Welcome to the VehicleTowCapacity.com technical glossary. The world of trailering and payload is full of complex acronyms, weight ratings, and jargon.
Understanding these terms is critical for safety. We have compiled these standard definitions based on automotive industry terminology found in manufacturer specification sheets and owner's manuals to help you use our research tool effectively.
Glossary
Technical Definitions
Listed alphabetically.
- Axle Ratio (Differential Ratio)
The relationship between the revolutions of the driveshaft and the revolutions of the rear (or front) axle. It is expressed as a number, such as 3.73:1, often shortened to "3.73."
Impact: A "higher" numerical axle ratio—sometimes confusingly called a shorter or taller gear—typically increases towing capacity and acceleration but reduces fuel economy at highway speeds. Identical vehicles can have different tow ratings purely because of their axle ratios.
- Body Style Segment
The classification category of the vehicle based on its size and configuration, such as Full-Size Truck, Compact SUV, or Mid-Size Sedan.
- Curb Weight
The total weight of a vehicle as manufactured, with all standard equipment and necessary operating consumables—including a full tank of fuel, oil, and coolant—but without passengers, cargo, or aftermarket accessories.
Impact: This number is the baseline for all subsequent weight calculations. The more optional equipment you add (moonroofs, power hitches, larger wheels), the higher the curb weight rises.
- Engine Displacement / Configuration
The volume of the engine's cylinders, measured in liters or cubic inches, and the arrangement of those cylinders, such as V6, V8, or I4.
- Fuel Type
The type of fuel or energy source the engine requires for operation, such as gasoline, diesel, electric, or hybrid.
- GCWR (Gross Combined Weight Rating)
The maximum permissible total weight of the loaded towing vehicle and the loaded trailer combined, as determined by the manufacturer.
Why it matters: Your total setup (Truck + Cargo + Passengers + Trailer + Trailer Cargo) must never exceed this rating.
- GVWR (Gross Vehicle Weight Rating)
The maximum permissible operating weight/mass of the vehicle itself, as specified by the manufacturer.
Why it matters: This includes the curb weight of the vehicle plus all passengers, cargo, fuel, and the tongue weight of any attached trailer. This is a critical safety number found on your driver's side door jamb sticker.
- HP (Horsepower) & HP RPM
Horsepower measures the engine's total power output. HP RPM is the engine speed, in revolutions per minute, at which the engine achieves that maximum power rating.
- Max Conventional Towing Capacity
The maximum weight a vehicle is rated by the manufacturer to tow using a standard frame-mounted or bumper-mounted receiver and a weight-carrying ball hitch.
Important: This rating applies to the total weight of the loaded trailer (GTW - Gross Trailer Weight). It is often only achievable if the vehicle is properly equipped with the manufacturer's required towing packages and a weight-distribution hitch system.
- Max Payload Capacity
The maximum amount of weight a vehicle can carry in addition to its curb weight.
Important: This includes the weight of the driver, all passengers, cargo in the trunk or bed, any aftermarket accessories (like a toolbox or topper), and the tongue weight of an attached trailer. This is often the most restricted weight rating, especially for passenger vehicles.
- Tongue Weight (Hitch Weight)
The downward force that the tongue of the trailer exerts on the hitch of the towing vehicle.
Impact: For safe conventional towing, tongue weight should typically be between 10% and 15% of the total loaded trailer weight. This weight is subtracted from your available Max Payload Capacity. Too little tongue weight can cause unsafe trailer sway; too much tongue weight can overload the tow vehicle's rear axle and suspension.
- Torque & Torque RPM
Torque is a measure of the engine's twisting force (turning power). It is the critical factor for starting a heavy load from a complete stop and for maintaining speed while climbing a grade. Torque RPM is the engine speed at which that maximum twisting force is achieved.