How to pick the proper trailer hitch and towing vehicle for any size job.
Pulling a trailer is not as easy as it seems, especially if you want to do it safely. Many contractors simply connect a trailer to their car or truck, hook the tow chains to the hitch, plug in the lighting connector and drive off. In most cases, little thought is put into towing, until the trailer sways—or something worse happens.
Selecting the proper tow vehicle and trailer hitch is probably the most important part of trailer safety. You might argue that selecting the right trailer component is equally important, and it is, except in most cases, the trailer manufacturer has already selected the right components based on the load ratings or mobile equipment specifications. The trailer operators only have to worry about loading the trailer with proper balance and weight restrictions and hooking it to the tow vehicle.
Tips on Purchasing a Hitch
Various types of hitches are available for tow vehicles. It is usually best to purchase the largest available hitch from the vehicle manufacturer. The most capable hitch will usually come from the vehicle manufacturer as a “tow package” that generally includes special axle ratios and weight ratings, larger engine cooling packages and increased electrical systems and wiring.
When you hitch the trailer to the tow vehicle, the ride height of the tow vehicle should remain essentially the same before and after the connection of the trailer. Excessive trailer sway may occur if the ride height is reduced or increased by a couple of inches. Reducing the ride height reduces the weight on the tow vehicle’s front axle and may cause erratic steering. Conversely, increasing the ride height will increase the weight on the rear axle of a tandem axle trailer and may cause erratic trailer braking. Adjusting the hitch height of the trailer coupler in many cases will allow the ride height to be corrected. Otherwise, the tow vehicle’s suspension will need to be corrected, or the use of a weight-distributing hitch may need to be considered.
Hitches are generally classified by weight and capability:
ClassTow Rating in Pounds Tongue Weight in Pounds
I 2,000 200
II 3,500 300
III 5,000 500
IV 10,000 1,000
V Custom Engineered Custom Engineered
The ratings shown in the chart above are typical. Some variations may be found from manufacturer to manufacturer. In most cases, Class V hitches are considered fifth wheel, although some manufacturers will claim a bumper pull Class V in the range of 12,000/1,200 pounds. Notice that the maximum tongue weight is approximately 10 percent of the tow rating in most cases. For good trailer balance, the tongue weight is typically set to around 15 percent of the GVWR of the trailer and generator. In the case of towable generators, expect the maximum tongue weight to be critical in sizing the proper vehicle.
For example, if you use a Class IV hitch (as shown in the chart on page 42) and a mobile generator with a 15 percent tongue weight, the maximum GVWR of the generator cannot exceed 6,600 pounds. A fully-fueled 130kVA, TS130T mobile generator weighs about 6,850 pounds.
Also, notice that in the TS250T and TS400T examples, a custom engineered trailer hitch would be needed.
Large mobile generators need special attention when selecting the proper tow vehicle. Exceeding the tow vehicles ratings as stated by the manufacturer is not recommended. Check your local laws and regulations to ensure compliance based on vehicle size and licensing requirements.
Vehicle Tow Ratings
“Trailer Life” magazine provides a yearly guide on vehicle tow ratings, which lists all the popular vehicles by vehicle model year. The guide is also posted on their website, www.trailerlife.com, and it contains archived guides dating back seven or eight years.
So what’s the largest towing capacity of a pickup style truck? According to the 2009 Trailer Life Guide, a Toyota Tundra has a rating as high as 10,800 pounds, the Ford F-350 has a tow rating as high as 15,000 pounds, the Chevrolet/GMC 3500 has a tow rating as high as 16,800 pounds, while the Dodge Ram 3500 shows a tow rating up to 16,850 pounds. All of these ratings are for conventional bumper pull trailers. The tow ratings are generally higher for fifth-wheel trailers.
How Big Is That TS Mobile Generator?
Typically, a 250kVA, TS250T mobile generator weighs 8,900 pounds without fuel. Before attempting to tow a generator this large, check your truck’s tow ratings and the rear axle rating and hitch ratings to ensure safe towing.
Consider that a 500kVA, TS500T mobile generator weighs 15,420 pounds without fuel. But are you really going to pull a generator to a jobsite without any fuel in it? By the time you fill up the 530-gallon fuel tank, you add 3,763 pounds to the base weight of 15,420 pounds to bring the total GVWR (see page 45 for an explanation of GVWR) of the TS400T generator to 19,183 pounds. If you are towing in a state that requires a CDL to pull a trailer as large as these mobile generators, make sure you are properly licensed and insured.
Construction Business Owner, February 2011
