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Old 06-13-2016, 11:11 AM   #51
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Originally Posted by B and B View Post
75 mph is 10 mph over most tire ratings. Do you have some of those new ST tires that have the extra rating?
I'm not sure how new they are but yes, they are stamped on the side with 75mph max speed.

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Old 06-13-2016, 07:14 PM   #52
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Originally Posted by nrkmann View Post

p.s. Why are you hooked up to tow with the TV antenna up? That should be part of your pre-tow checklist. Before we move an inch we have two to four walk arounds and interior checks. My wife and I always see things that the other missed. It just make you safer, the trip easier, and cheaper.
I'm not sure if you were referring to me about the TV antenna, but as far as I know, my antenna doesn't move extend or retract.

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Old 06-20-2016, 10:51 PM   #53
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Just curious how the by the book, engineers need to be 100% trusted, the letter of the law towing guide needs to be followed, crowd get past the Ford F150-F450 60 sq ft frontal area limit for bumper pulled trailers? The trailer the OP posted about is at least 72 sq ft, and I bet most of the 5ers around here are over the 75 sq ft limit as well for those. I agree engineers need to be trusted but I don't believe engineers are the only folk involved in what number Ford puts out.
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Old 06-21-2016, 09:04 AM   #54
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Originally Posted by Hersbird View Post
Just curious how the by the book, engineers need to be 100% trusted, the letter of the law towing guide needs to be followed, crowd get past the Ford F150-F450 60 sq ft frontal area limit for bumper pulled trailers? The trailer the OP posted about is at least 72 sq ft, and I bet most of the 5ers around here are over the 75 sq ft limit as well for those. I agree engineers need to be trusted but I don't believe engineers are the only folk involved in what number Ford puts out.
I'm an engineer for one of the biggest defense contractors in the world. We build stuff with limits or "do not exceed" for a reason. Why? Because people will die if it's not used as intended, expected, or beyond limitations. We've tested it and engineered safety margins in to it. We know that the safety margin drops dramatically if you go beyond a certain point. The laws of physics cannot be broken casually like a 55 mph speed limit! They are real and when you try to mess with them, the wheels fall off quicker than a Chinese motorcycle.

I'm not familiar with those frontal area numbers, but I would imagine it has to do with wind load at speed. Does it mean from frame rails upward to where the front starts sloping back? Or is it from the top of the tailgate of the tow vehicle to top of the trailer since this is realistically where most forces are applied? If you go with full frontal, that's probably 8 x 8 ish and at the 60sq ft mark. I would imagine most travel trailers would fall into this limit these days given the sloped fronts, etc.

As far as the forces applied, think of it this way. Ever carry a piece of sheetrock or plywood? I can carry 2 sheets at a time. And then on days with a breeze, carrying one sheet is an adventure! If its a 12 foot piece, you better get 2 people. My point is that the slightest amount of wind load influences a flat surface more than you can imagine.

Same goes for the frontal area of the trailer. Get it up to 60mph and that is a LOT of wind load pushing on the tongue and influencing the back end of the tow vehicle. Have too big a "sail" area and you end up with the tail wagging the dog. When you increase the frontal size, you increase the forces exponentially and you can go fast enough where that force is exceeding the influence the tow vehicle has to keep the trailer on track.

In the end, physics and the math behind it are constants since the days Newton put them to paper. Calling BS, ignoring them, or using "gut feeling" does not make them go away. If the manufacturer says "don't do this", as an engineer I would tend to agree.

I respectively say, do what YOU think is best for YOU and YOUR equipment. Safe travels everyone!
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Old 06-21-2016, 09:35 AM   #55
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The frontal area deal in ford's towing guide confused me when I was looking at a Ford. It says

Frontal
area
is the total area in
square feet that a
moving vehicle and
trailer exposes to
air resistance. The
chart shows the
limitations that must
be considered in
selecting a vehicle/
trailer combination.
Exceeding these
limitations may
significantly reduce
the performance of
your towing vehicle.


F-150
Base Vehicle Frontal Area (36.6 sq. ft.)
Without Trailer Tow Package or Payload Package
55 sq. ft.
Any Powertrain with Trailer Towing Package or Payload Package and
Trailer Towing Ratings Between 5,001 and 7,700 lbs.
60 sq. ft.
Any Powertrain with Trailer Towing Package or Payload Package and
Trailer Towing Ratings 7,701 lbs. and Greater
75 sq. ft.
All 5th-Wheel and Gooseneck Applications with Any Powertrain with
Trailer Towing Package or Payload Package
F-250/F-350/F-450/F-550 Super Duty
75 sq. ft.
All 5th-Wheel and Gooseneck Applications
60 sq. ft.
All Other Applications


I see nothing like that in the chevy towing guide.
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Old 06-21-2016, 09:42 AM   #56
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Also, the frontal area in Ford's towing guide allows more for a 5er than the TT. Not sure what is going on there. Without an explanation, it makes no sense.

I see this discussion has the engineer's panties in a bunch... LOL.


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Old 06-21-2016, 09:42 AM   #57
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In this case, at least its only saying your performance will be degraded if you exceed these recommendations. If you are using an anti-sway AND weight distribution, you would most likely negate a lot of the influence of the frontal area. That being said, every trailer is different in terms of frontal area, wind resistance, and drag and therefore, will influence the tow vehicle differently. Even things like humidity and elevation will make a difference since the density of air changes can change dramatically per the weather environment. Much like how a baseball jumps out of one stadium and is a warning track fly ball at another.
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Old 06-21-2016, 09:43 AM   #58
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[QUOTE=Major Malfunction;1233903
..............

In the end, physics and the math behind it are constants since the days Newton put them to paper. Calling BS, ignoring them, or using "gut feeling" does not make them go away. If the manufacturer says "don't do this", as an engineer I would tend to agree.
.............

[/QUOTE]

That's advice many are reluctant to follow.
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Old 06-21-2016, 09:54 AM   #59
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Originally Posted by 325BH View Post
Also, the frontal area in Ford's towing guide allows more for a 5er than the TT. Not sure what is going on there. Without an explanation, it makes no sense.

I see this discussion has the engineer's panties in a bunch... LOL.


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Without intimate knowledge, I would think its related to the fulcrum point and how the weight is leveraged. A TT is basically a balancing act and your fulcrum is out past the end of your truck. Hitch physics make some of that come forward towards your truck, but only so much. In the end, you have a dynamic load farther outside your center of gravity on a TT than on a 5th wheel which has its fulcrum more or less over the rear axle.

So that would mean the forces exerted by the 5th wheel are countered more efficiently by the tow vehicle since they are closer to the center of mass of the tow vehicle. Which is also why the same truck has a 5th wheel tow capacity significantly higher than towing a TT. Same truck but different physics being applied. A TT hitch can only handle so much weight and stress since it has to pick up the slack for being away from the center of mass. It's acting as your "elbow" and the trailer is in your fist. You can only handle so much weight before your elbow cannot control the weight.

A 5th wheel is much like if you put the weight on your shoulders rather than carrying in your hand. Its easier to control something closer to your body than it is further out. You can control more weight if you can get it closer to your center of mass just as much as its easier to counteract wind force if you can get your weight into it vs just your hand.

Cranes are no different. Once the boom starts going out, the capacity starts coming down because you get away from the controlling center of mass.
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Old 06-21-2016, 12:23 PM   #60
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Generally a 5er sits closer to the cab, even more so when using a short bed with a slider. A TT sits 9.5' to 11' back from the cab. Wind goes over the cab and then down to the tailgate. The frontal area on a TT is exposed to more wind than a 5er which is tucked in behind the truck. Even though the 5er is higher there's less exposed area.
JMOs but I get better mpg with my 5er than with the TT I had before.
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