I have heard two different opinions about the feasability of successfully straightening a bent car frame. Some say that it cannot be done, other’s say that the newer machines can return the frame to true. Anyone know the story about this. The frame has fairly minor damage.
Depends on your definition of “successfully.” Frame racks have always been able to return most cars to the point of getting the parts back on and the doors to open and close, but returning a car to the perfect alignment of pre-crash days can be impossible no matter how fancy the machine is – all it takes is enough metal damage for the frame to rupture under tension.
Well first off, most cars don’t have frames as such anymore. Most cars are built with unibody construction. Meaning that the panels themselves make up the frame, there is not a seperate frame that the body bolts to. (Pickups, and SUVs built off pickups still have body on frame construction )
Getting back to the OP, the new frame machines can pull a bent unibody back to straight with an amazing degree of sucess. The degree of sucess depends on A)How good a machine is being used B) How badly bent the car is C)How skilled the operator of said machine is.
Let’s put it this way, I have seen cars straightened to the point that I could not detect any problems with a state of the art four wheel aglignment machine. Not only were all of the angles within spec, there were all near the middle of the normal range.
Then again, I have seen cars drive though puddles and leave 4 seperate tracks on the dry pavement afterward.
There are some great body guys out there, there are lots of hacks.
I’ve heard about the puddle test for a bent frame. How exactly is it performed?
You are driving down a road, the car in front of you drives through a puddle. Look at how closely the rear wheel tracks match the front wheel tracks. In the car is going straight, there should only be two tracks. If the car is crabing down the road, the tracks will be wider, or there will be four sepeerate tracks.
This is a very crude test. A four wheel alignment machine or a frame machine is much more accurate.
Rick pretty much nailed it. Folks who toss out the phrase, “It’ll never be the same” usually are the same ones who saw similar damage 20 years ago. Technicians & their machines have come a long way.
Frame “rails” are still used in mounting the front end of a car to the body and to support the rear somewhat. The front third of the car (firewall forward) is designed to more or less completely collapse in a front end collision. The idea is to conatian as much energy in this area as possible before transferring it to the cockpit. It is often a viable repair technique to chop off the front end and weld another on (called a “Front Clip”). But this really freaks out the owner who doesn’t always have a purely objective perspective on the car, and also doesn’t realize that this is basically how the thing was made to begin with.
Gosh, after an almost four year hiatus, I’m back in body-in-white. I’ll tell you that if I have a front end collision, even *I[i/] want the insurance company to total the car, and not do the repair that you describe! 'Course I mean car, not truck, which are completely different beasts, construction-wise.
I’ve (thankfully) never had a collision that involved the use of a frame straightener. But with unit-body construction, I think I’d still have my doubts until seeing the machine in action. Unibody is so completely different than body-on-frame, and everything welded to everything else, there’s a lot to be missed. Unlike the repair above, I could probably be convinced. And probably on Rick’s word; he always knows what he’s talking about.
I have to say, I’m torn on this.
I witnessed many a crappy repair job on unit-body cars, to the point where I always advised people to try to get the insurance company to total the car, even if you had to (actually, with lawyer’s letter) threaten to sue.
However, in the past few years I have witnessed some excellent repair jobs of horrific damage, where I got under the car, inspected seams, measured clearances, tapped and prodded, and did every test I could think of and could not tell that the car was anything but factory fresh. In two cases I know of the cars still acted perfectly several years later.
I’m now convinced that some shops can do an excellent job, but the key question is how does one find such a place.
I **do ** total 'em. I should have been more clear–just because it is structurally viable doesn’t mean it’s a good idea. At best you’re getting an unknown front end (from a car that has been totaled for some other reason, I might add) and at worst the guy doing the replacement may not know what he’s doing. It’s rarely economically feasable, and few technicians will do it–best just to take it out back and shoot it.