Why a Big Truck

The scarcest statement I can hear from an uninformed RVer with a fifth-wheel (FW) trailer is “my truck can easily pull my trailer.”  Why, because pulling should be one of the last considerations for selecting a truck.

See A Sad Story for what can happen.

So what are the important considerations for selecting a FW tow vehicle?  First, we should start with some terms:

GAW	Gross Axle Weight – the maximum weight that axle can hold
GVW	Gross Vehicle Weight - the total of the weight on the axles, the weight of the vehicle on the ground.  In the case of a trailer, the axle weight plus the weight being transferred to the tow vehicle
GVWR	Gross Vehicle Weight Rating – the maximum weight the vehicle can weigh
UVW	Unloaded Vehicle Weight – the weight of the vehicle as built, empty
NCC	Net Carry Capacity – usually the difference between GVWR and UVW
GCW	Gross Combined Weight – the combined weight of the tow vehicle and the vehicles being towed
GCWR	Gross Combined Weight Rating – the maximum combined weight of the tow vehicle and the vehicles being towed

We will be using the term Dually pickup to mean the top end of the weight class for the pickup brand with dually wheels for extra weight capacity.

Now, here are some statistics on Dually crewcab pickup trucks with diesel, automatic, and 8’ beds: (note, these are not easy to find numbers, Ford is the easiest)

Lbs	Chevrolet 3500 2007	Ford F350SD 2008	Dodge 3500 2007
GVW	11,400	13,000	9,900
Curb Weight	6,231	7,710	6,927
Net Cargo Cap	5,169	5,290	4,541
Max 5th W Trailer Weight	16,000	19,500	15,900
GCWR	23,500	28,000	23,000

We should note that in many states, a truck over 10,000 GVWR is considered a commercial vehicle (no matter how it is used) which affects license plates and insurance.

Not only are the manufacturers vague in publishing weight numbers, but they also hedge on what they do say.  For example, the following is a direct quote from Ford’s RV And Trailer Towing Guide for 2007.

“Maximum Loaded Trailer Weight is the highest possible weight of a fully loaded trailer the vehicle can tow, based on a minimum towing vehicle GVW. It assumes a towing vehicle with any mandatory options, no cargo, tongue load of 10-15% (conventional trailer) or king pin weight of 15-25% (fifth-wheel trailer), and driver only (150 lbs.). F-Series Super Duty chassis cab models also assume a second-unit body weight of 1,000 lbs. Weight of additional options, passengers, cargo, and hitch must be deducted from this weight.

Gross Combined Vehicle Rating view

Let’s determine the actual trailer capacity from the maximum weight pulled:

Lbs	Chevrolet 3500 2007	Ford F350SD 2008	Dodge 3500 2007
Curb Weight	6,231	7,710	6,927
Add fuel, passengers, some stuff	1,220	1,220	1,220
GCWR	23,500	28,000	23,000
Remaining Trailer weight	16,391	19,070	14,853
Maximum 5th Wheel by Manufacturer	16,400	19,500	15,900

Gross Vehicle Rating view

Now let’s determine the actual trailer capacity from the view of what the maximum trailer pin weight can be.  Normally the trailer pin weight should be around 20% to 25% of the total trailer weight so we could say the trailer can be up to five times the pin weight up to the limit of the GCWR of the truck.  We will use 20% for comparisons.

Lbs	Chevrolet 3500 2007	Ford F350SD 2008	Dodge 3500 2007
Curb Weight	6,231	7,710	6,927
Add fuel, passengers, some stuff	1,220	1,220	1,220
GVWR	11,400	13,000	9,900
Remaining Trailer Pin weight	3,949	4,070	1,753
Effective Trailer Weight	19,745	20,350	8,765
Maximum 5th Wheel by Manufacturer	16,400	19,500	15,900

The added "some stuff" includes things like; spare tire (an option), your weight above 150 lbs (the standard), your mate, extra fuel tank, and tools.

Now, a listing of the weight of the trailers we are considering remembering that the tow vehicle has to be qualified from a GCWR and a GVWR aspect:

		GVWR	Pin Weight
	Alfa Leisure	18,500	2,400
	Carriage	18,600	3,000
	King of the Road	20,000	3,100
	Newmar Kountry Aire	20,000	3,100
	NuWa Hitchhiker	17,900	3,200
	Teton	20,000	2,900
	Travel Supreme	19,900	2,600

In the years we have been doing this research, we have observed the weights capacities of pickups rising, each in response to the others increases.  We should note that the specs above are for trucks that have heavier capacities than a Dually.  But we have not seen a concurrent increase in drivetrain capacities.  But what is the real issue if not GVWR or GCWR, because you can see these FW trailers being towed by Dually pickups all the time?  The issue is the stopping and handling capacity of the truck.

When we first started looking at RVs, we were open to fifth-wheel (FW) trailers and motorhomes.  At the first RV show, we were in a National Seabreeze FW and the dealer rep asked what we would pull it with.  I indicated that I had a Chevrolet Silverado ¾ ton 4x4.  The rep said that if I did it right, I would have to get a Medium Duty Truck (MDT).

The next year I spent time researching MDTs and came to respect the reason the rep told me why I would need a MDT for the size trailer we had been talking about.  The next show I asked the same dealer rep what prompted him to get a MDT and he replied, “The second time my trailer pushed my pickup through an intersection.”

Most people look at the horsepower as the big issue and have felt that, with the new diesels that Ford and Chevrolet are using, they can easily pull big trailers even up hills.  But can the pickup control the combined vehicle weight, when steering and braking?  Pulling a heavy trailer with a pickup means you are over-stressing the truck.  Things will break. Expensive things like the transmission.

There are many add-ons to increase the horsepower of the engine.  But the frame and the brakes are as they come, and even the transmission does not have capacity increasing add-ons.

If you ever plan to travel in the mountains, the drive trains of these pickups, even with tow mode transmissions, will require you use your brakes to control your speed downhill.  Compare that to a tow vehicle with an engine brake where engine braking is used to control downhill speeds leaving your brakes for emergencies.  

Probably the biggest reason to be concerned about having a properly sized tow vehicle is the litigious world we live in.  If you get involved in an accident, even one that was not your fault, and you are over-weight, you are severely exposed to legal action.  To start, the authorities may choose to cite you for operating an unsafe vehicle.  Then your insurance company can choose to not cover you.  And finally, there is always a lawyer looking to get money from someone who was in the wrong. See Sad Story

Some Canadian Provinces and a few states are starting to stop and check the weights of RV rigs to see if they are within the GVWR and GCWR ratings of the vehicles.

Conclusion

So, if a Dually is not up to the job of pulling a heavy FW trailer, what do you need?  The answer is a Medium Duty Truck (MDT).