Trailer Hitch Basics

There are a number of towing components to consider when determining whether a StowAway hitch cargo box will work with your vehicle. The following trailer hitch basics will guide you through the basic hitch and towing capabilities of a vehicle.

Trailer hitch receiver

Vehicle Hitch Tongue Weight Capacity

To determine which StowAway Cargo Carrier will work with your vehicle, the first trailer hitch basics point to consider is hitch Tongue Weight Capacity (TWC). What is tongue weight capacity? It refers to the maximum vertical weight that a vehicle's frame can support in a normal driving environment.

Shorter, lighter vehicles tend to have a lower TWC while larger, heavier vehicles tend to a have higher TWC. The best way to determine your vehicle's hitch Tongue Weight Capacity is to read your owner's manual. The owner's manual will provide detailed instructions and hitch tongue weight limitations, usually accompanied by tips for safe towing. Compare the owner's manual information with the certification plate on your driver's door sill.

A quick way to calculate hitch Tongue Weight Capacity is to multiply your vehicle's Gross Trailer Weight (GTWR) by 10% (tongue weight = GTWR x 10%).

Once you have identified your vehicle's TWC, subtract the weight of the carrier and frame to determine how much gear you can safely carry. For example, if you want to use a hitch bike rack and your vehicle has 1,500 lbs GTWR, then you have 150 lbs tongue capacity (1,500 x .10 = 150). If the weight of the bike rack is 40 lbs, you have 110 lbs leftover for the weight of your bikes.

Hitch Classes

Why do you need to know your Vehicle's Hitch Tongue Weight Capacity? Because it's an important factor in determining the receiver hitch class that different automobile manufacturers will install and recommend for use with their particular vehicles.

Trailer hitches are commonly divided into five classes. Each class is based on the strength and size of the vehicle it is intended to be used on. Hitches range from Class I (Light Duty Hitches) to Class V (Extra Heavy-Duty Hitches). The most common factory-installed hitch sizes on SUVs, vans and RVs are Class III (Heavy Duty) and Class IV (Heavy Duty). Many smaller SUVs come equipped with Class II (Medium Duty) hitches.

The following trailer hitch basics chart shows the hitch Tongue Weight Capacities that different hitch classes are designed to support.

Check your owner's manual or contact your dealer to confirm your factory-installed hitch’s class of trailer hitch ratings. If you're considering installing an aftermarket trailer hitch, please see the Installing a Hitch on Your Vehicle section below for more information.

Hitch Class Tongue Weight Capacity* Towing Capacity*
Class I 200 lbs 2,000 lbs
Class II 250-350 lbs 3,500 lbs
Class III 350-500 lbs 7,500 lbs
Class IV 500+ lbs 10,000 lbs

*Approximation: Depends upon vehicle.

Hitch Sizes

Hitches are sometimes identified by size rather than class. Hitch sizes refer to the inside diameter of a vehicle's hitch receiver opening. Class III and Class IV hitches have a diameter of 2 inches, thus they are often referred to as "2 inch receivers." Class I and Class II hitches generally have a diameter of 1.25 inches, thus they are often referred to as "1.25 inch receivers."

Note: Some manufacturers fabricate Class I and II hitches with a 2 inch hitch opening to accommodate a greater range of hitch accessories, so do not assume that a 2 inch opening equates to a Class III or Class IV receiver hitch.

Larger receiver openings will generally have greater hitch Tongue Weight Capacities and smaller receiver openings will generally have smaller ones. Check your owner's manual, contact your dealer, or simply measure your receiver opening's diameter to determine your hitch size.

StowAway Hitch Compatibility

Every StowAway Cargo Carrier and cargo rack slides directly into the hitch receiver that is mounted to your vehicle. Our carriers are designed for use with Class II (1.25 inch), III (2 inch) and IV (2 inch) hitches.

Refer to the trailer hitch basics chart below to see if your hitch receiver is compatible with one of our StowAway cargo carriers.

StowAway Products Class II (1.25") Class III (2") Class IV (2")
MAX Cargo Carrier X X
Standard Cargo Carrier X X X
Hitch Cargo Racks X X X

Hitch Converters

Hitch Converters are hitch accessory products designed to change the size of your hitch receiver opening. The most common Hitch Converter used with SUVs, vans, and RVs is the 1.25 to 2 inch Hitch Expander. Hitch Expanders enlarge your hitch receiver opening from the smaller 1.25 inch opening to the larger 2 inch opening.

Note: Using a Hitch Expander does not change the hitch's class rating or Tongue Weight Capacity, it only changes the size of the receiver opening. For this reason, we do not recommend using a 1.25 to 2 inch Hitch Expander with any of our StowAway Cargo Carriers. Attempting to use such a converter with one of our carriers could place undue stress on your vehicle's frame and/or hitch.

Another common Hitch Converter is the 2 to 1.25 inch Hitch Reducer. This converter is the opposite of the Hitch Expander, as it shrinks the larger 2 inch opening to the smaller 1.25 inch opening. A Hitch Reducer will allow you to safely use one of our 1.25 inch hitch models on a vehicle with a 2 inch hitch receiver opening.

Hitch Extenders

Hitch Extenders are a hitch accessory that increases the distance between the back end of your vehicle and the hitch receiver opening. They are often used to accommodate rear-mounted spare tires and ladders, or to increase the turning clearance of a towed vehicle.

Due to the weight of our StowAway Cargo Carriers and cargo racks, we only recommend using a Hitch Extender on a Class 3 or above (2 inch) hitch. We also recommend the use of a Hitch Tightener to secure the junction between the Hitch Extender and the hitch, as well as the carrier's frame and the Hitch Extender. This is the best way to eliminate hitch wobble or rattle.

Note: We do not recommend using a Hitch Extender on a 1.25 inch trailer hitch, or a Hitch Extender longer than 7 inches (measure from hitch pin hole to hitch pin hole on the Extender).

Also note that the use of a Hitch Extender in conjunction with a StowAway Cargo Carrier decreases the carrying capacity of the StowAway by 1/3. Therefore, you should limit the weight of your gear to roughly 130 lbs when you use your StowAway Cargo Carrier with an Extender.

Installing a Hitch on Your Vehicle

If you intend to purchase an aftermarket trailer hitch, be sure to take into account your vehicle's Tongue Weight Capacity (TWC). It is important to avoid purchasing and using a hitch that is designed for a heavier duty vehicle than the one you plan to use it with.

A common misconception is that by placing a Class III or IV (2 inch) hitch on a lighter-duty SUV or even a car, the vehicle will be able to support the TWC that these heavier-duty hitches are designed to support. This is an incorrect assumption that could very easily place undue stress on your vehicle's frame and/or hitch if you were to max out your hitch's TWC. Your vehicle's TWC will not increase when you install a hitch, even if the hitch is designed to support a weight greater than your vehicle's max tongue weight capacity.

The following trailer hitch basics chart contains some rough guidelines to follow when purchasing an aftermarket trailer hitch.

Vehicle TWC Recommended Hitch Class*
200-300 lbs Class II (1.25" Hitch)
300-500 lbs Class III or IV (2" Hitch)
Over 500 lbs Class IV (2" Hitch)

*Approximation: Depends upon vehicle.

Additional Questions?

For additional questions or concerns on trailer hitch basics, feel free to contact one of our cargo carrier specialists via email or phone, toll-free at 800-943-5377.