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Trailer Towing Terms

We've compiled a list of terms and their definitions relevant to open and enclosed trailers. Although not an exhaustive list, it does include the most common trailer terms. If there are any we've omitted, please add them in the comments section.

GVWR or Gross Vehicle Weight Rating - total weight of the trailer by a manufacturer as the recommended maximum weight of a vehicle plus the weight of the load placed on the trailer (although the gross vehicle weight rating of a truck is the total weight of the truck, trailer, and the load on the trailer).

GAWR or Gross Axle Weight Rating - maximum distributed weight that can be supported by a given axle.

GTW or Gross Trailer Weight - actual weight of a fully loaded trailer, which includes the weight of the trailer itself along with everything loaded on or in it.

Tongue Weight - downward force exerted on the hitch ball by the trailer coupler. It is roughly 10-15% of the GTW.

Payload Capacity - total weight of the cargo you can add to the trailer safely. (GVWR - Empty Weight = Payload Capacity)

For the Weights & Capacities chart, click here.

White Nissan Titan hitched to a charcoal gray Diamond Cargo Trailer. Location is at Diamond Cargo Mfg. Plant
Hauling Diamonds

DOT/NHTSA: abbreviations for the Department of Transportation and National Highway Traffic Safety Administration, respectively. They regulate all Federal motor vehicle laws and regulations.

Manufacturers Certificate of Origin (MOC): A MOC is supplied by the motor vehicle manufacturer and is used to register a trailer with the owner’s local department of motor vehicles to receive a license plate and title for proof of ownership.

Vehicle Identification Number (VIN): number generated by a motor vehicle’s manufacturer for the purpose of tracking the date and place a trailer was manufactured. It is located on the MOC and the VIN label is attached to the trailer. The VIN label will include certain information required by the DOT/NHTSA and is also where you will find your trailer’s GVWR.

Bumper Pull: A trailer that attaches to a hitch and ball that is attached to the tow vehicles frame or bumper.

Gooseneck: A trailer that attaches to a hitch ball in the bed of a truck over the rear drive axle.

Cargo Trailer: or Enclosed Trailer, a trailer whose cargo area is protected from the elements.

Enclosed Trailer: or Cargo Trailer, a trailer whose cargo area is protected from the elements.

Utility Trailer: Also referred to as an Open Trailer, a trailer whose cargo area is not protected from the elements and cargo area is accessible from all sides.

Dump Trailer: A trailer with a hydraulic dump system. Typically meant to haul dirt, debris, and various other materials.

Flat Bed / Deckover Trailer: A trailer that’s surface extends over/above the wheelbase. This allows it to use maximum available width allowed on the road.

Car Hauler: A trailer that hauls other vehicles. Can be enclosed or open.

Landscape Trailer: A trailer for hauling landscape equipment, typically similar to an open utility trailer.

Tire Size: The outside diameter of the rim’s dimensions. The overall diameter of the tire can change depending on the manufacture of the tires wall height and thickness.

Bias Ply: A tire having a foundation of plies of rubberized cords in a crisscross pattern of lines diagonal to center line of the tread.

Axle: A bar connecting two opposite spindles holding hubs and wheels.

EZ Lube: Axles that have a grease fitting installed inside the spindle that allows an easily accessible grease point for wheel bearing lubrication.

Coupler: A locking mechanism used to connect the trailer tongue tube to the ball of the towing vehicle. Couplers may come in many different shapes and sizes, but the most common sizes are 1-7/8″, 2″ and 2-5/16″. The coupler and hitch ball must be compatible.

Leaf Spring: A spring consisting of several layers of flexible metallic strips joined to act as a single unit.

Spring Hanger: A U-shaped piece of metal used to attach leaf springs to the frame.

Shackle: A flat piece of metal used to connect the leaf spring to the Spring Hanger eliminating a binding action when the spring becomes compressed. Typically used in a pair.

Spindle: A rod that serves as an axis point for the revolving hubs connected to the axle bar.

Hub: The center connecting part between the wheel and the wheel bearings acting as a focal point.

Wheel Bearing: A structural part that supports the connection of the spindle and the hub together reducing friction and wear.

Wheel Grease: thick oil used for lubricating the wheel bearings adding longevity to the wheel life.

Bearing Protectors: Commonly referred to as bearing buddies, the purpose is to replace the dust cap so that wheel bearings can be easily grease.

Dust Cap: Used to cover the hub center to prevent dust and dirt from entering the grease inside the wheel bearings.

Lug Nuts: A heavy, rounded nut that fits over a lug stud to attach a wheel to the hub.

Lug Studs: A bolt installed from the back side of the hub to secure a wheel to the hub by using lug nuts.

Single Rear Door: A door that is hinged from one side.

Double Rear Door: A door that is hinged on both sides and closes in the middle with a cam bar.

Rear Ramp Door: A door that is hinged on the bottom and lowers with spring and cable assist for easy loading and unloading of material.

Rear or Side Ramp Gate: A gate that is hinged on the bottom that allows for easy loading and unloading of material generally covered with an expanded metal surface.

Rear or Side Ramps: Generally, two independent ramps that are stored by either slide in or fold up styles with the trailer allowing you to load or unload items with different widths.

Safety Chains: chains connected from the trailer tongue to the tow vehicle and are used to safely guide the trailer in the event of a ball or coupler failure.

Wheel Grease: A thick oil used to lubricate the wheel and wheel bearings to help increase the wheel life.

Stone Guard: Metal/aluminum tread plating on the front of most of our enclosed trailer. Protects the exterior of your trailer from rocks, dirt and debris.

ATP: Aluminum Tread plating

RTP: Rubber Tread Plating

Dove Tail – Slight incline at rear of some utility and equipment trailers

Curb Side – The passenger side of your trailer in the US.

Street Side – The driver’s side of your trailer in the US.

Pintle Hitch – A pintle hitch is a type of tow hitch that uses a ring-to-hook or ball configuration for a more secure mount that's ideal for rougher terrain.

V-Nose : A common description for the front end of an enclosed trailer. Unlike traditional flat front trailers, the v-nose is as the name implies, it comes to "V" at the front of the trail for aerodynamic purposes to better "cut" through the air as it is towed down the road. An additional benefit is the fact that you get a couple extra square feet of space inside the nose of trailer.

Side Rails: Typically seen on open utility trailers to contain cargo.

Single Axle: Only one axle/set of wheels.

Tandem Axle: Two axles with a single set of wheels (2 wheels total per axle), which increases hauling capacity and stability.

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