Checking out a vehicle manufacturer's ratings can help you choose which hitch works best for you. Automotive manufacturer's tow-rating requirements will often list certain types of hitches. Usually, the requirements will be for either "deadweight", "frame mounted", or "weight distributing". Also, manufacturers do not recommend towing with some vehicles.

Note: Even though a vehicle has a manufacturer rating for a certain towing capacity, certain states may require special vehicle features and components to be installed, on the vehicle, to tow trailers that would exceed state permissible weight and length limits.

It's just common sense, you can tow a lighter load with a heavier hitch, but you can't safely tow a heavier load with a lighter hitch. Before making a hitch selection,  you need to know your total towed load.

HITCH CLASSIFICATIONS
Four basic classifications are given to conventional hitches: Class I (up to 2000 pounds). Class II (2000 to 3500 pounds), Class III (3500 to 5000 pounds) and Class IV (5000 to 10,000 pounds). Hitch makers have also begun to use the designation of Class V to indicate a heavier-duty hitch especially designed for those owners who do not want or need to use a weight-distributing hitch.
Most hitches are considered to be weight-carrying (also called "deadweight"), which means they support all of the trailer tongue weight. They are the most popular hitches and are used to tow light or medium loads. Hitches are rated for Gross Trail Weight (GTW) and tongue weight (TW). Many Class III and Class IV hitches have weight-distributing capabilities, which means they can be used to distribute tongue weight to the front of the tow vehicle and to the trailer to relieve overweight conditions at the rear of the tow vehicle.

CLASS I HITCHES
The smallest hitch is a Class I, and is intended for loads less than 2000 pounds. It comes in three basic types: a bumper mount, a bumper-frame mount, and as part of a step bumper.
A bumper-mounted hitch is not recommended by most automotive manufacturers.

Today's car bumpers are generally made of a light alloy or aluminum, while hitches are made of steel. Besides not having sufficient strength, modern bumpers can cause a galvanic action between the alloy and the steel hitch, which can lead to corrosion and eventual failure. In addition, depending on the way it installs; a bumper hitch can create an in-and-out action when towing that upsets modern impact bumpers, which not only affects tow ability but can damage the bumper's energy-absorbing system. If using a Class I bumper hitch, it is best to get one that also bolts to the frame or chassis of the vehicle.
Step-bumper hitches, found on trucks, don't always have tow ratings. Some are for decorative purposes only. Even though a step bumper may have a hole drilled into it for hitch ball installation, the bumper itself may not be strong enough to handle a bouncing tongue load. If you choose a step bumper, be sure it is properly constructed for towing and that it has a tow rating stamped into the metal. Some automotive and aftermarket manufacturers offer step bumpers with high tow ratings.

CLASS II HITCHES
Class II hitches are frame-mounted, which means they connect to the frame or structural cross members of the vehicle, not to the bumper. They are rated to tow up to 3500 pounds.  Some vehicles may need extra bracing to help support this hitch. On a uni-

body vehicle, for example, the hitch is bolted to sheetmetal rather than to a heavy-gauge steel frame. Without extra support, the bolts can pull away from the sheetmetal. Factory installed hitches usually have an extra metal plate for support when the tow package is ordered, as do competent hitch manufacturers.
There are a few variations regarding Class II hitches. One has a ball-mounted permanently built into the hitch assembly. Some use a receiver, which has a removable ball-mount that fits into a square hole. Receiver hitches come in two ball-mount sizes. On a receiver hitch, the ballmount is the shank that holds the hitch ball and fits into the receiver. This ball-mount shank can be either 1 5/8 or 2 inches square. The smaller shank size is used with a mini-hitch, which has a tow rating limited to 3500 pounds. The smaller mini-hitch allows better ground clearance and is more easily hidden under the vehicle than a full-size hitch.

CLASS III AND IV HITCHES
Class III (up to 5000 pounds) and Class IV (up to 10,000 pounds) hitches are necessary for heavy-duty towing. This is a weight category for which you will probably need a truck and a frame-mounted receiver hitch. More important is that

you'll be getting into very heavy tongue weights that can affect the way your vehicle tows.  Although a 500-pound tongue weight may not sound like a lot of weight, that weight takes on a different perspective when it's pushing down on a hitch ball that might be six feet behind the rear axle. This creates a six-foot-long lever that lifts the front steering wheels of the tow vehicle, drops the front of the trailer and results in sloppy steering. a thumping bounce at the back of the tow vehicle, and sway at the back of the vehicle and at the trailer. Suspension aids may help some, but the most successful counteraction to this leverage action is the use of a weight-distributing hitch.

CLASS V HITCHES
These are large, heavy-gauge steel hitches designed for large trucks with high tow ratings. Their primary purpose is to allow towing without having to use a weight-distributing hitch. Class V hitches are often referred to as "deadweight hitches."

WEIGHT-DISTRIBUTING SYSTEMS
A weight-distributing or load-equalizing system spreads tongue weight over the front and rear axles of the tow vehicle and the trailer axle(s). With a 500-pound tongue weight, for example, you can redistribute the weight so that 200 pounds of that weight is on the front axle, 200 on the rear axle and 100 on the trailer axle(s). The result is a stable, controllable tow vehicle and trailer.
The weight-distributing system consists of a frame-mounted platform and spring bars (also called equalizing bars) that attach to a special ball-mount assembly and to the trailer frame. With the spring bars in place, they act like handles on a wheelbarrow. As the wheelbarrow handles are raised, the weight is shifted forward on the wheelbarrow. This same leverage principle applies when the spring bars (wheelbarrow handles) are raised and secured to the trailer.
A special ball-mount is also needed, because it mates with the receiver and furnishes sockets into which the spring bars are inserted. The weight-distributing ballmount is also adjustable. It is especially important to set the hitchball angle and to raise or lower the hitchball to properly set spring-bar height.
Two spring bars are used-one on each side of the ballmount. The bars have chains connected at the trailer end, which attach to snap-up brackets on the trailer tongue. The length of the chains actually distribute the tongue weight as they are raised to put tension on the spring bars. In turn, each bar acts as a spring to maintain a constant pressure on the hitch.  Spring bars have different tensions built into them. So, when you want to tow a 3000, 5000, or 7000 pound trailer, be sure you get matching spring bars to handle the job.

Note:  This is a weight-distributing system, rather than a weight-distributing hitch. Many Class III and most Class IV hitches can be used with a weight distributing system. Always check with the manufacturer of the hitch when attempting to use a weight-distributing system. Also note that some boat trailer manufacturers have limitations on the use of   weight-distributing systems. Contact your servicing dealer.

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