Frame Straightening: Pulling Your Car Back into Shape
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Frame Straightening: Pulling Your Car Back into Shape

Frame straightening sounds scary, but it’s more common than you’d think. Frames are bent in about half of auto accidents, making this a regular part of autobody repair. Here’s how a little bending, cutting and welding can bring your car back to its original shape and performance.

Why is Frame Damage so Common, and What does it Do?

Collisions exert tremendous forces on your vehicle, and one way or another, those forces will reach the frame. Aside from weakening the vehicle’s structure, it also pushes parts out of place. Trying to replace body panels on a bent frame will lead to fitment problems, and there will be underlying mechanical issues. For example, if the axles aren’t lined up correctly, the vehicle will “crab,” going down the road at an angle to keep all four wheels turning in the same direction.

Modern cars have frame rail sections built to bend in accidents. This “crumple zone” absorbs some of the impact force before it can reach the cabin. As a result, damage to the front and rear of the frame is far more common than damage to the straighter, stronger sections under the cabin.

What is a Frame?

There are three major types of frame designs:

– Body-on-frame or ladder frame: The body of the car bolts onto a separate frame. This is common on trucks, large SUVs, vans and antique cars.

– Unibody: The frame, floor pan and sometimes the aprons and rear supports are built as a single unit. This makes the vehicle lighter and lower to the ground. Most modern cars, mini-vans and crossovers use unibody construction.

– Spaceframe: The frame stretches across the entire vehicle from the floor pan to the roof. This design is lightweight, and it’s great for occupant safety, but it’s also expensive to produce. This design is used in some high-end luxury cars as well as Jaguars and Saturns.

The frame is just one part of your vehicle’s structure. Several major components are bolted, riveted or welded to the frame and provide support for the rest of the vehicle.

Pillars: These support the windows in your vehicle. They’re lettered, starting with “A” for the pillars supporting the windshield.

Core support: This section sits behind the grille, supporting the front of the car. It’s often called a “radiator support” because the radiator is often mounted here.

Firewall: This metal plate separates the engine compartment from the cabin.

Aprons: These inner fender supports run between the core support and the firewall. They support the front suspension.

Floor Pan: This metal sheet makes up the floor of the cabin. It also has channels to run wiring from the front of the car to the rear.

Rear support: This is like the core support, but it’s on the back of the vehicle. It supports the bumper and trunk floor pan.

How does a Frame Machine Work?

The car is attached to a platform surrounded by posts. These posts move around the car, using laser sensors to measure how far off the vehicle is from factory specifications at several points on the body. To repair the frame, the vehicle is tied down to the platform, then chains are attached between the frame and the posts. A hydraulic system moves the posts, slowly pulling the frame back into shape. The vehicle is remeasured and stretched a few more times until everything is within the manufacturer’s specifications.

Is Bending Enough to Repair the Frame?

Imagine crushing a soda can and then trying to bring it back to its original shape. Even if it’s pushed back into its original can shape, it will still be a little deformed where the metal folded, making it weaker. While your car may be brought back into spec using a frame straightener, it may need further repairs to restore its strength. New sections of metal may need to be welded in to replace bent sections. If the damage is too severe, the vehicle may need to be scrapped. Other structural components are usually easier, and cheaper to replace.

Even after minor adjustments, the frame and structure will need some TLC. Just as paint will peel off if a body panel is bent too much, underbody coating will flake off of the frame.

Get Your Car Back on the Road with Merton Auto Body

Do you worry that your car won’t be the same after major collision repair? Are you concerned that insurance issues will keep your car off of the road longer? Bring your car to Merton Auto Body. Over the past 70 years, we’ve offered Lake Country residents the best repair service possible. Our staff has the latest repair training and qualifications, and we have an on-staff appraiser who will work with your insurance company. Our shop is just south of Silver Spring Drive in Merton, right in the heart of Lake Country. That means we’re close by, whether you’re in Pewaukee, Hartland or North Lake.


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