The wife and kids are as excited as you are about the new camper. You towed it home the five miles from the RV dealer, and everything seemed just fine. All the next week was spent stocking the shelves, filling the water and propane tanks, making the beds and stocking the fridge. The kids even slept in it overnight. Now, finally, it's time to hit the road. Which is almost literally true. The rear bumper of your van is nearly scraping the pavement. The steering is very light and unresponsive, because the front wheels are barely on the ground. And as soon as you get to the end of the freeway ramp, the whole trailer starts to do the rhumba back and forth, taking up all of your lane, three feet of the shoulder and three feet of the next lane. It's back to the drawing board, because your trailer wasn't rigged properly, or loaded appropriately.
Towing a trailer can be done safe and easily. Or at least it can when you have a properly matched vehicle/trailer combo, the proper hitch and the proper setup. Let's start with the basics: there are four major types of trailer hitches, regardless of whether they are installed at the factory (like many pickups and big SUVs) or added on afterward. A hitch may simply have a bar sticking out past the bumper with a ball mounted to it. Or there may be a square receiver that takes a ball mount that slides into it; there are several sizes of receiver hitches. Because of their versatility and the ease of removing that knee-knocker, they are the most popular. Many pickups simply have a reinforced hole in the bumper to take a ball. Another variation is the weight-distributing hitch, which simply plugs into a hitch receiver. Really large trailers use a 5th wheel or gooseneck hitch that mounts in the bed of a pickup truck.
In all cases, there are different weight ratings: it's a bad idea to tow a trailer with a hitch system that isn't rated for the weight of the trailer. The first consideration when specifying a hitch is the rating of your tow vehicle. There are three ratings you should be concerned about. The first, most obvious one is the Gross Towed Weight (GTW) of the trailer. Don't just copy that weight off of your trailer's title; you need to account for whatever is on or in the trailer as well. Think of the weight of any gear, cargo, propane tanks, gasoline in vehicles or boats, water in the freshwater, hot water tanks, and holding tanks, the beer in the refrigerator, the spare tire and any tools in a locker. Don't guess: get the bathroom scales out, weigh stuff, and keep written track; it's easy to add another 25% or more of the weight of an RV trailer and not realize it. A pair of snow machines or jet-skis will probably weigh just as much if not more than the trailer. The most accurate way is to actually weigh the trailer on a set of scales, but you need to make a good assessment of what you need before specifying the towing equipment you're installing. Don't underestimate. Truck stops, landscape supply places and stone yards will usually have scales; you don't need certified scales. Many establishments have scales that aren't certified and don't advertise them.
The second critical weight is the Tongue Weight (TW), the weight the trailer coupler puts on the hitch. Normally, this should be about 10-15% of the GTW. Any less is likely to leave you with a rig that sways uncontrollably behind the trailer. You can measure this the same day you weigh the trailer. Shift cargo around to get the tongue weight correct: you should never have less than 10%. See the sidebar for how to measure tongue weight with your bathroom scales, even if the tongue weighs considerably more than the 250-300 lbs your scales read up to. If you have a pickup truck and are carrying a substantial amount of weight in the bed (especially if it's back by the tailgate), you should consider it to be part of the tongue weight, reducing the amount of tongue weight from the trailer you can add.
The third critical weight is the Gross Vehicle Weight rating (GVWR). That's the maximum weight of the entire freight train rolling down the freeway: the tow vehicle, the trailer and the contents of the truck and trailer. Add up the cargo, fuel, water, groceries and people. It might very well be that the trailer is still comfortably inside the GTW while you've added enough cargo and people to the truck to exceed the GVWR. You can look up the maximum GTW, TW and GVWR weight for your vehicle in the owner's manual. You need to be sure that every component of the trailer hitch is up to the task. That's why the trailer industry has a classification system for trailer hitches that makes it simple to be sure the various components are all properly rated.
Sidebar on tongue weight with bathroom scales
Adjusting the tongue weight of your trailer is critical to good handling. It should be between 10% and 15% of the trailer's full-up weight. You can easily trim it by shifting cargo fore and aft on the trailer. You can easily check your tongue weight when you measure the weight of the laden trailer by simply moving the trailer forward a few feet on the scale platform until the trailer jack is on the ground, and weighing a second time; just subtract the second weight slip from the first. That's your tongue weight.
Setting tongue weight is critical enough that you should check it anytime the loadout of your trailer changes significantly. It's easy enough to do, just drop the tongue jack onto a scale, and read the weight directly. Is your trailer heavy enough that you have too much tongue weight for your bathroom scales? Try this: Be sure the trailer is on flat, level ground. Block both wheels on the trailer. Set the scale, and a piece of lumber the same thickness as the scale, three feet apart on either side of your trailer jack. Put a piece of pipe, round dowel or even a piece of angle iron, angle up, exactly three feet apart, centered on the wood and the scale. Now lay a piece of 4x4 across the top of the pipe/angle iron. Measure one foot across the 4x4 from the wood, two feet from the scale, and lay another piece of pipe right there.
Zero out the scale. Put the foot of your tongue on this pipe; you may need to remove the caster on the jack if you have one. Now multiply the reading on the scale by three for your tongue weight. This should let you set tongue weight for a trailer as heavy as 9,000 lbs. For an even heavier trailer, put the scale 4 feet from the wood and 3 feet from the tongue jack, and multiply by four instead of three.