by David Thompson
camping, trailer image by Greg Pickens from Fotolia.com
The hitch balls that connect trailers to vehicles come in three standard diameters. To make sure a ball will fit, you should also measure the diameter and length of its stem. Larger balls with larger diameter shanks can pull more weight. Manufacturers divide hitches into different classes, but generally 1 7/8 inch diameter balls with smaller shanks can lift up to 2,000 pounds. The two-inch balls can be rated to pull up to 3,500 or 5,000 pounds. depending on the size of the reed. Choose a hitch rated for the amount of weight you plan to pull that matches the size of the trailer hitch.
Hold a ruler horizontally over the hitch ball and look directly from above. Line up the first mark on the ruler with the widest part of the ball on one side and note where the other side of the ball is lined up. The ball should measure 1 7/8, 2, or 2 5/16 inches.
Place the threaded portion of the ball stem on the ruler and look down to measure the stem diameter. The stem is the bolt-shaped shaft that extends under the ball. Its diameter will probably be 5/8, 3/4, 1, 1 1/4, or 1 3/8 of an inch.
Measure the length of the stem, starting just below the wide base that holds the ball and measuring all the way to the end. The length does not affect the towing capacity, but it should be long enough to accommodate your mounting platform.
- If you have trouble seeing the ball to measure the diameter, cut a strip of paper about 1/2 inch wide and wrap it around the widest part of the ball. Mark where it overlaps, unwrap and measure. Divide the measurement by 3.14 to calculate the diameter and round to one of the three standard diameters.
- The hole in the mounting platform for the ball stem should be no more than 1/16 larger than the stem, per Hitch House USA towing advice.
- Consult both your trailer and vehicle manuals for hitch mounting information, towing capacity, necessary equipment, and safety tips.
- Hitch balls also come in high rise and regular height. High-rise balls have a longer base, placing the ball higher than the mounting platform. Choose a high-rise ball if you need extra height to level a trailer whose coupler is higher than the vehicle hitch.