When reviewing tow capacities published by truck manufacturers, fleet managers may notice a wide range available for each truck class. For example, ½-ton pickups can offer trailering capacities that range from 5,000 lbs. to more than 11,000 lbs.
Why such a large difference for the same size truck?
The answer lies in how the truck is spec'd and the type of trailer and hitch used. Put together the right combination and a truck can handle trailer loads with optimal power, efficiency, and safety. However, if the trailer weight exceeds the truck's capacity to pull it, the vehicle will encounter severe stress, leading to premature maintenance and component failure, and creating potential safety and liability issues, which could be costly to a company's bottom line.
How do fleet managers ensure they've properly equipped trucks to handle required towing requirements?
Five Questions to Define Towing Requirements
The starting point is to define exactly what requirements are needed for the trailer. Use these five questions as a guide:
1. What will be hauled in the trailer? Will it be a dense load, with loose rock or dirt? Will it be bulky construction or lawn debris? Will the trailer haul heavy equipment, such as a backhoe or excavator? Make a list of all possible cargo types planned to pull with that trailer - and what is anticipated to be placed on the trailer at the same time.
2. What are the cargo dimensions? This addresses cargo volume. Based on the dimensions of the payload, how much space is needed?
3. How much weight will be hauled? Look at a list of the different types of cargo the truck will need to haul. What are the estimated weights of each type? What quantity of each will be on the trailer at maximum load? What will that total payload weigh?
4. What type of trailer? Consider the cargo type. If hauling loose dirt, gravel, or construction debris, an open trailer would be a good fit. If the cargo needs protection from the elements or extra security, then select an enclosed trailer. For construction equipment or vehicles, a flatbed trailer often works best.
5. What is the total anticipated weight of the trailer and the cargo? Once cargo weight is calculated at maximum load, add the weight of the trailer. This determines the maximum towing capacity the vehicle needs to handle. As a general rule of thumb, add a buffer of at least 20-percent or more to capacity calculations to reduce risk of under-spec'ing the tow vehicle.
Once a clear idea of the weight and type of trailer a truck will need to pull, the next step is identifying the truck classification required to handle the load. Here are key terms to know when determining truck class:
■ As-spec'd curb weight. This factor is defined as the shipping weight of the truck or cab and chassis, without aftermarket upfits, including all standard equipment and options, fluids, and a full tank of fuel. Consult the truck's original equipment manufacturer (OEM) or dealer rep for curb weight estimates on chassis closest to spec requirements.
■ Gross vehicle weight rating (GVWR). This refers to the maximum allowable weight, as certified by the manufacturer, a vehicle can weigh (including all fluids, people, and cargo) to safely start and stop.
■ Payload capacity. This is the maximum amount of combined weight of cargo, equipment, and occupants a vehicle can safely carry. Calculate payload capacity by subtracting the vehicle's as-shipped curb weight from its GVWR. For example, if the GVWR is 19,500-lbs., and as-shipped curb weight is 9,500-lbs., the truck's payload capacity is 10,000-lbs.
Putting it Together
How is this all put together? If a truck's actual payload, including weight of occupants, is 2,000 lbs., and as-spec'd curb weight is 4,500 lbs., then the estimated gross vehicle weight (GVW) of the tow vehicle is 6,500 lbs.
What Class does this truck's GVW fit within? The following is a truck classification breakdown by GVWR:
■ Class 1: 0-6,000 lbs.
■ Class 2: 6,001-10,000 lbs.
■ Class 3: 10,001-14,000 lbs.
■ Class 4: 14,001-16,000 lbs.
■ Class 5: 16,001-19,500 lbs.
■ Class 6: 19,501-26,000 lbs.
■ Class 7: 26,001-33,000 lbs.
In the example above, the truck would fit within the Class 2 range.
Once the truck class is determined, what type of truck will best suit the fleet's application?
The following are vehicle types, segmented by truck classification:
■ Classes 1-2: Options include pickups, vans, SUVs, and smaller (single rear wheel) van cutaways.
■ Classes 3-4: Options include pickups (dual-rear-wheel), van cutaways, and medium-duty cab and chassis (including cab-forward and conventional cabs).
■ Classes 5-7: Medium-duty cab and chassis.
Now that the proper truck class and type is selected, the next factor to consider is gross combination weight rating (GCWR), which is the maximum allowable combined weight (as determined by the truck OEM) of the truck and its payload, with the trailer weight at maximum load.
GCWR is essential to calculating accurate tow capacity because it takes into account the tow vehicle's intended payload. Why is this important?
Most tow capacity charts published by truck OEMs don't account for a truck's specific application. When adding weight to the truck, this detracts from the vehicle's towing capacity.
For example, suppose a truck, at maximum load, has a GVW of 6,500 lbs. and its GCWR is 18,500 lbs. Subtract the GVW (6,500 lbs.) from the GCWR (18,500 lbs.) to come up with an estimated maximum towing capacity of 12,000 lbs.
An additional 500 lbs. to the truck's payload, which would bring the GVW to 7,000 lbs., would then reduce towing capacity by 500 lbs., to 11,500 lbs.
The tow vehicle's payload, therefore, directly impacts tow capacity. Lightening the truck's payload boosts towing capacity and vice versa.
However, how does all of this explain that ½-ton pickups, despite being the same size, offer such a wide variance in maximum towing capacities - from 5,000 lbs. to more than 11,000 lbs.? The differences lie in powertrain specification, including the engine, transmission, and rear (drive) axle ratio - all of which directly impact GCWR.
■ Engine. Which is the best engine choice for a fleet's towing requirements? For Class 1-3 trucks, the decision is usually between one diesel engine option and a variety of sizes of gas engines. As a general rule of thumb, the diesel offers the largest GCWR, and thus highest towing capacity because of its significantly higher torque. The downside is that the diesel option costs $8,000 more up-front than the gasoline-powered engine, so make sure the towing weight requires diesel.
For larger medium-duty trucks, especially in the Class 6-7 range, engine selection is a bit more complicated because there could be more than a dozen different diesel engine options to choose from, based on horsepower and torque, that determine GCWR.
■ Transmission. Should a manual or automatic transmission be spec'd? Depending on the vehicle type or manufacturer, options may not be available. In most cases, the automatic is the only transmission available. However, where there is an option, check with the vehicle manufacturer or dealer representative about which transmission will best handle your trailer load.
Also, for most Class 2-3 pickup trucks and vans, OEMs offer a tow package that includes a transmission cooler to help prolong transmission life when the truck is under constant, heavy loads.
■ Rear axle ratio. The rear axle ratio represents the relationship between driveshaft revolutions (driven by the transmission) and rear axle revolutions. Typically, the higher the ratio, greater pulling power is gained, but at the expense of fuel economy. The inverse often holds true. Lowering the ratio improves fuel economy, but sacrifices pulling power. Speak with a truck OEM rep to determine the ratio that best fits the fleet's trailering requirements and fuel efficiency objectives.
In addition to powertrain specs, here are other options to consider when selecting the right tow vehicle:
■ Two- or four-wheel drive. Will the truck and trailer need to operate in off-road conditions? If so, how often would the four-wheel drive need to be engaged for added traction?
These questions are important because the incremental cost for four-wheel drive can be as much as $4,000. Also, four-wheel drive adds substantial weight to the truck, diminishing payload and trailering capacity. Does the fleet's application warrant this extra cost and weight? If not, stick with two-wheel drive.
■ Rear suspension. If spec'ing a "smooth ride" suspension but keeping the truck under a constant heavy load pulling a trailer, there is a risk in creating premature maintenance issues and shortening the truck life. Select a rear suspension designed to handle the rigors of regular trailering.
■ Side-view mirror configuration. With full-size pickups and some full-size SUVs, there is an option for extendable side-view mirrors. These help improve visibility and safety, especially when pulling an enclosed trailer that may impede a driver's rear-view capabilities.
At this point, trailering requirements have been determined and a tow vehicle has been spec'd that's up to the task. What type of hitch will do the best job pulling that load?
■ Receiver hitch. This is the most common hitch type, with the hitch located below the rear bumper, often with a ball or heavy-duty pintle hook attached to it. This hitch allows a vehicle to pull a trailer without impacting cargo capacity in the pickup bed. There are two types of receiver hitches:
■ Weight-carrying hitch. Also known as a "dead-weight hitch," this hitch must support the trailer's full tongue weight, concentrated behind the truck's rear axle, making it best suited for light- to medium-sized loads.
■ Weight distributing hitch. Designed for heavier trailer loads, this hitch system includes spring bars that distribute the trailer's tongue weight from the vehicle's rear axle to the front axle, helping take stress off the rear of the truck and maximizing tow capacity.
■ Gooseneck hitch (for gooseneck trailers). This hitch is attached to the frame near the rear axle, nestled below the surface of the body. When you're not pulling the trailer, you can close the trap door, making it flush with the body, giving you the full surface area of the flat bed to haul cargo.
■ Fifth-wheel hitch (for fifth-wheel trailers). This hitch is a large horseshoe shaped plate, located at the center of the truck bed. The fifth-wheel hitch offers maximum towing capacity and is common for trucks used primarily as a trailer hauler.
Consult with both a truck OEM representative and trailer dealer to determine which type of hitch best fits the trailer, vehicle, and tow capacity requirements.
The Bottom Line
Just because published tow ratings for a vehicle may be 10,000 lbs., 12,000 lbs., or 20,000 lbs., does not necessarily mean that's what a fleet's truck can handle. Dig deeper, using the tips in this article, to calculate a precise towing capacity. This will help fleet managers put together a truck and trailer combination that hauls the load safely and efficiently.
Originally posted on Work Truck Online