Hitches, Receivers and Ball Mounts

Most towing confusion lives in this category, and almost all of it comes from four numbers that get used interchangeably when they are not interchangeable: the hitch class, the receiver tube size, the ball diameter, and the drop or rise of the ball mount. Get those four right and the hardware side of towing is essentially solved.

The two that get mixed up most often are class and receiver size. They correlate but they are not the same thing: a 2 in receiver opening appears on Class 3, Class 4 and some Class 5 hitches. The tube tells you what fits; the class tells you what it is rated to pull. Never infer one from the other.

A coupler stamped 2 in goes on a 2 in ball. Not a 1-7/8 in ball that looks close enough, and not a 2-5/16 in ball that will not latch. An undersized ball in an oversized coupler is the classic way trailers come off, because the coupler can lift over it under the right combination of bump and brake.

Ball ratings matter too, and they are independent of the mount's rating. CURT publishes its 2 in stainless ball on a 1 in shank at a 6,000 lb capacity with a 250 ft-lb mounting torque - which is a genuinely high torque figure, and the reason a ball tightened by hand with a crescent wrench is a real failure mode rather than a theoretical one.

• Fixed mounts. One drop, one ball, one piece. Nothing to rattle, nothing to torque, cheapest and lightest. Right answer if you own one trailer and one tow vehicle.
• Adjustable channel mounts. A channel with pinned height positions and often two ball sizes. The answer when the driveway contains a boat trailer, a utility trailer and a camper that all sit at different heights.
• Pivoting or stowing mounts. Fold up under the bumper when not in use, which solves the shin-height steel bar problem in parking lots.
• Mounts with built-in scales. An adjustable drop hitch with a gauge in the shank reads tongue weight as you lower the trailer onto the ball, turning the most-skipped step in towing into something automatic.

Capacity, adjustability and material. A plain 7,500 lb loaded ball mount costs very little because it is one forging. A 14,000 lb adjustable channel mount with two balls costs several times as much because it is heavier steel with more machined parts. Aluminum adjustable mounts cost more again and buy you one thing: you can actually lift them.

Buying the mount before measuring the drop. The measurement is simple - with the trailer sitting level on its jack, measure from the ground to the bottom of the coupler, then from the ground to the top of your receiver tube - but almost nobody does it first, and the result is a trailer that tows nose-high with too much weight on its rear axle. A nose-high trailer is a trailer with reduced tongue weight, and reduced tongue weight is the leading cause of sway.

The second mistake is ignoring the rattle. The gap between a 2 in mount and a 2 in receiver is a manufacturing tolerance, not a defect, and an anti-rattle pin and shim removes it for the price of a coffee. People live with the clunk for years.