You just bought a used pickup, complete with a hitch receiver and a tow ball already installed, leftovers from the previous owner. The wiring and the brake controller are already in place too. The used-car dealer assures you that the truck is more than capable of towing your new 6,000-lb. toy hauler, no problem.
Saturday morning, you zip over to the trailer dealership to pick up the trailer. But the manager at the trailer dealer informs you the ball mount and ball on your truck aren't suitable: you need a larger-diameter 2 5/16" ball instead of the 2" ball you showed up with. There's more: the ball mount and ball you have is only rated for a Class II trailer, less than 3.500 lbs. The trailer tongue is 5" below the ball, so you'll need a ball mount with 5" of drop, a bigger ball, and both of those need to be rated for Class IV duty. It's worse: He strongly recommends a weight-distributing hitch to transfer some tongue weight, whatever that is, to the front wheels. Wasn't this truck supposed to be up to this? By the time you actually have your trailer home, you've spent nearly a thousand dollars and spent most of the day you intended to spend traveling cooling your heels in the waiting room waiting for the installation. Obviously, this towing business has more to it than meets the eye.
When you're setting up your trailer with a new tow vehicle, several things need to be considered: the ball mount and ball must be rated to take the weight, and the ball has to be at the right height. You've already installed a hitch receiver of the appropriate weight class for the largest trailer you ever intend to tow, right? Let's say your small camper weighs 2300 lbs empty. You can add 700 lbs. of gear and still use a Class II hitch, which is okay for trailers up to 3,000 lbs. Adding 800 lbs. of payload to a camper is surprisingly easy to do, once you remember that water weighs 8 1/3 lb. per gallon. 30 gallons of water in the freshwater tank is a quick 250 lbs. It would be pretty easy to add enough camping gear, clothing, bicycles and food to go over the 3,000 lb. max for a Class II Hitch. ) Don't paint yourself into a corner and underspecify the class of towing equipment you'll need.
Most vehicles that are used to tow more than 3,000 lbs will benefit from the use of a weight-distributing hitch; some will require it. Weight-distributing hitches are discussed in another article.
You've determined that a Class II hitch is needed, and your vehicle is (1) rated to tow a 3,000-lb trailer, and (2) rated to have as much as 450 lbs of tongue weight. Odds are you'll only need 10% of the weight of the trailer on the tongue for good towing, but if you have a car that only will support 250 lbs. of tongue weight safely, you'll need to upgrade to a weight-distributing hitch. Similarly, the heavier your trailer is, the higher a weight class your hitch assembly has to meet.
Ball Mounts are a key product in the towing industry and a core item within the CURT product line. CURT ball mounts are a step above the rest. We've invested in the technology necessary to produce a full line of exceptionally strong and attractive ball mounts. The vast majority of our line is CNC formed and robotically welded to ensure accurate, consistent cuts and clean, strong weld lines. Once welded, these mounts undergo a process that creates a flawless surface for the application of our highly durable CURT powder coat finish.
How to calculate your ball mount drop
A: Distance from ground to top of inside diameter of receiver tube opening
B: Distance from ground to bottom of trailer coupler
C: Drop or rise needed
Measuring your ball mount
C: Hole Size
Once you have determined the proper weight class, here's how to set up your ball mount and ball for proper towing. Park your trailer and tow vehicle on flat, level ground. The trailer will tow best when it's level to the pavement: with the trailer jack, a floor jack or even some wooden blocks, level the trailer. Just lay a carpenter's level on the tongue and move the tongue up and down until the bubble centers. Measure the distance from the bottom of the tow vehicles' receiver opening to the ground. Next, measure from the bottom of the trailer coupler to the ground. If those dimensions are the same, you need a ball mount with 2" of drop. If the receiver is higher than the coupler (which it probably is if you're towing with a truck, you need a ball mount with more drop. If the coupler is higher, (which it could conceivably be if you're towing with a car), you'll need some rise: just turn the ball mount upside down. Choose a ball mount of a high enough class for your trailer.
The last thing to spec out is the ball. Start by eliminating everything with a lower weight class than yours. You know the ball diameter: it has to match the coupler on the trailer. The ball mount mounting hole is probably ?" or 1", maybe larger if your trailer is Class 4 or 5. The shank of the ball must be the same diameter, and long enough so that two full threads are visible when the nut is torqued down. If you must, there are bushings to step up the shank diameter to the next size, but its' best to use a shank that fits the hole properly. You'll need a very big pair of wrenches to tighten the nut, which may require as much as 450 ft.-lbs. for a 1" shank. Pipe wrenches are not suitable. A socket or at the very least a big crescent wrench will be needed. The correct torque will be somewhere in the package with the ball. Tighten the nut by putting the ball mount in the receiver sideways, so you can put your full weight on the end of the wrench. Check the torque of all the bolts on your hitch after the first 20 miles, and then at least daily. On long tows, check at every fuel stop.
Remember: the rating of your hitch/ball mount/ball/coupler is only as good as the lowest-rated component in the system.