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What is a pinch weld?

edited October 2012 in Repair and Maintenance
Can someone please explain what a pinch weld on the unibody frame of a car's undercarriage area is, please?

Thank you.

Marnet
......still reading, still learning.....
«1

Comments

  • I believe they would be referring to spot welds that are created by two electrodes pinching two pieces of sheet metal together, then applying high voltage to them to weld the two together. More specifically though I think it is referring to the ridge or flange under the unibody that are the normal jacking points. Don't know what it is called but the reinforced flanges where you put the jacks.
  • edited October 2012
    The pinch weld is where two pieces of metal are welded together to form the lower chassis of the car. It runs from behind the front wheel well to before the rear tire well underneath the doors. Why do you ask?
  • If you want an analogy, think of clamping 2 pieces of paper which represent metal, between the tips of a thumb and forefinger. That's how spot welding works and it's pretty common with automobile sheet metal assembly because it's fast, easy, and cheap.

    Don't tell me that recent bump in the road busted some welds on your Impala?
  • BustedKnuckles is on the right track. Look at the rocker panel and you will see a flange about 3/4" hanging down. This is the pinch weld, for lack of better terms this is where the floor is welded to the sidebodys.
  • Yep, that 70mph hit on the broken/raised section of road on the interstate has done a real number, as in $$$$ on the car. Dealer service assessment is that the left front strut, strut mount and bearing need to be replaced and the front end aligned. About what I expected. They found no sign of problems with the wheel bearings. Referred me to a body shop to look at the undercarriage further due to contact evidence where the car bottomed out on the upraised sharp edge of the paving section.

    Body shop found that the car appears to have bottomed out directly under the front seats, especially on the left side immediately under the driver's seat. The impact appears to be worst directly on the pinch weld with damage to the weld, noticable deformation upwards and scraped bare metal that will now be subject to rust.

    My options, according to the body shop (and depending on what settlement I come to with the insurance company) are to:
    a) ignore the damage but definitely end up with major rust and very likely some compromise of the unibody structural integrity;
    b) just paint over the area to avoid rust but still have questions about the frame integrity;
    c) let them remove the front seat (I have the split bench), roll up the carpet, and find just how badly the upward deformation damaged the inner layers of the metal.
    They spoke of potentially needing to weld studs on to pull on to pull the area back down into proper shape and conformation depending on just how bad the damage is.

    I will say that bottoming out at 70mph directly under the driver's seat was the hardest impact I've ever felt. Scared me greatly. I still can't believe I didn't blow a tire!

    I am taking the car to the independent mechanic shop tomorrow to have them diagnose what they find wrong with the car. I want a second opinion/estimate. I'm looking for consistency in what is found and recommended. It seems worth the extra diagnostic labor costs.

    I really like this car but my main priority is having a car that will be safe in the long term. If the structural integrity has significantly suffered, then I'll get it repaired with the insurance claim and then trade it in for a different car. I highly prefer to keep this one. It is, after all, paid for and one I like. But, too, it is only a machine that can be replaced.

    The car did its job, it kept me safe. The road hazard is ending up dinging my car, dinging my bank account, but not my life and health. For that I am profoundly greatful. All else is merely an expensive, time consuming annoyance.

    Oh yes, I'm approximately $200 out for about 3 hours total diagnostic time. The estimate from the dealer is $822 for the strut, strut mount and bearing repair. The body shop estimate to fully repair the unibody damage is $508. Once I get a second diagnosis and estimate, time to go back to the insurance agent and actually file a claim.

    But hey, the trip this happened on was coming home from my best friend's daughter's wedding! More happy times to the trip than this one road hazard incident.
  • Oh yes, and the body damage includes damage to the rocker panel too.
  • I forgot to say thank you to each of you for your explanations in answer to my question. I do thank you!
  • INTERESTING UPDATE:

    Independent mechanic shop agrees the sound might be from the strut but not necessarily.

    Indy shop suggests that rather than just replace the strut and not know if it will fix the problem that they hook up sensors which actually listen to various suspect parts, one part at a time, switching the audio feed from part to part, while driving the car and specifically locate the problem. Works for me! (Note: the dealership mechanic after over 2 hours time driving and looking is only 50% sure that replacing the strut, strut mount and bearing will solve the issue.)

    So, next Tuesday morning I leave the car with the indy mechanic for that diagnostic. I'm putting more money up front into diagnostic labor time in hopes of getting the damage acurately determined and fully fixed right the first time rather than throw parts at it in hopes that was what was needed. Maybe I'm being overly cautious but will at least have better peace of mind this way. Also, I expect that my extra due diligence efforts up front will get me farther with the insurance adjuster along with my sterling record of only two minor claims 18 and 24 years ago. (Rear ended and rock through windshield.)

    So, until Tuesday, it's go fight removing four 33-year old hugely overgrown yews and a forest of invasive Chinese honeysuckle. Using my great-grandfathers tools proved a killer to my arthritis. So, I've invested $40 in new arthritis friendly heavy duty pruning saw and pruning lopper. It's better than paying someone almost $1000 to cut down, uproot and haul all of the yews and honeysuckle away. I already pay for yard waste pickup in my trash bill. So, $40 of equipment, $10 to $20 worth of yard waste bags, some Roundup and stump rot chemicals already on hand, and sweat equity is far more affordable!
  • Well I really hope its worth it. I really can't see worrying much about the pinch weld. I would have hammered it back straight and painted it. On my old Riv, after some years, I went to jack it up and the jack went right through. I just carried a 2x4 after that for emergencies. Never seemed to affect anything.

    As far as the yews go, get a price first. I had a big triple river birch that was close to the house and the neighbors house. The tree service took it down for $250 including grinding the stump. They were done in a couple hours and all I had to do was watch. No grubbing tool, no grunting, chopping, hauling away, just watched.
  • I got to see the ding in the pinch weld today. If it hadn't been pointed out to me I wouldn't have been able to spot it. Frankly, I have trouble seeing how that can need removing the front seat, pulling up the carpet and such. I'm inclined to say make sure it won't start rusting and settle for that.

    As to the yews, I did get several estimates. Everyone wanted a minimum of $450 and up to remove four large yew shrubs and $600 plus to get rid of the forest of trash honeysuckle. So, I'm getting my exercise slowly cutting it all down, into small pieces and bagged to be picked up as yard waste by my trash hauler. County ordinance requires me to pay for trash, recycling and yard waste pick-ups whether I use them or not. So, since I'm already paying for yard waste to go away, I might as well make use of it. Just cut and bagged two more yews this evening. Got one big one to go. I will have to get a neighbor stronger than I to cut the last eight inches of big stumps for me. Someone who can handle a chain saw can do the task in 5 minutes.

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