How to Measure the Size of a Hitch Ballby David Thompson
Hitch balls connecting trailers to vehicles come in three standard diameters. To make sure a ball fits, you also need to measure its shank diameter and length. Larger balls with larger-diameter shanks can pull more weight. Manufacturers divide hitches into different classes, but in general, 1 7/8-inch-diameter balls with smaller shanks can pull up to 2,000 lbs. Two-inch balls may be rated for pulling up to 3,500 or 5,000 lbs. depending on the shank size. Choose a hitch rated for the amount of weight you plan to pull that matches the size of the trailer's coupler.
Hold a ruler horizontally on top of the hitch ball and sight down directly from above. Align the first mark of the ruler with the widest part of the ball on one side and note where the other side of the ball is aligned. The ball should measure either 1 7/8, 2, or 2 5/16 inches.
Lay the threaded part of the ball's shank on the ruler and sight down to measure the shank's diameter. The shank is the bolt-like shaft that extends below the ball. Its diameter will probably be 5/8, 3/4, 1, 1 1/4 or 1 3/8 inch.
Measure the length of the shank, starting just below the wide base supporting the ball and measuring to the end. The length doesn't affect towing capacity, but it needs to be long enough to fit your mounting platform.
- If you have trouble sighting down 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 itself, unwrap it and measure it. Divide the measurement by 3.14 to calculate the diameter and round it to one of the three standard diameters.
- The hole in the mounting platform for the ball's shank should be no more than 1/16 larger than the shank, according to Hitch House USA's Towing Tips.
- Check the manuals of both the trailer and your vehicle for information on fitting the hitch, towing capacity, necessary equipment and safety advice.
- Hitch balls also come in high rise and regular height. High rise balls have a longer base, placing the ball higher above the mounting platform. Choose a high rise ball if you need additional height to level a trailer whose coupler is higher than the vehicle's hitch.
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David Thompson began writing for eHow in 2009. He has written how-to articles on home improvement, carpentry, cabinet making and gardening.