GO FISHING, use SLABSAUCE Fishing Attractant
Page 1 of 3 123 LastLast
Results 1 to 10 of 21

Thread: New E34 Touring mod - Rear Strut Tower Brace

  1. #1
    Join Date
    Dec 2003
    Location
    Lincoln, NE
    Posts
    559

    Default New E34 Touring mod - Rear Strut Tower Brace

    Ok, one thing has always really bothered me about my Touring. Compared to a sedan, the Touring body is REALLY flexible. Between the 4 foot opening in the roof, and the huge opening in the back, there's just not enough structural rigidity to do the E34 chassis justice. With a lowered stiffened suspension, this problem is just amplified, especially in the rear.

    Long-term, I want to do some seam-welding underneath the car and maybe in the back end of the interior as well. For the moment, though, there was one thing I thought would be worth trying: A rear strut tower brace.

    Since I'm going with the local BMWCCA chapter next week to SD to enjoy some challenging mountain roads, I thought this would be a good opportunity to slap something together that might help.

    One of the biggest (and most complicating) requirements I had was that it must be easily removable, and cannot impinge on cargo space. Having a semi-permanent bar would make having a Touring pointless for me, since I am CONSTANTLY hauling around junk that requires me to fold down the seats. So I needed a bar that would be stiff enough to hopefully have some effect, but be easily removed in just a few seconds.

    Here's what I did.

    My temporary metal shop set up in the driveway today (garage is under construction...a whole different story )


    Some 3/16" plate steel I used to make the tower plates:

  2. #2
    Join Date
    Dec 2003
    Location
    Lincoln, NE
    Posts
    559

    Default

    You can see that I welded 2 sections together, then cut out the holes for the towers and drilled the holes for the strut mount bolts. Please forgive the shaky hand on the cuts, I will say that plasma cutters are my new favorite tool, but I have a lot to learn about making good-looking cuts with them.


    Now, I had some tube stock that I cut down to make a smaller diameter...you'll see why in a moment. First I cut:


    Then I pinched it down to the smaller diameter, welded it shut, ground it smooth, and got it to fit nicely inside the diameter of the regular tube stock.

  3. #3
    Join Date
    Dec 2003
    Location
    Lincoln, NE
    Posts
    559

    Default

    These smaller diameter tubes were welded to the plates, which can then slide into the larger-diameter tube stock as shown here (this is just tacked together)


    Then I drilled holes for quick-release pins to go through both the small and large diameter tube on each side like so:


    Next I cut the center bar in half and welded a bolt and washer to either side so that I could create a tensioning mechanism in the center of the bar. This enables me to shrink the bar down to install/remove it from the stubs, and then expand it to tighten it between the strut towers and remove any slop in the pins:



    Here you can see what the plates look like installed with just the small diameter 'stubs' protruding into the cargo area (one of these stubs was cut down about an inch after the picture, so it's even less intrusive):

  4. #4
    Join Date
    Dec 2003
    Location
    Lincoln, NE
    Posts
    559

    Default

    And here with the bar installed:


    [disclaimer] I know, I'm not a great welder. And no, the center tension mechanism doesn't work real great. I need to re-work that a little, though it's already much better than pictured, as I came up with a better nut-washer arrangement.[/disclaimer]

    So, how does it work? Well, I just ran out to dinner with my wife, and the car isn't fully re-assembled yet (plus I haven't really thrashed the car yet) but so far I'm impressed. Less squeaks, creaks, and rattles from the back end, and generally a more 'connected' feeling back there, especially over uneven and broken pavement...which pretty much all of it is here.

  5. #5
    Join Date
    Dec 2006
    Location
    Montreal
    Posts
    2,499

    Default

    it's a cool project - but if it breaks, while you are in the car, it could be very very dangerous - just keep that in mind.

  6. #6
    Join Date
    Dec 2003
    Posts
    1,640

    Default

    uh...why would it break?
    Bellevue WA
    90 535iM - not much stock remains. 3.7 liters, ported head, cammed, 3.73 diffy, M5 brakes, MAFed, yadda yadda yadda
    86 Porsche 951 - Track Toy

  7. #7
    Join Date
    Dec 2003
    Location
    Lincoln, NE
    Posts
    559

    Default

    I guess if I got t-boned by a train, having it break would be a concern...though not my primary one. It's not like I'm pre-loading it with thousands of pounds of force, so if the chassis really is moving enough to make it explode, I think I have other problems.

  8. #8
    Join Date
    Dec 2006
    Location
    Montreal
    Posts
    2,499

    Default

    Quote Originally Posted by Jeff N.
    uh...why would it break?
    you've never seen a strut bar brake? in particular a home made strut bar?

  9. #9
    Join Date
    Dec 2003
    Location
    Lincoln, NE
    Posts
    559

    Default

    I've never seen one break or brake. Though I have to admit, seeing someone brake with an STB would be cool. I admit my 2-piece unit would be more risky than a 1-piece, as a 1-piece should just bend...but either way, it's mild steel, not CF or something brittle.

  10. #10
    Join Date
    Jul 2006
    Location
    Twin Cities, Minnesota
    Posts
    71

    Default

    I'd be tempted to use some sort of mechanism similar to a chain load binder. As long as it is in compression, not tension.

    If this is a initial piece that you are using to work out the bugs prior to the "show" piece, you may think about putting the nut/bolt on end of the bar and not the middle where you would want to minimize flex. And you could take it out by dropping only one seat out of the way.

    I have taken out the screen roller thingy that sit in that same spot due to the amount of time that I was taking it in and out to haul things. I am curious how much it contributes to the rigidity of a touring? Did you think about building a brace that clips into and out of that position? Or is it too far from the struts to make a difference?

    An Interested Touring Owner,

    Fin

Page 1 of 3 123 LastLast

Similar Threads

  1. strut tower brace
    By arizona coyote in forum 5 Series BMW
    Replies: 42
    Last Post: 07-29-2008, 09:18 PM
  2. strut tower brace?
    By MaloventEvil in forum 5 Series BMW
    Replies: 15
    Last Post: 09-13-2005, 11:39 AM
  3. strut tower brace(s)
    By bahnstormer in forum 5 Series BMW
    Replies: 24
    Last Post: 01-15-2005, 04:46 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •