| Towing glossary |
Ball
mount - The part of the hitch system that supports
the hitch ball and connects it to the trailer coupler.
Ball mounts are available in load-carrying and weight-distributing
configurations. An adjustable ball mount allows a
hitch ball to be raised, lowered and tilted in small
increments to allow fine tuning of the spring bar
setup and to compensate for tow vehicle "squat,"
which occurs after the trailer coupler is lowered
onto the ball.
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Base
Curb Weight (BCW) - BCW is the weight of a vehicle
with standard equipment and a full tank of fuel. It
does not include passengers, cargo or optional equipment.
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Brake
controller - A control unit mounted inside your
RV that allows electric trailer brakes to become activated
in harmony with the braking of the tow vehicle. This
device can be used to adjust trailer brake intensity,
or to manually activate the trailer brakes.
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Breakaway
switch - A safety device that activates the trailer
brakes in the event the trailer becomes accidentally
disconnected from the hitch while traveling.
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Cargo
Weight (CW) - The cargo weight includes all the
weight added to the Base Curb Weight (BCW), including
the passengers, the cargo and any optional equipment.
When towing, the trailer tongue weight also has to
be included in the cargo weight.
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Class
A motorhome - An RV with the living accommodations
built on or as an integral part of a self-propelled
motor vehicle. Models range from 24 to 40 feet long.
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Class
B motorhome - Also known as a camping van conversion.
These RVs are built within the dimensions of a van,
but with a raised roof to provide additional headroom.
Basic living accommodations inside are ideal for short
vacations or weekend trips. Models usually range from
16 to 21 feet.
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Class
C motorhome - An RV with the living accommodations
built on a cutaway van chassis. A full-size bed in
the "cabover" section allows for ample seating,
galley and bathroom facilities in the coach. Also
called a "mini-motorhome" or "mini."
Lengths range from approximately 16 to 32 feet.
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Coupler
- The part of a trailer A-frame that attaches
to the hitch ball.
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Curb
Weight (CW) - Also known as Net Weight. The weight
of the RV as it is sitting on the lot, without the
personal load you will be adding.
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Dinghy
- A vehicle towed behind a motorhome, sometimes
with two wheels on a special trailer called a tow
dolly, but often with all four wheels on the ground.
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Dry
Weight (DW) - The weight of the RV without adding
fuel, water, propane, supplies and passengers. The
manufacturers UVW will not include any dealer-installed
options. Also known as Unloaded Vehicle Weight.
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Dually
- A pickup truck, or light-duty tow vehicle, with
four tires on one rear axle.
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Dullies
- Dual Tires.
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Engine
oil cooler - A heat exchanger, similar to a small
radiator, through which engine oil passes and is cooled
by airflow.
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Fifth-wheel
trailers - Fifth-wheel trailers are trailers designed
to be coupled to a special hitch that is mounted over
the rear axle in the bed of a pickup truck. These
trailers can have one, two or three axles and are
the largest type of trailer built. Because of their
special hitch requirements, fifth-wheel trailers can
only be towed by trucks or specialized vehicles prepared
for fifth-wheel trailer compatibility.
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Frame-mount
hitch - Class II and higher hitches are designed
to be bolted to the vehicle frame or cross members.
This type of hitch may have a permanent ball mount,
or may have a square-tube receiver into which a removable
hitch bar or shank is installed.
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Gross
Axle Weight (GAW) - The total weight supported
by each vehicle's axle (front or rear). To obtain
this number, you have to weigh the vehicle and the
trailer on a scale.
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Gross
Axle Weight Rating (GAWR) - The manufacturer's
rating for the maximum allowable weight that an axle
is designed to carry. GAWR applies to tow vehicle,
trailer, fifth-wheel and motorhome axles.
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Gross
Combined Weight (GCW) - The actual weight of a
vehicle and trailer combined. To obtain this number,
you have to weigh the vehicle and the trailer together
on a scale.
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Gross
Combination Weight Rating (GCWR) - The maximum
allowable weight of the combination of tow vehicle
and trailer/fifth-wheel, or motorhome and dinghy.
It includes the weight of the vehicle, trailer/fifth-wheel
(or dinghy), cargo, passengers and a full load of
fluids (fresh water, propane, fuel, etc.).
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Gross
Trailer Weight (GTW) - Gross trailer weight is
the weight of the trailer fully loaded in its actual
towing condition. GTW is measured by placing the fully
loaded trailer on a vehicle scale. The entire weight
of the trailer should be supported on the scale.
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Gross
Vehicle Weight (GVW) - The actual weight of a
vehicle when fully loaded. (Base Curb Weight + Cargo
Weight)
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Gross
Vehicle Weight Rating (GVWR) - The total allowable
weight of a vehicle, including passengers, cargo,
fluids and hitch weight.
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Hitch
ratings - Hitches are rated by the manufacturers
according to the maximum amount of weight they are
engineered to handle. Class I travel trailer hitches
are rated for towing as much as 2,000 pounds. Class
II units are for loads up to 3,500 pounds. Class III
has a rating of 7,500 pounds, and Class IV is for
loads of up to 10,000 pounds. Class V hitches are
designed for towing loads up to 14,000 pounds. These
ratings may vary depending on the manufacturer. Fifth-wheel
ratings range to 25,000 pounds. The weight rating
refers to the total weight of the trailer/fifth-wheel,
with freshwater tank full, propane tanks full, all
supplies on-board and ready to travel.
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Hitch
weight - The amount of weight imposed on the hitch
when the trailer is coupled. Also referred to as "tongue
weight". Hitch weight for a travel trailer can
be 10-15 percent of overall weight; fifth-wheel hitch
weight is usually 18-20 percent of the overall weight.
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Light
Weight RV - RVs that are designed to be easily
towed behind most Minivans, light-duty trucks and
cars! The most common being a pop-up trailer.
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Maximum
Loaded Trailer Weight - The maximum allowable
fully loaded weight of a trailer. (GCWR - GVW).
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Net
Carrying Capacity (NCC) - The amount of cargo,
passenger and fluid weight that can be added to an
RV without exceeding its GVWR. The NCC label in an
RV may not include the weight of dealer installed
or factory installed options already on the vehicle.
Subtract UVW from the GVWR and the result is what
can be added to the factory weight.
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Receiver
- The portion of a hitch that permits a hitch bar
or shank to be inserted. The receiver may be either
11/2-, 15/8- or 2-inch square; the smallest being
termed a mini-hitch.
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Safety chains - A set of chains that are attached
to the trailer A-frame and 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 using an X-pattern
(criss-crossed) so the coupler is held off the road
in the event of a separation.
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Shank
- Also called a hitch bar or stinger. A shank is a
removable portion of the hitch system that carries
the ball or adjustable ball mount, and slides into
the receiver.
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Spring
bar - Component parts 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 axle of the tow
vehicle and to the axles of the trailer.
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Sway
- Refers to the "fish-tailing" action of
a trailer caused by 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".
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Sway
control - Devices designed to damp the swaying
(fish-tailing) 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. The most common device
in use is a "sway bar".
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Tail
swing - All 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, its extreme rear 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.
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Tongue
Weight (TW) - The amount of weight imposed on
the hitch when the trailer is coupled. Also referred
to as "hitch weight". Tongue weight for
a travel trailer can be 10-15 percent of overall weight;
fifth-wheel hitch weight is usually 18-20 percent
of the overall weight.
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Tow
bar - A device used for connecting a dinghy vehicle
to the motorhome when it's towed with all four wheels
on the ground.
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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.
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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 RVs 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 positioned at the
coupler that detects when the tow vehicle is slowing
or stopping and activates the trailer brakes via a
hydraulic system.
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Transmission
cooler - A heat exchanger similar to a small
radiator through which automatic transmission fluid
passes and is cooled by airflow. |
Travel
trailer - Also referred to as "conventional
trailers" these types of trailers 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.
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Umbilical
cord - The wiring harness that connects the tow
vehicle to the trailer, supplying electricity to the
trailer's clearance and brake lights, electric brakes
and a 12-volt DC power line (to charge the trailer's
batteries).
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Unloaded
Vehicle Weight (UVW) - The weight of the RV without
adding fuel, water, propane, supplies and passengers.
The manufacturers UVW will not include any dealer-installed
options. Also known as Dry Weight.
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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.
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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.
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Wet
weight - The weight of the vehicle with the fuel,
freshwater and propane tanks full.
Wheelbase - The distance between the center lines
of the primary axles of a vehicle. If a motorhome
includes a "tag" axle, the distance is measured
from the front axle to the center point between the
drive and "tag" axle.
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Wheelbase
- Distance between center lines of the primary
axles of a vehicle. If a motorhome includes a tag
axle, the distance is measured from the front axle
to the center point between the drive and tag axles.
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Yaw
- Refers to the "fish-tailing" action of
a trailer caused by 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 "sway".
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