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Thoughts on seam welding

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  • Thoughts on seam welding

    I'm on the fence about seam welding my chassis, so your opinions regarding the worthwhileness of actually doing it will be appreciated.

    Basically, I'm trying to weigh the pros (some rigidity, but how much?) vs the cons (a lot of work/time). That probably sounds lazy, but I'm really trying to finish the car up soon. I think it's really hard to judge how much it will help since no one (probably) just seam welds the car seperate from any other upgrades.

    I'm planning on doing a half cage in the future.
    500# f/various rear rates
    whiteline front bar and stock rear.

    I'm thinking I should just nut up and do it. Thoughts?

  • #2
    What are you using the car for? If you're going to be drifting it, I feel it's a waste of time. Plus, it will probably cause more damage to the chassis when you wall ride the rear of the car.
    My Blog | Unfriendly Garage | Endurance Motorsports


    • #3
      DEs. Maybe some autox, and up until this post, I hadn't really thought about classing. I'm pretty sure seam welding isn't SM legal. So maybe that settles it, for me anyway.


      • #4
        S13 or S14?

        IIRC, S14's have 50% more torsional rigidity...

        So for an S13 it might be more beneficial than an S14.

        - Brian
        '96 240SX | KA-T - 320rwhp @ 12psi | ~2700lbs
        Koni 8611 & GC's - 600/450 | RPF1's - 17x9.5


        • #5
          That would probably bump you all the way to prepared. Definitely not SM or anything with "street" in it. And it's not like you can un-do it.


          • #6
            Originally posted by PerilousActs View Post
            What are you using the car for? If you're going to be drifting it, I feel it's a waste of time. Plus, it will probably cause more damage to the chassis when you wall ride the rear of the car.
            Stiffing up the chassis is beneficial for drifting. It makes initiation much more predictable and snappy. It also speeds up and ads predictability to how quickly the car takes a set after lateral weight transfer.

            Even a cheepo eBay rear strut bar makes a noticeable difference on the back of an S13.

            Roll bars/cages and seam welding are night and day improvement in chassis rigidity for drifting and make the car feel much more solid and predictable.

            All the pro drift cars are seam welded. They mitigate the crash damage issue by fabricating tubular crash bumpers for front and rear and making the main chassis and suspension pickup points as ridged and reenforced as the rules allow.

            For a street driven fun drift car it is overboard. Most people are not capable of doing the work and the time investment is more than what most are willing to do. A roll bar or cage will provide much of the same benefits plus allow tandem.

            For a good example of a well prepped, seam welded drift chassis see:
            The Nerd shall inherit the podium for knowledge is power.


            • #7
              Oh, I understand the benefits of doing it (in the process of seam welding my chassis). I was just saying it's not worth it for an am level car that's going to bash a wall without parts designed to take it instead of transfer a lot of it through the rest of the car, as it'd be a huge waste of time.
              My Blog | Unfriendly Garage | Endurance Motorsports


              • #8
                A monocoque chassis seems to lose stiffness some as it ages. At least that's my subjective impression. Perhaps just the rattles increase on my old cars.

                I've seen nicely caged 240s, front-halfed, back halfed, etc. Even one or two full tube frame retrofits. Very nice stuff. For stiffness and overall safety, I think i like a 6 point or better cage, fully welded, with proper pedestals or plate flanges. Ultimately, I'd like to see that tied into the existing monocoque at all of the roof pillars and wherever else possible. Integrating the two into one creates even greater overall stiffness than with the two joined only at the base.

                I'd also try to increase the beam stiffness of the "frame rails", especially at the front by forming some sheet and or tube bracing. Tie the upper and lower rails to the firewall at a point further in towards the center.

                You can also increase stiffness in the rear by using solid subframe spacers. It will increase harshness, noise and vibration and sacrifice compliance, but once again, tying the two together will certainly increase stiffness.

                As far as seam or stitch welding, I think the gains are minimal in comparison to adding tube or sheet bracing. Welded and integrated, non-pivoting construction, unlike your typical easy to install and adjust strut bar, should be used.

                Hope my long posts don't bug anyone. I don't mean to thread jack, I just like my morning coffee.


                • #9
                  Seam welding has been greatly exaggerated these days. And most don't do it with any kind of saftey or repair in mind. My s13 is caged and welded and I can tell you it does make a noticeable difference but I didn't seam weld anything. What I did on my car is reinforce the naturally weak areas. The s13 is notoriously weak at the a-pillar firewall area. The best thing you can do is add the under fender braces, under braces for the subframe, and a triangulated strut tower/firewall brace. All are legal in almost any class and a bolt on. That is going to fix more than half the problem. A good cage is about the only thing you can do to fix the torsional stiffness. Seam welding does very little by itself. On top of that, welding any HSLA steal weakens the metal counter acting the problem. Plug welding in between that factory plug welds does far more good than seam welding. Parts of the floor pan are just a waist of time to weld. Here is a little food for thought, spray on best liner. I sprayed the inside and underside or the floor pan in my car with bedliner pretty much laminating the floor. It was the best move I made. Durrable, easy, cheap, looks great, legal in anything, quiet, and added structure. Huge misconception about his much it weighs. Less than 5 lbs total! So less than the factory sound deadening. And that added more structure than any welding cab do.


                  • #10
                    OK, rereading that makes IR look like I didn't weld anything on my car. Not true. Plug welds on between every factory plug weld around the strut towers, aprons, and pinch seams joining the floor and rockers. I welded in under fender braces and the cage. I did NOT do any welding on the core support or the rear body simply because I know I'm going to stuff it at some point and the energy it takes to replace an extra welded core support is not worth the tiny benifits of a little bit of strength to the front end.


                    • #11
                      I'd suggest going with a roll bar or a basic 6 point instead of the time to seam weld.

                      Will seam welding it hurt anythign? No...but the cost/time to benefit ratio to me is not worth it, this side of a full on semi compeitive race car...and even then it may be a stretch.

                      ...if you have nothing better to do/bored then why's only your time, and the cost to weld...but if you're paying someone I'd skip it.
                      'Slicks on a car show me you care - broken axles show me you're trying'
                      [I]Nitrous Rental Cars - Turbo Festivas - Vehicular Lunacy[/I]