Page 1 of 2 12 LastLast
Results 1 to 25 of 30

Thread: Strut Braces

  1. #1
    Join Date
    Nov 2013
    Location
    West Midlands, UK
    Posts
    8
    My Cars
    1997 BMW Z3

    Strut Braces

    A kit car manufacturer that uses the Z3 as a base has started to sell strut braces starting with a brace for the rear strut towers - details here - www.bertinigt25.com/z3-braces.html

    No affiliation

    Cheers

    Ash

  2. #2
    Join Date
    Sep 2005
    Location
    Boiling Springs, PA
    Posts
    5,883
    My Cars
    '02 Z3 3.0i 5 speed
    Interesting. I'd like to see photos of it installed.

  3. #3
    Join Date
    Aug 2010
    Location
    Columbia, Worst Carolina
    Posts
    2,971
    My Cars
    2000 M-Coupe, 1994 SE-R
    Kind of hard to have a rear strut brace without rear struts.


    (Fully comprehending that fact will help one realize how little benefit a brace like this provides.)
    Last edited by BenFenner; 05-28-2015 at 11:53 PM.

  4. #4
    Join Date
    Sep 2008
    Location
    Oregon
    Posts
    127
    My Cars
    '00 Z3M / '91 318is
    I got in touch with the guy behind this venture today - he says that they're a month or two out from having a lower rear brace and front brace as well, for both 4 and 6-cyl models. Once they're all available I'll probably try those two out.

    Apparently the rear strut is available on eBay (US) as of today. I don't have the link, but its 114 shipped to USA.

  5. #5
    Join Date
    Nov 2013
    Location
    West Midlands, UK
    Posts
    8
    My Cars
    1997 BMW Z3

  6. #6
    Join Date
    Jun 2011
    Location
    Springfield, Ohio, USA
    Posts
    1,233
    My Cars
    1998 Z3 Roadster
    I'm not sure I see the point of a rear strut brace. It would be installed at the top of the shock towers a few inches behind the big cross beam. That might stiffen the chassis a little, but not much.

    Then attached to those points are rubber shock mounts connected to flexible shocks attached to pivoting Rear Trailing Arms attached to a rear subframe mounted on rubber or polyurethane. Literally everything attached to those points is flexible.

    If anything, I think this might add a little weight to the rear of the car while lightening the driver's billfold.
    Last edited by Blacklane; 05-29-2015 at 08:33 AM.

  7. #7
    Join Date
    Nov 2013
    Location
    West Midlands, UK
    Posts
    8
    My Cars
    1997 BMW Z3
    I don't have one, just thought I would share, the guy's theory was it is an empty market and the butt-strut is very expensive for what it is - hence he is planning to make his own lower strut as well and market them. (Particularly if you are shipping outside US as then you have taxes etc.)

    Alot of the feedback on these products can be simply placebo.. apparently It improves the looseness of the Z when cornering - I'm sure polybushing the subframe offers more than anything else

    Ash

  8. #8
    Join Date
    Oct 2011
    Location
    Arkansas, USA
    Posts
    1,281
    My Cars
    95 240SX|98 Z3M|05 Elise
    Quote Originally Posted by BenFenner View Post
    Kind of hard to have a rear strut brace without rear struts.


    (Fully comprehending that fact will help one realize how little benefit a brace like this provides.)
    Quote Originally Posted by Blacklane View Post
    I'm not sure I see the point of a rear strut brace. It would be installed at the top of the shock towers a few inches behind the big cross beam. That might stiffen the chassis a little, but not much.

    Then attached to those points are rubber shock mounts connected to flexible shocks attached to pivoting Rear Trailing Arms attached to a rear subframe mounted on rubber or polyurethane. Literally everything attached to those points is flexible.

    If anything, I think this might add a little weight to the rear of the car while lightening the driver's billfold.
    It's absolutely true that there are no rear struts. So, let's agree for the purposes of this thread at least, to mentally substitute "shock tower" for "strut tower".

    First I have questions about the mounting and flex concerns. I am sure we have all seen many strut tower bars that mount along the front of a car's shock/strut towers. Most of them mount to the same bolts that hold the shock/strut. These bolts pass through the towers and this locates the bar. Aren't most bushings in this application more centered around the shock shaft, and not the mounting bolts? In short, having seen Mr. Cherry's product pictures, I do not see how the mounting mechanism and presence of bushings is any different than any other similar product.

    Next, despite having no actual struts, does that instantly mean that there are not similar forces at play? Additionally, there are many cars with factory double wishbones type setups that also include shock tower bars--from the factory. Are we to believe that the manufacturers are just idiots for putting a bar there, or are we to believe that there is a valid purpose, even in the absence of a strut? Let's consider these two issues for the Z3 in particular. First, I have had a hard time finding the rear upper control arm. So, when we take a corner, there should be a twisting force around the lower control arm, and no upper arm is there to help offset that force. The twisting would come mostly from momentum trying to push the car to the outside of a corner, directed through the center of the wheel. Opposing that is friction from the tire, allowing us to move in to the corner, but since the friction happens at the bottom of the wheel, there is a twisting force around the wheel. The lower arm is split to two mounting points and I am guessing that will accept most of that twisting force, but at least from my simplistic view, it would seem some of that force could also push the shock outward during a turn. If it didn't, we probably wouldn't have a need for upper shock bushings, right? The shock mounts would then transmit that outward force to the shock tower. A shock tower bar would spread some of that force to the other shock tower and reduce overall chassis flex, right? The other consideration is that we encounter vertical forces, such as a bump in the road. This pushes up on the shock, and through the shock mount, thus pushes up on the shock tower--the body of the car. I think this force is the reason that car manufacturers have seen benefit to adding a bar to a double wishbone. The bar car again spread the force, this time more vertical, across both sides of the car, still reducing overall chassis flex. Particularly in the design of Cherry's bar, note that it is not "hinged" as some strut tower bars are. This should help with the vertical forces, right?

    I am not saying that I am 100% correct here, but rather, looking at it with my tiny little mind, I can see some reasons that this product may still provide a benefit despite the lack of struts and the presence of bushings.
    Last edited by Scarceas; 05-29-2015 at 10:42 AM.

  9. #9
    Join Date
    May 2013
    Location
    USA
    Posts
    441
    My Cars
    2001 Z3 3.0/5 roadster
    No cuteee holes in carpet. Now, windshield wiper arm stress bar to reduce cowl shake, maybe.

  10. #10
    Join Date
    Dec 2005
    Location
    Sarasota, FL
    Posts
    7,558
    My Cars
    98 M Roadster
    The rear shock mounts do not see side-to-side forces. The shocks are "soft-mounted" in the RSMs at the top and whatever bushing is in the lower mounting point. They are there to dampen the spring. That's all. The only forces that area of the body sees from the shock is up/down.

    The front end is a completely different story, since the spring (effectively) sits between the hub and body at the upper strut mount. That makes that strut tower a major load-bearing structure and somewhat more prone to movement relative to the other side, since there is nothing in between them at the top.

    The rear brace looks nice, and I think it's great that someone is making new products for the Z, but it's not going to perform a function beyond that.

  11. #11
    Join Date
    Oct 2011
    Location
    Arkansas, USA
    Posts
    1,281
    My Cars
    95 240SX|98 Z3M|05 Elise
    Quote Originally Posted by Vinci View Post
    The rear shock mounts do not see side-to-side forces. The shocks are "soft-mounted" in the RSMs at the top and whatever bushing is in the lower mounting point. They are there to dampen the spring. That's all. The only forces that area of the body sees from the shock is up/down.
    If there are no horizontal forces, would there be a need for the shock mount bushing to surround the shock? Why even have a bushing there at all, then? Also, what benefit is there to a fully metal mount such as this:
    http://store.bimmerworld.com/bimmerw...unts-p104.aspx
    Also note their claim that "with the typical performance rear shock mount you are getting approximately 1/2" of uncontrolled movement as the upper shaft mount flexes".

    Surely there are some horizontal forces at play?

  12. #12
    Join Date
    Jun 2011
    Location
    Springfield, Ohio, USA
    Posts
    1,233
    My Cars
    1998 Z3 Roadster
    I always thought the biggest force on top rear shock mount is the change in angle of the shock as the Rear Trailing Arms move up and down. For the same reason, the lower shock mount is a pivot that is parallel to the Trailing Arm pivots. That would make it a rotational force. That force would have little effect on handling, but would tend to fatigue metal in the shock towers leading to early failure.

  13. #13
    Join Date
    Jan 2012
    Location
    Vancouver, WA
    Posts
    627
    My Cars
    2000 M Roadster
    OK where to start

    In a McPherson strut setup moving the top of the strut inward or outward changes the steering geometry.(camber and toe to a much less of a degree) This is because the axle/spinal is mounted on the strut and moves in conjunction with this movement. This can be proved by swapping hats and using/installing camber plates. see exhibit A. The flex point is in the ball joint below the spinal.

    Exhibit A


    Now our Rear trailing arms do not change the geometry if you move the angle of the shock in any direction. The only way to change adjust camber or toe is to move the position of the rear trailing arm bushings. see exhibit B

    Exhibit B



    Note: The rear axle runs through the bearing in the rear trailing arm. The shock pivots top and bottom and does not effect the geometry at all.


    As to the movement referred to in this statement

    "Your dampers should precisely control all suspension movement, and with the typical performance rear shock mount you are getting approximately 1/2" of uncontrolled movement as the upper shaft mount flexes and moves. Average road surface imperfection rate of change means you are giving up a lot of control and potential grip. You paid for that shock - put it to work!"

    It is solely talking about rebound and dampening. That would be the flex in the rubber part of this mount as the body moves up and down not side to side.


    MY CONCLUSION

    I do not see any way that a rear shock brace could do anything for OUR rear suspension.

    - - - Updated - - -

    As to the reason some manufactures add a shock/strut tower support bar to a ddb wishbone suspension:

    In the photo below note that the upper wishbone is mounted to the sheet metal in the strut tower. In this case a tower support bar will minimize inward and outward movement in the tower where the upper pivot point is.



    Our rear trailing arms only have 1 pivot and it relies on the 2 RTAB's to create that pivot point. The carrier bearing and axle are ridged mounted to the trailing arm, the spring provides trim height and the shock dampening.
    Last edited by Tib; 05-30-2015 at 06:38 PM.

  14. #14
    Join Date
    Feb 2014
    Location
    O.C. Oregon
    Posts
    1,058
    My Cars
    E36-E367-E39-E53
    This guy had a post with a pic anouncing the start of sales. Looks like it may have deleted?

    The pic showed it mounted, looked to be right behind the seats, where there is a large piece of sheet metal running across the entire length and then the bar laying over that. ?
    ​~Mike


  15. #15
    Join Date
    Oct 2011
    Location
    Arkansas, USA
    Posts
    1,281
    My Cars
    95 240SX|98 Z3M|05 Elise
    Quote Originally Posted by HeliHover View Post
    The pic showed it mounted, looked to be right behind the seats, where there is a large piece of sheet metal running across the entire length and then the bar laying over that. ?
    I think you just won the thread.

    Attached Images Attached Images
    Last edited by Scarceas; 05-30-2015 at 11:54 AM.

  16. #16
    Join Date
    Jan 2012
    Location
    Vancouver, WA
    Posts
    627
    My Cars
    2000 M Roadster

  17. #17
    Join Date
    Oct 2004
    Location
    here & there
    Posts
    4,715
    My Cars
    01 LSB 367M
    Interesting and looks to be well made, however, I too don't see any benefit to be gained. If anything, it will cause problems with your top/rear window if you go topless often.

    2001 S54 LSB/NAPA. 1 of 7.

  18. #18
    Join Date
    Jul 2006
    Location
    CA
    Posts
    1,350
    My Cars
    02 E36/8
    if in fact these add no functionality to the car, why have they made them for e36s including the compact? i guess some people just like adding things to their cars to be cool ( think honda's with c-pillar brace)
    Last edited by ZoO; 06-02-2015 at 06:21 PM.

  19. #19
    Join Date
    Oct 2004
    Location
    here & there
    Posts
    4,715
    My Cars
    01 LSB 367M
    Or the butt strut... but that's a dead horse. It's your ride, your money. Do whatever you like, just don't expect everyone else to follow suit and give standing ovation.

    2001 S54 LSB/NAPA. 1 of 7.

  20. #20
    Join Date
    Mar 2014
    Location
    Minneapolis
    Posts
    150
    My Cars
    2000 Z3 2.3 & 14 allroad
    I guess we see now why it's such an "empty market".

  21. #21
    Join Date
    Jul 2011
    Location
    Here
    Posts
    918
    My Cars
    '01 SG/IR S54 M Coupe
    it would stiffen the body up a bit, but not enought to notice without instrumented testing/K&C machine.
    If they call it Tourist Season, why cant we shoot them?

  22. #22
    Join Date
    Aug 2010
    Location
    Columbia, Worst Carolina
    Posts
    2,971
    My Cars
    2000 M-Coupe, 1994 SE-R
    Quote Originally Posted by Bcar View Post
    it would stiffen the body up a bit, but not enought to notice without instrumented testing/K&C machine.
    The first (only so far) non-OEM owned kinematics machine has been in operation for a few years now and they still haven't found a benefit to any aftermarket strut tower brace, let alone a shock tower brace. They are like the goggles.

  23. #23
    Join Date
    Jul 2011
    Location
    Here
    Posts
    918
    My Cars
    '01 SG/IR S54 M Coupe
    it would stiffen the body up a bit, but not enought to notice without instrumented testing/K&C machine.
    If they call it Tourist Season, why cant we shoot them?

  24. #24
    Join Date
    Sep 2013
    Location
    Fort Lauderdale, FL
    Posts
    985
    My Cars
    e30 m3, 99 M Roady
    Quote Originally Posted by BenFenner View Post
    The first (only so far) non-OEM owned kinematics machine has been in operation for a few years now and they still haven't found a benefit to any aftermarket strut tower brace, let alone a shock tower brace. They are like the goggles.
    more info on this?

  25. #25
    Join Date
    Aug 2010
    Location
    Columbia, Worst Carolina
    Posts
    2,971
    My Cars
    2000 M-Coupe, 1994 SE-R
    Quote Originally Posted by ADAz3M View Post
    more info on this?
    http://www.caranddriver.com/features...g-it-tech-dept

    Simons adds that he’s never seen an aftermarket strut-tower brace provide a measurable handling benefit.

Page 1 of 2 12 LastLast

Bookmarks

Posting Permissions

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