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Ladder frame vs crossover

Not all SUVs are created equal

Updated

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Mitsubishi Montero Sport

Buying a new car can be a little confusing or even overwhelming when comparing cars to one another, especially when they’re priced similarly. This confusion is most apparent in the SUV / crossover segment, populated by subcompact crossovers, mid-sized pickup-based SUVs, full-sized SUVs, compact crossovers and more.

The biggest misconceptions, however, seem to be differences between crossover SUVs such as the Mazda CX-5, Honda CR-V, or Ford Explorer, and the pickup-based seven-seater SUVs such as the Toyota Fortuner, Mitsubishi Montero Sport, or Ford Everest. Although they all reside in the P1.6m – P2m range, they couldn’t be more different in terms of vehicle dynamics, and how they’re constructed.

For this comparison, let’s take the Honda CR-V SX AWD seven-seater with a diesel engine and Mitsubishi Montero Sport GT 2.4D AWD. With the CR-V priced at P2,125,000, and the Montero at P2,164,00, a mere P39,000 separates the two. At first glance, they appear to be extremely similar. Both are technically SUVs powered by diesel engines, both feature all-wheel-drive or four-wheel-drive systems, and both seat seven passengers. The main difference lies hidden beneath the shell of the car. The Honda CR-V features a monocoque / unibody chassis, while the Mitsubishi Montero Sport has a body-on-frame or ladder chassis. So which one is for you?

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A ladder frame chassis found under a traditional SUV’s body.

Body-on-Frame

Body-on-frame construction is one of the most reliable, tried and tested methods of constructing a vehicle. It consists of two components: a rigid, ladder-like frame that carries the engine and drivetrain (hence the term ladder chassis), and the vehicle body itself, which is mounted on top. We usually find this type of chassis on pickup trucks, where the rigid frame is better-suited to driving off-road or carrying heavy loads. As a result, modern seven-seater PPVs (Pickup-based Passenger Vehicles) such as the Toyota Fortuner, Mitsubishi Montero Sport, Isuzu Mu-X, Nissan Terra, and Ford Everest are basically SUV bodies placed on pickup frames (Toyota HiLux, Mitsubishi Strada, Isuzu D-Max, Nissan Navara, and Ford Ranger respectively). There are several advantages and disadvantages to SUVs built on a ladder frame.

Advantages

The super-tough construction of the ladder frame makes it the best choice for heavy towing and driving through rough roads and obstacles like large rocks or uneven surfaces. The body’s high torsional rigidity is able to resist a significant amount of force before bending. Since these vehicles also have higher floor pans due to their construction, their higher ground clearance also makes them better at wading high water levels.

Ladder frame vehicles are also easier to repair since the two main parts are isolated from one another. And since the ladder frame chassis has been around for over 100 years, it’s much easier for any mechanic to diagnose and repair any problems that may arise.

If you plan to drive the car in easily flooded or pothole-filled streets, rural areas such as farmlands, mountainous regions, or places where there are no roads, or if you plan carry heavy loads (either from passengers, gear, or towing), then a pickup-based SUV will better suit your needs.

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Honda CR-V

Monocoque / Unibody chassis

The unibody construction is much more modern, where the entire frame network is responsible for carrying the entire load of the vehicle’s components. This is done by strengthening the floor and pillars of the vehicle, combined with rigid bracing around various parts of the body. All modern sedans and hatchbacks use this method of construction, and SUVs and crossovers have begun to use this method of construction as well.

Advantages

Unibody frames are generally lighter, since the responsibility for carrying the vehicle’s load is spread throughout the frame. Since the overall load is lighter, smaller displacement engines can do the same job of a larger engine on a heavier ladder-frame vehicle. A smaller engine means a more fuel-efficient car.

Another advantage to being lighter is the ease of driving. Since these cars also have lower ground clearance measurements, the lower center of gravity results in more agile handling. Being lighter also means that the suspension system doesn’t have to be as rigid as they are on ladder-frame SUVs, which means a softer, more comfortable ride.

There’s a misconception that since ladder-frame SUVs have such rigid construction, this results in better protection during a major collision. However, how a car’s body behaves on impact relies on so much more than how tough the steel is. Monocoque bodies are designed to crumple and bend in very specific ways during a collision, ensuring that the impact force of the crash is diverted away from the vehicle’s occupants.

If you spend most of your driving time in the city, where your daily commute involves driving to and from the office on main roads, or bringing the kids to school and back, with the occasional trip to the beach on holidays, then you’ll enjoy a much more comfortable experience driving a crossover or SUV built with a monocoque/unibody chassis.

By Chris Van Hoven

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