The Rise of Self-Driving Travel: Trailer Caravan Basics and Towing Guide

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Self-Driving Travel and Trailer Caravans

△ The Self-Driving Travel Boom
The rise of self-driving travel in China has led to a growing interest in this spontaneous travel style. They can grab their luggage and embark on a spontaneous journey at any time. To increase the carrying space for luggage and camping gear, many frequent self-driving owners install a towbar on the rear of their vehicles to tow a car or RV. However, drivers may not be aware that not all vehicles are suitable for towing a small trailer or RV.

In North America and Europe, trailers are widely used, and a wide variety of items are towed, including boats, horses, helicopters, cargo, and RVs. However, not all vehicles are suitable for towing with a towbar. Domestic users who lack automotive knowledge often fall into the misconception that any vehicle can be towed. In reality, this can cause serious damage to your car or SUV.

Vehicle Structure and Towing Principles
To better understand this, we need to briefly discuss the two common chassis structures used in passenger cars: monocoque and non-monocoque. The key difference between these two structures lies in the presence or absence of a chassis frame. Monocoque vehicles typically utilize a rigid frame, also known as a chassis frame. These vehicles typically employ a trapezoidal or rectangular chassis structure, which supports the entire vehicle, including the engine, suspension, and bodyshell. Because the steel frame provides strong rigidity, even uneven loads on the four wheels are handled by the chassis frame, ensuring vehicle safety. However, this high-strength structure also carries significant weight, making it primarily suitable for off-road vehicles or vehicles with heavy payloads.

Figure: Illustration of the classic chassis structure of a pickup truck or hardcore off-road vehicle. The body and chassis are designed as two separate components, tightly connected by dozens of bolts. However, for family vehicles, the heavy load of a monocoque is often unbearable, so most family cars on the market today use a monocoque design. Unfortunately, monocoques lack a chassis frame; the chassis and body are integrated into a single, unified structure. With this design, every vehicle component must be mounted on this frame. It not only bears the vehicle's weight but also withstands the stresses of components like the engine, transmission, and shock absorbers. It's particularly noteworthy that modern monocoque bodies utilize different steel strengths in different areas, aiming to ensure occupant safety through energy absorption and crumple mechanisms. However, this also reduces the overall frame rigidity compared to a non-monocoque body. Uneven force distribution between the wheels can easily cause the body to deform. Chassis reinforcement components have been developed to enhance frame rigidity and prevent this deformation.

△ Tow Hook Types and Selection
Next, we'll delve deeper into the two frame types. Most sedans and SUVs used for daily commuting utilize monocoque bodies. While these vehicles aren't incapable of towing, careful consideration must be given to the load being towed. For example, towing motorcycles or light loads weighing one or two hundred kilograms is feasible, a common practice in Europe and the United States. For these types of tow loads, the tow hook is typically mounted on the rear bumper. However, there are three different types of tow hooks on the market: universal, plug-and-play, and vehicle-specific.

Although universal tow hooks can be directly installed on the factory rear bumper, as mentioned above, the strength of a monocoque vehicle and the single function of the rear bumper limit their ability to handle high-intensity towing. Therefore, forcibly installing this type of tow hook to tow a heavy trailer can cause irreversible deformation of the vehicle frame over time. For those who prefer to use an SUV to tow a camping trailer, it is recommended to measure the six diagonal dimensions of your vehicle to ensure safe use.

Figure: Showing the base of a plug-and-play tow hook. Its square interface design accommodates most tow hook sizes. This type of tow hook is extremely convenient, but is primarily found on pickup trucks and SUVs with non-monocoque frames. These vehicles have pre-installed tow hook mounting holes at the factory, requiring the owner to simply purchase the appropriate tow hook for installation.

Specialized trailer hooks are designed for vehicles with monocoque bodies that lack a pre-installed tow hook opening. Installation requires removing the stock rear bumper, as a more robust one is already installed. These trailer hooks adhere strictly to the stock bumper's mounting position and dimensions to ensure a perfect fit. The thick, durable bumper replaces the stock rear bumper while easily supporting the weight of a towed cargo.

△ The Function and Misconceptions of the Rear Bumper
Although specialized trailer hooks and bumpers are tailored for monocoque bodies, it's important to note that these chassis designs weren't initially designed to anticipate the specific forces of towing cargo. Therefore, they may place some stress on the vehicle frame during use. For safety and vehicle integrity, a pickup truck or SUV is ideal for towing, if possible. After all, no one wants their vehicle to suffer irreversible damage due to improper use.

Finally, let's move on to towing. We often hear so-called "laboratories" make claims like, "Not having a rear impact beam is a downgrade" or "Not having a rear impact beam is a disregard for occupant safety." In reality, the primary function of a front impact beam is to protect pedestrians and vehicles. This is mandated by international automotive regulations and must be adhered to by all automakers. Therefore, front impact beams are typically made of deformable aluminum alloy. However, the question of whether they truly protect the vehicle and its occupants is less certain.

At ultra-low speeds, a front impact beam may be ineffective; at low speeds, it may offer some protection, but the effect is limited; and at medium and high speeds, it is virtually ineffective. What about a rear impact beam? This depends primarily on the vehicle's overall structure. For vehicles with unibody frames, a rear impact beam primarily reduces rear bumper repair costs in the event of a reverse collision with a wall. Beyond this function, however, it appears to offer no significant protective effect at other speeds. In particular, in rear-end collisions at medium and high speeds, the presence or absence of a rear impact beam does not significantly affect the performance.

However, there's a significant issue: in low-speed collisions, such as a 50% side impact, without a crash bar, only one side of the vehicle is deformed by pressure, making repair relatively simple. However, with a two-point connected crash beam, the problem can become much more complex. In this scenario, the entire rear frame, or even the entire vehicle, could be deformed (especially in structures with a through-the-vehicle auxiliary longitudinal beam), making repair of all six diagonal parameters nearly impossible.

Since rear crash beams are ineffective in high-speed rear-end collisions and can cause permanent damage in low-speed collisions, what's the point of them? Is it simply to prove that the manufacturer hasn't skimped on features? Or is it simply to satisfy the uninformed? Or is it a tool for certain media outlets to pry into the pockets of the manufacturer's marketing department?

Consistent with the purpose of this article, as rational drivers and car owners, we should have a clear understanding of which vehicles are suitable for towing, which parts have their intended functions, and which parts are merely cosmetic but lack practical effectiveness.