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Installing subframe topside brace on welds

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    Installing subframe topside brace on welds

    Has anyone done reinforcement plates plus an x-brace, with the upper spot welds boxed-in?

    My plates and upper "triangle" welds are done, as shown in the attached pic from Turner's instructions.

    X-brace is going on next weekend.

    How flat do the triangle welds need to be before the subframe brace is bolted down? Meh-flat? Flat-ish? Perfectly flat? If it needs to be perfectly flat, How did you grind it, and how did you check it for square?

    Thanks

    #2
    My guess is perfectly flat. That welding step in the Turner instructions is pretty unnecessary if you are bolting in a topside brace to the rear subframe mounts.

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      #3
      Originally posted by Slideways View Post
      My guess is perfectly flat. That welding step in the Turner instructions is pretty unnecessary if you are bolting in a topside brace to the rear subframe mounts.
      I decided to do the brace after doing the upper weld. But the instructions for the brace(s) make no mention of flattening the factory welds or the T.

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        #4
        Originally posted by 1000hp View Post

        I decided to do the brace after doing the upper weld. But the instructions for the brace(s) make no mention of flattening the factory welds or the T.
        Does the brace mount the the rear shock towers? You probably want the brace to sit perfectly flat on all the mounting points so the brace is not at a slight angle.
        Last edited by Slideways; 10-19-2025, 09:39 PM.

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          #5
          Originally posted by Slideways View Post

          Does the brace mount the the rear shock towers? You probably want the brace to sit perfectly flat on all the mounting points so the brace is not at a slight angle.
          It does.

          I'll aim for perfectly flat. Should be fun grinding welds with a dremel through a two-inch hole 🥲

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            #6
            Originally posted by 1000hp View Post

            It does.

            I'll aim for perfectly flat. Should be fun grinding welds with a dremel through a two-inch hole 🥲
            Good luck - I used a carbide burr on a die grinder and that was a hard enough job. Going to take a while with a dremmel!


            Sent from my iPhone using Tapatalk
            2005 ///M3 SMG Coupe Silbergrau Metallic/CSL bucket seats/CSL airbox/CSL console/6 point RACP brace/Apex ARC-8s
            Build Thread:
            https://nam3forum.com/forums/forum/m...e46-m3-journal

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              #7
              I personally decided to leave them be. Why cut them ? They are a structural shape of the chassis and there is, from my point of view, no upside to cutting them and flattening them.
              The rear brace will be perfect sitting on top of those T shaped forms and you won't compromise that part.
              But that is just my vision of this.
              2004 E46 M3 • TiAG / LSB nappa

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                #8
                Click image for larger version

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                Expose and grind
                Attached Files

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                  #9
                  Originally posted by Flow View Post
                  I personally decided to leave them be. Why cut them ? They are a structural shape of the chassis and there is, from my point of view, no upside to cutting them and flattening them.
                  The rear brace will be perfect sitting on top of those T shaped forms and you won't compromise that part.
                  But that is just my vision of this.
                  It's not the T I'm worried about, it's my welds connecting the stock spot welds, similar to what is shown in the pic. If my welds are lower than the T, I'll leave it alone. If they're taller I might be suffering for a while to bring them down.

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                    #10
                    Originally posted by DJM View Post
                    Click image for larger version

Name:	weld.jpg
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                    Expose and grind
                    The cover plates are already installed, welded, seam-sealed, and painted. Definitely not removing all of that.

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                      #11
                      Originally posted by karter16 View Post

                      Good luck - I used a carbide burr on a die grinder and that was a hard enough job. Going to take a while with a dremmel!


                      Sent from my iPhone using Tapatalk
                      Yeah, not looking forward to it. Were your spot welds connected? Or did you grind down the stock stuff?

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