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What Is a Subframe?

Modern subframes make cars safer by helping to absorb energy during a crash.
The subframe is a component in a vehicle's chassis that houses the engine and steering components.
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  • Written By: Lori Kilchermann
  • Edited By: Jacob Harkins
  • Last Modified Date: 16 January 2015
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    Conjecture Corporation
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The subframe is a component in a vehicle's chassis that houses the engine and steering components. It is found in unit-body construction methods, which have been used worldwide on vehicles since the late 1970s. A subframe is typically constructed from welded steel tubing and is attached to the vehicle unit-body by bolts. The subframe makes it possible to build the steering, engine and transmission assemblies in one location and install the finished product in the completed vehicle in another location.

Vehicle manufacturers have been using the subframe for decades with great success. This technology was first used in aircraft production. Aircraft manufacturers found that by building the craft in small sections, they could be assembled later and a completed airplane could be assembled much like a giant jigsaw puzzle. Ship builders adopted the assembly method and soon ships were being constructed by assembling smaller, easier-to-handle subframe type components.

When the automobile manufacturers began using subframe assembly methods in new cars, buyers were skeptical and sales dropped. It was thought, by the consumers, that the vehicles would not be as sound and strong as those possessing a full frame. Testing soon revealed however, that these vehicles with unit-body construction and a subframe were actually safer than the full-framed counterparts. Sales picked up and buyers felt comfortable driving and riding in the vehicles.

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The added safety results from the unit-body construction's ability to absorb and dissipate energy in the event of a crash. By working as a series of components rather than a single, solid piece of steel, the chassis is able to safely absorb energy one piece at a time. This effectively spreads the force of the impact out over a wide array of components and lessens the force on the vehicle's occupants. Many racing-type vehicles have since adopted this type of construction in an effort to reduce driver injuries.

With the vehicle being assembled from different component groups, maintenance is actually decreased in cost as well. By having the ability to remove broken parts as an entire sub-group, mechanics are able to reduce repair time. This translates as cost savings to the vehicle owner. This has come in further in favor of the consumer as manufacturers build modern automobiles with a front and rear subframe, making it even easier to repair.

It is also now possible to remove a damaged subframe and simply slip a new one in its place. This eliminates costly time on a frame straightening machine and large repair bills. The automobile has come a long way from the small rigid chassis of the first cars to the painstakingly designed vehicle chassis and components of today.

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Soulfox
Post 2

@Logicfest -- People might say those older cars can take more of a beating, but I do believe that notion has been debunked many times over.

The thing about newer cars is that there is an incredible emphasis on safety. Seat belts, air bags, bumpers that absorb the brunt of a head on impact and, yes, subframes are all things that make cars safer than they used to be. I remember a 1955 Chevrolet Bel-Air that my parents had. It didn't have seat belts but did have a metal dash that could crack your skull open if you hit it in a crash.

Don't get me wrong. Those classic cars are great, but they don't hold a candle to the vehicles we drive these days when it comes to safety.

Logicfest
Post 1

I know for a fact that an automobile with a subframe is tough. I got in a wreck once with an older car that did not have a subframe and I came out better in the crash. I didn't have a huge car, either. It was just designed very well and that subframe absorbed a beating so I didn't have to do that.

That was an eye opening experience because I had always heard that older vehicles were better able to protect passengers than newer vehicles built on a subframe.

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