 55,000 lb. semi-trailer was attached to your 25,000 lb. tractor with a rear end pintle hitch instead of a fifth wheel. A fifth wheel hitch mounted slightly forward of the center of the (tandem) rear axle(s) is inherently more stable than a "bumper pull" or rear end hitch as used on most travel trailers. A fifth wheel tractor should be able to tow more weight more safely than a tractor (or tow vehicle) having a rear end mounted hitch. I appreciate your experience, but believe you are comparing apples to potatoes.

Morning Fred, (I feel like the two sheep dogs at the time clock on the old Looney Tunes cartoon) You made me laugh with the potato to apple thing. And you are very correct, that is why I ended my remarks with properly balanced, brakes...etc etc. If I did not scale my load and could run illeagally I could put a lot of the load on my trailer axles( potatoes are HEAVY) which would unload the drivers on the tracter causing physic's to take over in all sorts of unhappy ways. But since I am required by law to drive over scales at frequant intervals my load is balanced which mantains the inherant stability of which you speak. My point is you do not need the tow vehicle to outweigh the trailer even with a bumper pull. But you do need to know what your trailer weighs and what your tongue weight is. After that it is simple there are formula's that tell you how to arrive at proper tongue weight's, and do not exceed the GVW of the TV.Make sure the trailer brakes function as intended. Adios, John