Can a Unibody Vehicle Frame Safely Carry a Hitch-Mounted Carrier?

The frame or chassis of your vehicle is critical in determining if it can safely transport a hitch-mounted carrier, as well as determining just how much weight can be supported by the hitch.

Vehicle frames have taken many shapes over the years as engineers build better chassis designed to be lighter, stronger, and better suited for specific vehicle applications. Body-on-frame designs were the gold standard, however unibody frames are becoming more and more popular. Although they have some advantages over body-on-frame designs, unibody’s present some challenges when it comes to carrying weight directly on their hitch.

What is a Unibody Vehicle Frame?

Unlike vehicles where the chassis and body are separate entities, unibody (or unitized body) refers to a chassis and body that are integrated into one structure; sort of like a tortoise shell. Unibody chassis attach to each vehicle axle independantly, unlike a traditional vehicle chassis. With modern manufacturing technology, this design allows for lighter overall vehicle weights, and therefore better fuel efficiency, and it tends to ride better than a vehicle with a separate body and frame (also known as body-on-frame construction).

Unibodies are manufactured in a combination of several ways: by welding preformed metal panels and parts together, by casting sections as one piece, or both. Because the final product is a fully-integrated structure, the entire vehicle is load bearing instead of just the chassis.

Unibody design is now common in many mass-market cars and crossovers because it lessens the overall weight, is easier to manufacture, and is better for spacing and layout. Additionally, the integrated body design means better protection for driver and passengers in the event of an accident.

A century in the making

The 1922 Lacia Lambda was the first car to attempt an integrated chassis design, followed by the Budd Company in America, who provided pressed-steel bodywork to Dodge, Ford, Buick and Citroen for many years. It wasn’t until 1930 that Budd produced a complete unitary prototype and sold it to Citroen. Citroen mass-produced it for over 23 years as a low-sitting vehicle with a flat-floored interior known as the Traction Avant.

How do Unibody Frames Handle Hitch-Mounted Carriers?

The short answer is that they are not designed to support much weight on their hitch. Although many unibody vehicles are capable of towing trailers, and support a trailer tongue weight, their hitches are not located in a favorable position to handle the larger downward forces created when transported a hitch-mounted carrier. Even their towing capacity is greatly reduced compared to similar body-on-frame vehicles.

Body-on-Frame vs Unibody: 2021 Ford Bronco vs Ford Bronco Sport

A great example of the difference the chassis makes is with the 2021 Ford Bronco and Ford Bronco Sport, both in terms of how we look at towing tongue and hauling tongue capacity.

The 2021 Ford Bronco has a towing capacity of 3,500 lbs. with the standard 2.3L EcoBoost engine and upgraded Class II Trailer Tow Package. The towing tongue capacity? About 300 lbs. The tongue hauling capacity? That will depend on the condition of the vehicle itself.

The 2022 Ford Bronco Sport has a maximum towing capacity of around 2,200 lb. with an upgraded 2L EcoBoost engine and Class II Trailer Tow Package. The towing tongue weight capacity? About 200 lbs. The tongue hauling capacity? 0 pounds, due to the unibody design.