How Much Can Your Vehicle Tow?

At first, it seems so easy. Your truck has an official maximum towing capacity, and you know how much your trailer weighs. If the trailer is less than the capacity, you are good to go, right? Alas, it is not that simple. MotorTrend elaborates in an article about towing with its Silverado 1500 ZR2 for a year. This Sharp Automotive Group post highlights what the outlet said. 

First, let’s discuss the consequences of towing a trailer that’s too heavy. It could damage your vehicle, the trailer, or both. You could also pose a threat to others on the road with you. At the very least, you are likely to experience considerable stress on your trip. 

Trailer Maximum Towing Capacity Is Just the Beginning 

Let’s start with the towing capacity rating. Marketing materials will often give you a maximum towing rating for the model line. Still, the figure depends on the vehicle’s weight, so it varies by vehicle configuration, diminishing as the vehicle weight increases. Consequently, 4×2 models will generally tow more than 4×4 models. Regular cabs will have a higher rating than crew cabs, and higher-equipped models will typically weigh more but tow less than more basic-equipped models.  

An exception is if that added equipment is a towing package. In addition to providing a hitch and wiring for the trailer’s lights and brakes, these packages will usually provide more robust cooling systems for both the engine and transmission, a possibly revised axle ratio, and other towing-focused features, which will increase the vehicle’s towing capacity. Your owner’s manual will have a table that should allow you to identify your vehicle’s maximum towing capacity. 

In MotorTrend’s case, the Duramax diesel-powered 2024 Silverado ZR2 has a maximum tow rating of 8,700 pounds. 

The next consideration is the trailer’s weight, which should be easy to determine. Any documentation should expressly state this information, and the trailer’s Vehicle Identification Number (VIN) plaque should also provide this information. 

“Stuff” to Consider 

You now have two figures, but both are based on an empty vehicle and an empty trailer. That brings in two additional figures that are important to anyone who tows. The first is the Gross Vehicle Weight Rating (GVWR). This is the vehicle’s weight, plus its payload and passenger weight. In MotorTrend’s example, its Duramax-diesel-powered ZR2 has a GVWR of 7,300 pounds. The truck itself weighs 5,770 pounds. Subtract that from the GVWR, and you will have your maximum payload of 1,530 pounds. Remember that the payload will include the passengers. So, to use round figures, if each of the five occupants in the truck weighs 200 pounds, that will leave you 530 pounds of cargo to put in the back. 

The following figure to know is the Gross Combined Weight Rating (GCWR). This is generally calculated by adding the vehicle’s Gross Vehicle Weight Rating (GVWR) to the maximum towing capacity.  But this is based on Gross Trailer Weight (GTW). So that is not just the trailer but everything you have loaded onto or into it. If you are towing a travel trailer, this will be everything you store inside, including clothes, cookware, tools, tank fluids, outdoor grilles, bicycles, e-bikes, or any other recreational equipment. This brings up another figure you will want to be aware of: the trailer’s Cargo Carrying Capacity (CCC). Fortunately, your RV is likely to have a high enough CCC to cover everything you want to bring. But if you are adding things to the roof or if the trailer has a toy box space in the rear for an ATV or whatever, that will all need to be considered as well. 

No one is likely to weigh everything he or she puts in either the trailer or truck, so you have to do some estimating and, if possible, find a certified scale you can drive upon to see if everything is under the GCWR. 

MotorTrend did just this. The author knew its trailer weighed about 8,200 pounds but was unclear on the amount of the additional equipment, so he sought out a vehicle scale. The scale produced a figure of 15,380 pounds, 380 pounds over the vehicle’s GCWR. His fix was to drain about half of the trailer’s 100 gallons of fresh water, which brought the combination under the limit. 

Another figure to consider is tongue weight, which is the weight upon the hitch itself. Ideally, it is about 10 to 15% of the gross trailer weight. Your trailer will be designed to stay within this margin, but what else you load onto it can impact that. Having a hefty load in the truck bed can also impact this. If you find your truck and trailer sagging where they come together, you will want to redistribute some of your cargo from your truck bed or front of the trailer to the rear.  

The Duramax Exhaust Brake 

MotorTrend takes some time to discuss the exhaust brake function of the Duramax diesel. This works by restricting airflow through the turbocharger via adjustable compressor vanes. The driver simply activates this when engaging the Tow/Haul drive mode by pressing the button in the center of the drive mode selector dial. The system uses vehicle sensors to determine pitch, yaw, acceleration, deceleration, etc., as well as determine if the truck is on a downhill grade and roughly how much weight is in tow. 

MotorTrend found the system useful, describing it thusly: “… it takes a fair bit of use of the service brakes before the grade braking and exhaust brake launch into service. However, once they do, the truck does an incredible job of downshifting into the correct gear, often a lower one than the driver might feel is necessary (exhaust brakes are more efficient at higher rpm), and automatically modulating the exhaust brake to maintain whatever the last desired speed was.” 

Terms 

Because we’ve thrown several weight terms and acronyms about, here is a list of relevant trailering weight terms and their definitions:  

Curb Weight —The curb weight of your vehicle is its weight with all of the standard equipment and necessary operating consumables (e.g., motor oil and coolant) and a full tank of fuel but without any passengers, cargo, or any other separately loaded items in it.  

Gross Combination Weight Rating (GCWR) —This is the maximum allowable weight of the tow vehicle and the trailer combined. The GCWR may be found in the Owner’s Manual or in the tow vehicle brochure for the model year you own, usually provided by the dealership. Some late-model vehicles may have a “Trailering Information” label providing the GCWR. The GCWR assumes that the tow vehicle and trailer have functioning brakes, with exceptions for very light trailers (typically less than 1,500 pounds).  

Gross Vehicle Weight Rating (GVWR) —The GVWR is the maximum allowable weight of the fully loaded vehicle, including liquids, passengers, cargo, and kingpin or tongue weight of any towed trailer. The GVWR is printed on the certification label and usually near the driver’s side door. This information can be found on the Trailering Information label on some late-model vehicles. GVWR primarily considers the weakest link in the load-bearing components, such as the frame, axles, springs, brakes, wheels, and tires. Based on the lowest component rating within the load-bearing components, manufacturers assign the GVWR. 

Gross Vehicle Weight (GVW)—The vehicle’s combined weight with all expected passengers, including cargo, a towing hitch installed, and full fluid tanks.  

Trailer Weight Rating (TWR) —This is the rated value for the maximum allowable weight of a loaded trailer for a specific tow-vehicle model and hitch type, as determined by the tow-vehicle manufacturer. A specific tow vehicle may have multiple TWRs for weight carrying, weight distributing, fifth wheel, and/or gooseneck hitch. A tow vehicle may also have a TWR for an unbraked trailer. 

Tongue Weight (TW) — The vertical load weight applied to a hitch. It should generally range between 10% to 15% of the trailer’s GVW.  

Pin Weight (PW) — This is the same as TW but for fifth-wheel trailers. Ideally, fifth-wheel trailers should range between 15% to 25% of the trailer’s GVW. The closer to 15%, the better. 

Tow-Vehicle Trailering Weight (TVTW) —Base vehicle curb weight of an estimated 150-pound driver and one 150-pound front seat passenger, plus 100 pounds of optional equipment split evenly between front and rear axles, plus the tow-vehicle manufacturer’s available trailering package and/or any required trailering content and representative aftermarket trailering equipment. 

Tow Ready Vehicle/Truck —The fully-loaded vehicle or truck with the driver and all passengers on board, all desired cargo onboard, necessary trailering equipment installed, and necessary vehicle fluid tanks or reservoirs filled to standard or full capacity. 

All three of the Sharp Automotive Group brands include full-size trucks and truck-based SUVs with significant towing ability. We hope all our towing customers become familiar with the above figures and how they pertain to their tow vehicle and trailer, and we wish all of you happy and safe towing.