Structure vs. Frame


I am sure you have seen the commercials where the latest model vehicle will parallel park, brake, keep you in the correct lane or even put your boat in the water all by itself. While all the new technology is great, the collision industry is missing an important correlation between Advanced Driver Assistance Systems (ADAS) and structural alignment. In fact, we can confidently say the majority of collision repairers are missing about 40% of structural misalignment. To put it another way, approximately 4 out of 10 vehicles you write estimates on have structural misalignment and there are no visual indicators such as, misaligned panel gaps.

Why panel gap movement has changed?

Two words, pedestrian safety! Have you noticed that on most vehicles the fenders do not bolt directly to the upper fender apron rail? The fenders are bolted to perches that are weak and bend easily. This is not a design flaw, but an effort to reduce severity of injuries to a pedestrian if struck, allowing the collison energy to be absorbed by the vehicle and not the pedestrian .

These pedestrian safety advancements coupled with new structural substrates such as, advanced steels and aluminum, allow for structural movement without any changes in the panel gaps. So, what does this mean for our ability to use traditional visual indicators to determine the need for a structural/frame repair? The reality is, panel gaps are no longer reliable to use as the determining factor regarding whether a vehicle needs to be measured for structural misalignment.

As we provide training to collision repairers across the USA and Canada, we find there is a considerable gap in understanding how to write structural repair. Estimators have been convinced that a structural repair is different than a frame repair. We have also seen structural repairs written at the body repair labor rate. When asked why they write that way, we always get this answer, “the insurance company said that’s how to write it.” Let’s break this down so everyone can understand it.

What is a frame?

It depends on the vehicles construction. Most passenger vehicles today (except for some large SUV’s and pickups) are unibody construction. In a unibody vehicle, the frame components, floor pan, and chassis components are built together as a single structure. In this type of vehicle construction, the unibody structure is the frame. Some large SUV’s and light passenger trucks are constructed with a unibody structure that is attached to a separate frame. This type of construction is called “body over frame”.

In unibody vehicle construction, the suspension and drivetrain components are attached to the unibody, in “body over frame” construction, the suspension and drivetrain components are attached to the frame, not the unibody.





Writing to repair the structure.

The key to bidding repairs to the unibody or frame is not in defining if the structure is a frame; it is, instead, defining the type of repair needed. There are two types of repairs to a unibody structure or frame.

  1. Non-Structural Movement – When the unibody or frame has minor collision damage, and there is no movement of the structural component it is not a “frame repair,” because the reason for the repair is to restore the corrosion protection and the cosmetic appearance. This type of repair is no different than any other body repair. However, don’t just lump these repair into one line. Bid each component individually as you would the fender and door.
  2. Structural Movement – When a structural or frame component has moved from its original location, then a frame realignment and repair is required. To properly repair this type of damage, the technician must first measure the vehicle. Once the extent of movement has been determined, the vehicle needs to be set it up with clamps or fixtures to hold the rest of the vehicle in place while the structural frame component is repaired and returned to its original position.

This type of specialized work should be considered at the higher frame rate; as it requires expensive equipment, expertise, training, and years of practice to perform. The structure is the most crucial part of the automobile protecting the occupants.

Not only for protection

The vehicle’s structure does much more than just protecting the occupants in today’s vehicles. Advanced Driver Assistance Systems (ADAS) use the vehicle’s structure to determine the many calculations required to ensure the collision avoidance ADAS technologies are correct.

Have you ever wondered how the forward braking assist, intelligent cruise control or blind-spot detection ADAS know where the vehicle is in real-time and space when traveling at various speeds? The wheel alignment informs the steering angle sensor calibration, and the steering angle sensor is one of the variables used to determine where the vehicle is relative to other objects around it. The four-wheel alignment, especially the thrust angle, is the mechanical measurement that informs the electrical components.

What do you do?

Measuring structural movement is not just about repairing it anymore. It includes confirming the location of ADAS sensors in 3-Dimensional space. Have you sent a vehicle for ADAS sensor calibration only to have it sent back because it cannot be calibrated? Having to bring the vehicle back to your shop to perform the additional repairs required to properly position the sensors costs time, which in turn costs you money. If you do not take the time necessary to confirm that the structure is repaired correctly and the ADAS sensors are in the correct position, it can cost someone their quality of life or even their life. The day has come that we must pre and post measure the vehicle’s structure to identify damage for repair and confirm the repair were completed correctly.

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Tags: Structural , Frame , Unibody ,

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