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Towing Glossary

See Hitch Ball.

Ball height
Distance from the ground to the center of the hitch ball or the trailer’s hitch ball coupler when parallel to the ground while parked on a flat surface. This measurement helps you determine how much rise or drop you need in your draw bar.

Ball mount
Also called a draw bar, a ball mount is a removable hitch ball platform that slides into the receiver and fastens with a pin and “R” clip.

Ball shank
The threaded stud attached to the hitch ball that passes through the receiver or draw bar, on which the nut tightens to hold it in place. Conventional hitch balls come in three-quarter-inch and 1-inch diameter shanks.

Bolt-on hitch
A permanent hitch ball and bracket that are welded or bolted directly to the tow vehicle. Can be a fixed tongue hitch, which includes the ball and platform or a receiver style with a removable draw bar.

Bow eye
The steel loop on the front of a boat that the bow-strap hook attaches to. Bow roller The plastic wheel above the bow strap that provides a positive forward stop for a boat on a trailer.

Bow strap
The strap with the hook used to pull the boat tightly up against the bow roller. Brake controller Necessary when towing trailers with electric brakes. Electronic module inside the tow vehicle that controls electric trailer braking based either on inertia or a time delay from brake activation.

Bumper hitch
Some trucks and SUVs have a provision on their rear bumpers for attaching a hitch ball for towing. Good only for light-duty applications.

Cab-to-axle ratio
The measurement from the rearward-most portion of the cab to the center point of the hitch ball or coupler, which is located directly above or slightly forward of the rear axle. Standard requirements for a full-size bed are a minimum of 48 inches behind the cab. For using a short-bed pickup (less than or equal to 6 feet) to pull a fifth-wheel, the measurement can be as little as 38 inches with a pin box extensions (12-18 inches) and slide rails for the coupler.

Class I hitch
Trailer hitch with a capacity up to 2,000 pounds gross trailer weight, with up to 200 pounds of tongue weight.

Class II hitch
Trailer hitch with a capacity up to 3,500 pounds gross trailer weight, with 300 to 350 pounds of tongue weight.

Class III hitch
Trailer hitch with a capacity up to 5,000 pounds gross trailer weight with 500 pounds of tongue weight.

Class IV hitch
Trailer hitch with a capacity up to 10,000 pounds gross trailer weight, with 1,000 to 1,200 pounds tongue weight.

Class V hitch
Fifth wheel or gooseneck trailer hitch.

The forward most part of the trailer tongue that drops over the hitch ball and latches.

Curb weight
Also called wet weight, curb weight is the weight of a fully fueled vehicle, with all fluids, and no passengers or cargo on board.

The bar to which the hitch ball attaches. Comes in 1 1/4-inch and 2-inch square configurations depending on hitch class.

Fifth wheel hitch
A Class V hitch that mounts in the bed of a pickup. Although much smaller, the fifth-wheel system is similar in design to those used on tractor trailers.

A Class V hitch that mounts on a ball in the bed of a pickup to engage a coupler on a trailer. Ball sizes can be 2 5/16 inch or 3-inch.

Gross combined vehicle weight rating (GCVWR)
Total combined weight of truck and trailer, as specified by the vehicle manufacturer, including all passengers, fuel, fluids and cargo.

Gross trailer weight rating (GTWR)
The manufacturer-specified recommended maximum weight of a trailer when fully loaded.

Gross vehicle weight rating (GVWR)
The manufacturer-specified recommended maximum weight of a vehicle when fully loaded.

Hitch ball
The steel, ball-shaped piece over which the trailer coupler latches. Diameters are 1 7/8 inch, 2 inch, 2 5/16 inch and 3 inch.

When the truck and trailer may become damaged due to extremely acute turning angles. Usually occurs when backing.

The weight of passengers and cargo carried. Does not include vehicle or trailer weight, but it does include the tongue weight of the trailer. Equal to the difference between GVWR and curb weight.

Inserted through receiver and draw bar to lock draw bar in place. Usually secured with an “R” clip.

The receptacle of a trailer hitch into which you slide the draw bar. Comes in 1 1/4-inch and 2-inch square configurations depending on hitch class.

Receiver style hitch
Classified I, II, III and IV, it is a hitch with a receptacle that accommodates a drawbar or ball mount.

Safety chains
These chains attach to the eyelets adjacent to the receiver. They keep the trailer connected should the coupler come unhooked from the hitch ball.

Spring bar
Part of a weight-distributing hitch system that distributes trailer tongue loads to the tow vehicle’s forward axle.

Staging area
An area near a boat launch ramp that allows for loading and unloading of gear and passengers, which helps keep busy launch ramps from getting bogged down.

Surge brake system
Self-contained system used on trailers. Surge brakes have a master cylinder in the trailer coupler. When you apply the brakes in the tow vehicle, the initial slowing compresses the piston inside the master cylinder to apply braking force at the trailer wheels.

Sway control
A system that uses a shock absorber to resist side-to-side swaying movement of a trailer tongue sometimes caused by passing vehicles or cross winds.

Tandem axle
Two axles on a trailer.

The V-shape portion of the trailer that extends forward from trailer frame. Includes coupler.

Tongue weight
The downward weight applied by the towable equipment on the hitch ball. In general tongue weight should be around 7 to 8 percent of GTW and should not be more than 10 percent of the GTW.

Torsion bar
A type of suspension that uses bars that twist rather than coil or leaf springs. Weight-distributing hitch A receiver-style hitch system that includes additional equipment such as spring bars that work to distribute trailer tongue loads to the trailer axles and to the front axle of the tow vehicle.


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