Dear Tom and Ray:
I am in the Air Force, and last week when I was driving through the gate at the base, the security forces troop accidentally raised the security barrier on my vehicle (BMW Z4) while I was passing over it. The impact was loud and sudden. It raised my car up and then dropped it down, littering the street with plastic and rubber parts. I have been waiting a week for an estimate on the vehicle. There is damage to the front end and, of course, the undercarriage. The Check Engine light came on immediately. For some reason, I cannot get a straight answer about whether the frame was bent in the accident. How can I tell for sure? BMW says the only way to tell is by taking it apart. However, the insurance-approved garage put it on the lift and said, "It looks pretty good." Thank you for any help you can provide. — Bryony
Ray: Well, there's a lot we don't know, Bryony. We don't know how fast you were going, we don't know how far out of the ground the security gate comes up and we don't know where it hit the underside of your car.
Tom: But if I had to guess, I'd say your frame probably was not damaged. It takes a pretty serious collision to damage a frame.
Ray: The rubber and plastic parts probably are nonstructural pieces of the grille, the bumper assembly, the stone guard or the headlight and taillight assemblies that broke when the car came back to the ground. The Check Engine light could have been triggered because the wires of an oxygen sensor got knocked off. But we're just guessing.
Tom: The way you'll know for certain if the frame has been bent is by trying to align the wheels.
Ray: If the frame is bent, the four wheels will not be alignable. So my advice is take the car somewhere of your choosing for a four-wheel alignment before agreeing to accept it back from the insurance company as "repaired."
Tom: Right. When the insurance- approved garage says it's ready, make an arrangement with them to get the car to a shop that you're paying to do an alignment. You want them working for you.
Ray: If the wheels all align, you can accept the car back and not worry about it. But if your shop tells you that they were unable to align the wheels, then you have the evidence to make the insurance company either fix the frame or replace the car.
Tom: So we can't tell you whether the frame has been bent, Bryony. But an alignment shop will be able to. And just to make sure this doesn't happen again, consider scraping off those "Go Navy!" bumper stickers before trying to drive onto the base again.
(Car Talk is a nationally syndicated column by automotive experts (and brothers) Tom and Ray Magliozzi. Write to them at the Car Talk website.)