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This is a sample of the handout that is used in our live educational seminars.  It provides information on how different construction characteristics change how the car should be evaluated, and how to properly asses collision damage using what is known about  the industry and other resources.

"How to prove collision damage:

A view from both sides of the fence."

Presented by Future Forensics™ and VeriFacts Automotive LLC.

Please contact the Future Forensics office for dates and times of the "How to prove collision damage: A view from both sides of the fence" Seminar series.

Office: (206) 362-2835 Toll free: (888) 362-2511 E-Mail:

The information contained in this document is generic and in no way is meant to be used on a specific vehicle. Always refer to the vehicle makers body repair manual for the specific characteristics of the vehicle in question.

Why Future Forensics™?

1. The need for a better understanding of how cars are damaged in a collision and how to document that damage.

2. Discuss how every vehicle is different and that you can not use the cookie cutter method of  analysis when trying to analyze vehicle damage.

I. Frame/Structure Designs:
1. Unibody Design:

  • can be made of mild steel, high strength steel, aluminum, plastic.
  • steel structure all welded together to make one body or "unibody".
  • outer body panels made of steel, aluminum, plastic.
  • each car style has it's own energy absorbing characteristics.
  • passenger cars have energy absorbing bumper assemblies and crush collapse zones.
  • damage analysis is logical but due to the tight/compact design; damage is often not visible on first glance unless major.
  • plastic can be especially hard to detect damage due to the "memory effect" where plastic will spring back to "shape" and steel usually does not.
  • sometimes will require a vehicle be "torn down" to find all damage.
  • manufacturer tolerance usually +/- 3 mm. some as little as +/- 1mm.
2. Space Frame Design:
  • a type of unibody.
  • outer panels are bolted, glued. riveted, or a combination of these.
  • most outer body panels and bumper covers are plastic.
  • will "hide" damage.
3. Full Frame:
  • lower full frame and the body is usually bolted together with rubber grommets in between them.
  • not as logical to find damage as the unibody due to bolted on body to
    frame design.

    • ladder style (trucks): one solid rail on each side with crossmembers connecting them together. Body bolted on top of frame giving vehicle a higher center of gravity. Most are solid but some have front crush collapse zones.
    • perimeter style (cars): have side rails as the ladder frame but usually have rear kick ups and front offsets that can absorb collision energy.
    • lower center of gravity as the car body generally sits inside the frame     and is bolted on rubber grommets.
  • some may have a manufactured tolerance of +/- 5mm or more.
4. Combination Designs (hybrids):
  • have a full frame lower and a unibody upper and require the use of full frame diagnosis and unibody diagnosis.

II. Bumper System Component and Design

A. Components:

  • 1. Bumper Covers:
    • usually cosmetic and made of thermoplastic or thermoset plastic.

  • 2.Crushable energy absorbers:

    • designed to be crushed on impact and absorb collision energy.
    • some vehicles use to hold cover in proper form and shape.
    • usually replaced unless the manufacturer has a specific repair procedure.
    • usually located between the outer cover and the reinforcement bar.(sandwiched in between)
    • usually cannot be seen with the bumper cover on the car.
    • can be made of foam, plastic, or similar materials.

  • 3. Piston/Mechanical Energy Absorbers:
    • designed to absorb collision energy.
    • crush, collapse, or move on impact, some go back to original state in minor impacts.
    • some must be removed and tests performed on them to determine if OK or have to be replaced.
    • can be reused even if it looks damaged- if it returns to original state and  shape and passes diagnostic tests as prescribed by the manufacturer.

  • 4.Bumper Brackets Design:

    • May bend or break in a collision depending on design.
    • generally located in between the car frame and the bumper bar or   reinforcement.
    • if damaged or broken usually replaced.

  • 5. Bumper Reinforcements/Bumper Bars:

    • made of a wide variety of materials:
      • steel, (mild, high strength, ultra highstrength)
      • aluminum.
      • plastic/composite.
B. Designs:

1.The purpose of the front or rear bumper (as it pertains to collisions) is to    direct the flow of collision energy into the frame rails where it can be properly managed by design. Some are designed to absorb some of    the collision energy and especially in minor impacts may keep the damage    limited to the bumper system only.

2. Bumper designs include but are not limited to:    
  • cover/crushable energy absorber/reinforcement.
  • bumper reinforcement-bar/brackets.
  • reinforcement bar/mechanical energy absorber.
  • composite bumpers with the reinforcement molded together.
  • cover/reinforcement-bar/mechanical energy absorber.
  • cover/reinforcement-bar/brackets.

3.As new cars are being designed, manufacturers are designing new and
   unique bumper systems.

4. Most bumpers have a rating attached to them (2.5 mph, 5mph, etc.).

5. Bumper systems must be analyzed on a case by case basis as they vary      widely.   


1.Unibody and space frame vehicles:    
  • contain crush/collapse zones in the front and rear frame rails designed to absorb collision energy
  • designed to force the collision energy around the passenger compartment (into the roof and rockers).
  • have specific repair/replace recommendations.
  • vary widely from vehicle to vehicle.
  • have specific repair procedures.
2.Full frame/perimeter frames:
  • may have crush collapse zones in them.
  • may or may not direct collision energy around the passenger compartment if they are designed too rigid.
  • vary widely by design.
  • Use a systematic approach in a logical order:
    • look for uneven panel gaps.
    • proper/improper operation.
    • cars damage in a cause effect relationship.
  • Teardown the car and take the "damage hiding" parts off the car to find the bent/twisted metal and crushed energy absorbers.
  • Sometimes structure damage can only be positively identified by precise three dimensional measuring.
  • 30 to 40% of the frame rail damage can only be seen from the underside of the vehicle, so also inspect the vehicle from the underside, preferably on a lift for overhead inspection or crawl underneath.
  • Minor collisions may have hidden damage.
  • Bumper absorbers, frame rails and other collision energy absorbing parts of the vehicle, in many cases cannot be seen without tearing the vehicle down.


1. Most estimates are written with the philosophy of: "write only the visible damage".

2. It is very common that after the car has been "torn down" there is more damage found.    
  • the process is called a supplement or additional and each insurance company usually has a phone number to call if more damage is found.
  • the damage that is found after teardown sometimes is the bumper absorber, reinforcement or damage to the structure/unibody.
3. Some estimates are written for best case scenario with the understanding that the body shop can call if it does not repair as first thought.
  • this could mean the difference of trying to repair a quarter panel - but it does not work -so it requires replacement. ( a major welded on part of the car).

1. Improperly repaired vehicles can also cause problems:
  • if a frame rail has been repaired/replaced improperly it can cause the car to react differently than it would had it not been previously repaired.
  • some prior repairs are responsible for major injury to vehicle occupants


  1. Photographs as soon after the accident as possible.
  2. Frame measurement data sheet showing any vehicle misalignment.
  3. Photographs after the vehicle has been torn down, and during the repair if possible.
  4. Photographs of the major collision protection parts of the vehicle that were damaged and comparative side to sides.
  5. A narrative description of the vehicle and the damage to it by a qualified person.
    • -this report should include the bumper type.
    • -car type (unibody, full frame, etc.) and detail the damage to it.
  6. A copy of the completed repair invoice for the vehicle if it was repaired.(call the body shop).

Please contact Future Forensics directly for the dates and times of the "How to prove collision damage: A view from both sides of the fence" seminar series.

The information contained in this report is not intended to be a complete and accurate representation of all variables. It is intended as generic information about vehicles and the collision repair industry. In no way should it be used for other than reference. Always refer to the body repair manual for specific information and manufacturer recommendations.

Future Forensics™
Office: (206) 362-2835 Toll free: (888) 362-2511

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