Trailer Components and Towing Gear

Connection first: ball, coupler and receiver ratings

Towing starts with the connection between vehicle and trailer. The ball diameter must match the coupler, commonly 1-7/8, 2 or 2-5/16 inches, and the ball mount, receiver and tow vehicle each have their own weight rating. The weakest rating sets the limit. Tongue weight, the downward load on the ball, must also stay within the hitch's rating, so check it as well as the total.

Safety chains cross under the coupler and hook to the tow vehicle, and in many places a trailer with its own brakes also needs a breakaway system. Coupler locks are sized to the latch, so measure it before buying. Make sure every part in the chain is rated above the loaded trailer weight. Balls, mounts and couplers are listed under trailer hitches and couplers.

Lights, brakes, bearings and levelers

Trailer wiring uses a 4-pin flat plug for lights only or a 7-way plug that adds electric brakes, reverse lights and a 12 V feed, so match the plug to your vehicle's socket. Electric brakes need a brake controller in the tow vehicle. Wheel bearings and seals are the main wear items on an axle, and a kit lists the bearing and seal numbers, which must match the hub. Connectors and brake parts are grouped under trailer brakes and wiring connectors.

Jacks and levelers hold the trailer steady once it is parked. A tongue jack lifts the coupler off the ball, stabilizers stop rocking, and leveling feet, blocks or ramps correct the slope. Check the working load of any jack, stand or block. Small adjustable feet with M6 or M8 threads belong on furniture and cabinets, not on a loaded trailer.

Questions about Trailer Components and Towing Gear

What is tongue weight and why does it matter?

Tongue weight is the downward force the trailer puts on the hitch ball. Too little makes the trailer sway, and too much overloads the rear axle of the tow vehicle. On a conventional trailer it is typically about a tenth to a seventh of the loaded trailer weight.

Do all trailers need brakes?

It depends on the trailer's weight and local law, which set the weight above which brakes are required. Heavier trailers usually need brakes on at least one axle, an electric brake controller in the tow vehicle and often a breakaway switch. Check the rules where you tow.

Which trailer plug do I need, 4-pin or 7-way?

Match the plug on the tow vehicle, with an adapter if the trailer's plug differs. A 4-pin flat plug handles lights only. A 7-way plug adds brake control, reverse lights and a 12 V supply, so it is needed for a trailer with electric brakes or accessories.