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Thread: Boxed and Seam Welded Subframe

  1. #1
    Join Date
    Oct 2004
    Location
    Ohio
    Posts
    6,746
    My Cars
    E21 320i, e39 540i/6

    Boxed and Seam Welded Subframe

    I've spent a considerable amount of time taking measurements and researching the prospect of control arm relocation to improve control arm angle and the roll center of the e21. The problem I ran into was that to move the pivot point any amount to make it worth the hassle would require MAJOR surgery of the subframe. Plus, from my measurements the E21 already has a considerable amount of toe-out bump steer, and moving teh control arms upward will only make it worse. So, now I've decided to leave it alone and fix other weaknesses in the front suspension design first, like my low spring rates and lack of camber plates.

    But, while it was out of the car I noticed that the subframe is not boxed the entire length, and this is especially critical where the gussets meet the channel and where the control arms bolt on. Any force the gussets place on the side of the cross channel is not well supported since it isn't boxed, so I decided to box it in as far as I could without hindering control arm installation. I'm also going to seam weld the entire thing since it's all spot welded. Will it make any difference? Who knows, but its fun to do.

    I only laid 1" beads at a time and alternated from side to side to keep the heat down so I didn't warp it. Even after trying to degrease the whole thing oil would just boil out of the old seams. The oil did make it harder to weld and it's obvious when comparing the new plate welds compared to the old joints that were full of oil, but they're fuctional. I have a ways to go on it to get all the seams welded up, but at least its all boxed in now.

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    '81 320i turbo | t25, 931 CIS, 250hp, 13.92@100mph | 2.2L m10 Turbo Build | My E21 Videos |

  2. #2
    Join Date
    Jan 2003
    Location
    Mill Creekish WA
    Posts
    5,674
    My Cars
    97 M3/4/5 81 E21 72 Bav
    cool. I like.


  3. #3
    Join Date
    Aug 2003
    Location
    SoCal
    Posts
    11,867
    My Cars
    E21, E24, M3
    Good work! You're a genius, I can haz?

  4. #4
    Join Date
    Aug 2004
    Location
    Manila, Philippines
    Posts
    3,763
    My Cars
    Duke - '82 320i

  5. #5
    Join Date
    Oct 2004
    Location
    Ohio
    Posts
    6,746
    My Cars
    E21 320i, e39 540i/6
    Don't worry, once I"m done I'll clean all the welds up and paint her real purdy. I'll update tonight or tomorrow.

    '81 320i turbo | t25, 931 CIS, 250hp, 13.92@100mph | 2.2L m10 Turbo Build | My E21 Videos |

  6. #6
    Join Date
    Sep 2007
    Location
    Seattle, WA USA
    Posts
    264
    My Cars
    82 320i E21, 95 Porsche 911 Carrera, 95 MR2 NA
    Good work!

    Have you tested the tension on the control arm mouting points. The welds you put there may prevent you from properly setting torque to the control arm bolts.
    Marco = 82 320i Hennarot - 95 Porsche 911 Carrera - 95 Red MR2 NA Hardtop

  7. #7
    Join Date
    Jun 2008
    Location
    Dahlonega, GA
    Posts
    22
    My Cars
    '89 Civic, '82 320i
    Nioce!! In for the updated/finished pics.

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