RV Ball Mounts & Hitch Balls

Sizing a ball mount and hitch ball

Four numbers decide whether a ball mount and ball are right: ball diameter, drop (or rise), shank size, and weight rating. Miss any one and you either can't latch the coupler, tow nose-high or nose-low, or overload the hardware. Here's what each does.

• Ball diameter. This has to match the trailer coupler stamped size — commonly 2" or 2-5/16". A 2" coupler will not lock onto a 2-5/16" ball, and forcing a mismatch is how trailers come off. Read the coupler stamp and match it exactly.
• Drop or rise. The drop sets tow height. You want the loaded trailer riding level, so measure from the receiver to the coupler and pick a drop that closes the gap. A 4" drop mount, flipped, becomes a rise for taller trailers.
• Shank size. The shank must match your receiver opening — 1-1/4" for Class I/II, 2" for Class III and up. A reducer sleeve, like the Buyers 2-1/2" to 2" adapter, lets a smaller shank run in a bigger receiver.
• Weight rating (GTW). The ball and mount each carry a gross trailer weight rating; use the lower of the two and stay under it. A 2" ball rated 10,000 lb and a 30,000 lb 2-5/16" ball are not interchangeable just because one costs less.

Once the ball's on, the trailer coupler still has to latch and lock, which is the job of the couplers and locks page. If you're pulling a heavier travel trailer, a plain ball mount may not be enough — look at the weight-distribution hitches to level and control sway.