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You probably don’t think all that much about what’s going on underneath your car. The things you can see, hear, and feel, such as the interior, tires, brakes, engine, exhaust, and lighting system, are typically much closer to top-of-mind, but they’re far from the only important parts of your ride.
In fact, the car’s chassis forms the foundation for every other component it carries. The fuzzy dice you love so much (don’t lie), the seats, body, and everything else all ride on the chassis. The type, size, and shape of the chassis will vary from vehicle to vehicle and manufacturer to manufacturer, but the basics are roughly the same.
Why is the chassis so important? Well, besides forming the base for literally everything, the chassis plays a part in determining towing capabilities, payload ratings, and can make or break a vehicle’s ability to handle and perform well in a variety of situations. The Drive’s editors have seen a handful of bare chassis and spoken to many an engineer over the years, so
Let’s take a closer look.
What Is a Chassis and What Does it Do?
The chassis, or frame, forms the basis for the rest of the vehicle. Everything else is built on the chassis. You may see other components included in the term, such as suspension, brakes, and others but for this post, we’re going to focus only on the frame itself.
Modern vehicles typically have one of two different styles of chassis: Unibody or body-on-frame. Unless you drive a pickup truck or large SUV, there’s a great chance that your vehicle has a unibody chassis. This means that the body––the thing that gives the car its exterior shape––and the chassis or frame are all part of the same assembly. Unibody designs help save weight and provide a smoother ride. They can also prove beneficial in crash safety and reduce production costs if they can be adapted for other vehicles in a manufacturer’s lineup.
Vehicles with body-on-frame construction are, as they sound, constructed from a frame with the body attached on top. Trucks, SUVs, and off-road vehicles still use this setup because it allows for better flexibility, ground clearance, and can withstand heavier loads.
How Is a Chassis Made?
Depending on the vehicle and its purpose, the chassis can be made from materials such as carbon steel, aluminum, or even carbon fiber. The weight, rigidity, and costs all play a part in how and why a material is selected for use in a chassis, too.
Carbon fiber is extremely lightweight and rigid, but is too expensive to be used in all but the most focused applications. The construction process also depends heavily on the material, as mainstream metals like aluminum or steel can be rolled and welded in a production line setting, but specialty materials like carbon fiber may require complex hand-molding and construction.
How Does Chassis Structure Affect Handling?
Handling begins with a car’s chassis. Tires, brakes, and suspension can only do so much to tame a soft chassis. Chassis flex when a car is cornering or accelerating can cause instability and reduce tire grip as the alignment and toe change. This is all wrapped up in something called torsional rigidity, which refers to the chassis’ resistance to twisting.
Rather than just being stiff, a rigid chassis that resists torsion provides a better ride and sharper handling, because it allows the suspension and tires to do their jobs. This is why convertibles aren’t typically the best handlers, since there’s no roof to tighten up the chassis and prevent twisting. Those that have been prepped for better handling usually have added material and weight in the floor, or are made from exotic materials like carbon fiber to improve rigidity.
What You Want From a Good Chassis
Different types of vehicles demand different types of chassis designs. The Toyota Corolla sitting in your driveway is vastly different from your neighbor’s Jeep Wrangler underneath. Here’s why.
Consumer Road Cars
Consumer road cars’ chassis design is engineered to provide a safe, smooth ride with as little unwanted noise as is possible. That’s why most cars today use a unibody chassis design, which has lightness for better fuel economy, better energy absorption in a crash for safety, and better ride/handling for comfort.
Off-road vehicles require a chassis that is strong and easy to repair. The forces exerted on a vehicle as it climbs over rocks and hits tough terrain can be extreme, so many off-roaders use a ladder-style body-on-frame chassis to provide the toughness and longevity needed to stand up to years of abuse.
Track and sports cars need a stiff, light chassis that allows for the engine and other heavy components to be mounted low. This gives the vehicle a lower center of gravity and better handling. This is a little different from typical consumer road cars, in that interior space and comfort aren’t necessarily at the top of the list of priorities.
Do Electric Vehicles Have a Chassis?
Yes, but you may hear them being called different things.
Sometimes, EVs’ chassis are called “skateboards,” because they are literally a long, low structure with four wheels, upon which the rest of the vehicle is built. The skateboard houses the batteries and the motors are located in or near the wheels, so it does actually look like the thing Tony Hawk rode to fame and fortune.
This is big for automakers because the skateboard can be modified to work with a variety of vehicles and vehicle types, making it cheaper and more efficient to create a wide array of EVs.
Is There a Difference Between a Chassis and a Platform?
It really depends on who you’re asking. Automakers use the term platform to describe a collection of components and features that can be shared between vehicles. Think about General Motors, with the Chevrolet Suburban, Cadillac Escalade, and GMC Yukon all riding on the same basic setup, but with different bodies and interiors. In these cases, the chassis is included in the platform umbrella term.
Chassis-Related Terms You Should Know
A vehicle’s drivetrain is a collection of components that includes the engine, transmission, differentials, axles, driveshafts, and more. You might hear the term used to describe just the engine or the engine and transmission together, but there’s a lot more going on than just those two parts, no matter how big or important they are. This term also includes EVs.
Gross Vehicle Weight Rating
The gross vehicle weight rating, or GVWR, is a measure of the total operating weight that a vehicle can carry at any given point in time. It’s important to note that the GVWR includes passengers, fuel, cargo, and the vehicle itself.
Towing capacity is a measure of the total weight that a vehicle is capable of towing behind it. It’s determined by taking several factors into account, including the GVWR.
The payload capacity is the maximum amount of weight that a vehicle can safely carry in its cargo area. It’s calculated by taking the GVWR and subtracting the vehicle’s curb weight.
FAQs About Car Chassis
You’ve got questions, The Drive has answers!
Q: Can a Chassis Be Repaired If It’s Damaged?
A: The degree to which a frame or chassis can be repaired depends completely on the level of damage it sustained. If it was slightly bent but not to the point it has been structurally weakened, there’s a good chance it can be fixed. However, if the frame has been bent or twisted in a way that compromises its integrity, you should consider moving on.
Q: Do Any Trucks Use a Unibody Design?
A: The only truck on sale right now with a unibody chassis is the Honda Ridgeline. That may change with a few compact pickups that will come to market in the next few years, but the Honda is today’s only unibody truck.
Q: Can I Tow With My Sedan?
A: Yes, you certainly can tow with a regular old car, but you’ll need to be acutely aware of the trailer’s weight and the car’s capacities. You won’t be pulling a horse trailer with your Camry anytime soon, but you should be able to tow a small pop-up camper or moving trailer from U-Haul with no trouble at all.
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