Originally posted by: Evadman
A good body shop can true the frame on a machine. but I would not want a unibody car that has been on one. Steel (just like most everything else) has memory, and can return to the previous position over time. The steel can also be weakend when this is done depending on how bad it is. I got into a discussion with someone here on this exact topic, but I hold firm in my beliefs
Yes, it has a memory, in the shape that it is originally formed, that's what allows you to bend it back. It is possible, and it is done thousands of times every day. It is perfectly acceptable if done within manufacturer guidelines. It is a MYTH that once a frame is bent, the car is totalled. It is not economically feasible sometimes, meaning it will cost more than the car is worth to repair or replace damaged structural items.
A unibody car has no frame, rather, many parts of the body are welded together to form the load bearing structure. Quarter panels, rockers, a,b& c pillars, aprons, roof, etc. are all considered structural parts of the car. IIRC, the Probes used high strength low alloy (HSLA) steel in the structure. That steel can be straightened if it is not mashed or the metal has no kinks in it. If it is smoothly bent, without a crease, it can be straightened with little or no heat. Each different car manufacturer has different tolerances. The German and Japanese cars have the smallest tolerances, (plus or minus 3 mm), whereas some domestic cars are as much as plus or minus 5 mm. This is pretty significant, if you consider a given point on one side can off to the left on one side 3mm and off to the right 3mm on the opposite side. This gives us a total of 6mm difference, and still within tolerances from the factory! A good frame man, with the right equipment can get the different measurement points much more exact than they are coming right out of the factory. Yes, many hack shops, will heat the metal to the point that ruins the steel, and it will be within tolerances, but the steel will not be as strong structurally as it was before the accident. That's why manufacturers have guidelines, they will tell you what parts can be heated and to what temperature without ruining the structural integrity. If the part cannot be straightened within the manufacturers guidelines, the part or parts must be replaced. The manufacturer also has guidelines that specify what welding equipment (MIG or TIG welders) and techniques must be used so as to not to unsafely heat the undamaged part you are welding to, which ruins the molecular makeup of the steel. If the manufacturers didn't think a part could be safely replaced, why would they open themselves up to the liability of selling a part that could not be safely replaced? Remember, these same manufacturers have bodyshops of their own, and they provide training to their technicians. If what Evadman says is true, a manufacturer would or could have their reputation ruined in a large class action lawsuit from unsafe repairs or techniques.
Evadman and I have had this discussion before. I have been to several frame straightening schools and tell you from experience and knowledge that it can be done safely without ill effects. The key is having the proper knowledge and equipment to doing it properly, to include the measurements of the car in question (They're available from several companies, try Chief or Mitchell for starters)
Evadman is uneducated in body and frame work. Like I told him during the last discussion, he needs to educate himself before giving out false information.