Towing Definitions


I know it must be frustrating for someone new to the hitching world to hear this strange new language called “Hitch Jargon”. I talk to customers on the phone every day who are desperately trying to communicate their needs to me but simply don’t know how to convey the proper words to describe what they want.

Eventually, after flailing about for a definition we can both understand, the light bulb flashes on and we can finally proceed!

So here, in a nutshell, are the towing definitions you need to understand to figure out what you need for your towing situation.


ADJUSTABLE BALL MOUNT
A special ball mount that slides into a Class III hitch that has the ability to be repositioned up or down as differing ball heights are required. Normally a bolt together or pin & clip adjustment hardware is utilized.
AXLE RATIO
The final drive gear ratio created by the relationship between the ring and pinion gears and the rotation of the driveshaft. In a 4.10:1 axle ratio, for example, the driveshaft will rotate 4.1 times for each rotation of the axle shaft (wheel). Often, a vehicle purchased with a “towing package” will have a different axle ratio from the regular model.
BALL MOUNT
The part of the hitch system that supports the hitch ball and connects it to the trailer coupler. The ball mount slides into the receiver hitch and is held in place with a pin and clip. Available in 1 ¼” and 2” square sizes. Also available in different drops or lifts to enable one to attain the perfect ball height for your trailer in order to tow as level as possible. Available in weight capacity ranges between 2000 lbs up to 14,000 lbs.
BRAKE CONTROLLER
A small control unit mounted inside the vehicle (normally under the dash near the drivers hand), that allows the action of the driver braking the tow vehicle to activate the trailer’s electric brakes. The unit can be adjusted to change the amount of voltage going back to the brakes and also to allow manual activation of the trailer’s brakes in emergency situations.
BREAKAWAY SWITCH
A safety device that activates the trailer brakes in the event the trailer becomes accidentally disconnected from the hitch while traveling.
COUPLER
The part of the trailer A-frame that attaches to the hitch ball.
ENGINE OIL COOLER
A heat exchanger, through which engine oil passes and is cooled by airflow. Sometimes offered in conjunction with a transmission-cooler.
FIFTH WHEEL TRAILERS
Trailers that are designed to be coupled to a special hitch that is mounted over the rear axle in the bed of a pickup truck. Can have 1, 2 or 3 axles and are the largest types of travel trailer built. Fifth wheel trailers can only be towed by trucks or specialized vehicles prepared for fifth wheel trailer compatibility.
FRAME MOUNT HITCH
Class 2, 3 & 4 hitches are designed to be bolted to the frame or cross member of the tow vehicle.
GOOSENECK TRAILERS
Trailers that are designed to be coupled to a special hitch that utilizes a ball mounted over the rear axle in the bed of a pickup truck.
GVWR- (Gross Vehicle Weight Rating)
The total allowable weight of a vehicle, including passengers, cargo, fluids and hitch weight.
HITCH RATINGS
Hitches are rated by the manufacturer according to the maximum amount of weight they are engineered to handle. Class I trailer hitches are rated for towing between 1000 and 2000 lbs. Class II hitches are rated for loads up to 3500 lbs. Class III hitches are rated for between 3500 and 6000 lbs off a regular ball mount, up to 10,000 lbs with a weight distributing system. (See “weight distributing hitch”). Class IV hitches are rated from 8000 to 10,000 lbs off a heavy duty ball mount, up to 14,000 lbs with a weight distributing hitch system. Different hitch manufacturers rate their hitches differently, hence the range of capacities in this definition. For fifth wheel trailer hitches, the weight capacity ranges from 12,000 lbs up to 25,000 lbs. (This figure refers to the total weight of the trailer, with water tanks full, all supplies on board and ready to roll.) Gooseneck hitches can be rated up to 30,000 lbs.
HITCH WEIGHT
The amount of weight directly on the hitch itself when the trailer is coupled. Sometimes referred to as “tongue weight”. Hitch weight for a travel trailer can be 10-15% of overall weight. Fifth wheel hitch weight is usually 18-20% of the overall weight.
NCC-( Net Carrying Capacity)
Maximum weight of all passengers (if applicable), personal belongings, food, fresh water, supplies—derived by subtracting the UVW (unloaded vehicle weight) from the GVWR (Gross vehicle weight rating).
PAYLOAD CAPACITY
The maximum allowable weight that can be placed in or on a vehicle, including cargo, passengers, fluids and fifth-wheel or conventional hitch loads.
RECEIVER
That portion of the trailer hitch that permits a hitch bar or shank to be inserted. The receiver may be either 1 1/4”, 1 5/8”(rare), 2”, or 2 ½” square, the smallest being termed a mini-receiver.
SAFETY CHAINS
A set of chains that are attached to the trailer A-frame and must be connected to the tow vehicle while towing. Safety chains are intended to keep the trailer attached to the tow vehicle in the event of hitch failure, preventing the trailer from complete separation. They should be installed by crossing the chains in an X pattern, so the coupler is held off the road in the event of a separation.
SHANK
Also called a hitch bar, ball mount or stinger, the shank is a removable portion of the hitch system that carries the ball or adjustable ball mount, and slides into the receiver.
SPRING BAR
Component part of a weight distributing hitch system, the spring bars are installed and tensioned in such a manner as to distribute a portion of the trailer’s hitch weight to the front axles of the tow vehicle and to the axles of the trailer.
SWAY
Fishtailing action of the trailer caused be external forces that set the trailer’s mass into a lateral (side-to-side) motion. The trailer’s wheels serve as the axis or pivot point. Also known as “yaw”.
SWAY CONTROL
Devices designed to damp the swaying action of a trailer, either through a friction system or a “cam action” system that slows and absorbs the pivotal articulating action between tow vehicle and trailer.
TAIL SWING
Motorhomes built on chassis with short wheelbases and long overhangs behind the rear axle are susceptible to tail swing when turning sharply. As the motorhome moves in reverse or turns a corner, the extreme rear of the coach can move horizontally and strike objects nearby (typically road signs and walls). Drivers need to be aware of the amount of tail swing in order to prevent accidents.
TONGUE WEIGHT
The amount of weight imposed on the hitch when the trailer is coupled.
TOW BAR
A device used for connecting a vehicle to the motorhome when it’s towed with all four wheels on the ground.
TOW RATING
The manufacturer’s rating of the maximum weight limit that can safely be towed by a particular vehicle. Tow ratings are related to overall trailer weight, not trailer size in most cases. However, some tow ratings impose limits as to frontal area of the trailer and overall length. Tow ratings are determined by the vehicle manufacturer according to several criteria, including engine size, transmission, axle ratio, brakes, chassis, cooling systems and other special equipment.
TRAILER BRAKES
Brakes that are built into the trailer axle systems and are activated either by electric impulse or by a surge mechanism. The overwhelming majority of RV’s utilize electric trailer brakes that are actuated when the tow vehicle’s brakes are operated, or when a brake controller is manually activated. Surge brakes utilize a mechanism that is positioned at the trailer coupler, that detects by inertia force when the tow vehicle is slowing or stopping, and activates the trailer brakes via a hydraulic system (typically used on boats).
TRAVEL TRAILER
Also referred to as “conventional trailers”, these types of rigs have an A-frame and coupler and are attached to a ball mount on the tow vehicle. Travel trailers are available with one, two or three axles. Depending upon tow ratings, conventional trailers can be towed by trucks, cars or sport utility vehicles (SUV’s).
UVW- (Unloaded Vehicle Weight)
Weight of the RV including factory-installed options, with full LP-gas tank or cylinders. Does not include gasoline or diesel fuel, fresh water or accessories installed by the dealer.
WEIGHT CARRYING HITCH
Also known as a “dead weight” hitch, this category includes any system that accepts the entire hitch weight of the trailer. In the strictest sense, even a weight-distributing hitch can act as a load-carrying hitch if the spring bars are not installed and placed under tension.
WEIGHT DISTRIBUTING HITCH
Also known as an “equalizing” hitch, this category includes hitch systems that utilize spring bars that can be placed under tension to distribute a portion of the trailer’s hitch weight to the tow vehicle’s front axle and the trailer’s axles.
WIRE HARNESS
The electrical umbilical cord that connects the tow vehicle to the trailer, supplying electricity to the trailer’s clearance and brake lights, electric brakes and a 12-volt power line to charge the trailer’s batteries.

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