Results 1 to 8 of 8

Thread: Torsional Rigidity numbers

  1. #1
    Sport Button On - DSC Off
    Join Date
    Apr 2005
    Posts
    125

    Torsional Rigidity numbers

    Does anyone here have measurement results for torsional rigidity of the Z8 and for the E39 M5? I recall seeing them somewhere and can't find it now. Also, are there any other specs or test results relating to frame flexibility of the Z8? I just want to win an argument and need some facts.

  2. #2
    Team Z8 RRZ8's Avatar
    Join Date
    Nov 2006
    Posts
    417
    What's the bet? Z8 stronger...?

  3. #3
    I do remember that there were numbers for that from years ago, but would have no idea where to find them now. What I remember is that there is no flex at all in the aluminum structure, and that the torsional rigidity is very high indeed compared to steel framed cars. I am pretty sure that the same is true of the Lotus and the Corvette which share relatively similar chassis concepts. I know from doing over 30,000 miles in my 4 different Z8's that there is absolutely no cowl flexing or body movement even over California's horribly rough roads, the structure is absolutely solid.

    The problem is that aluminum is rigid until it isn't, when it becomes 'exhausted' it simply fails. This has been well documented with the Porsche 928, especially in the short lived GT race series with those cars, and is a known issue in all aluminum airframes, which is why they only have limited number of take off and landing cycles in their design life.

    Aluminum is strong, but not invincible, it needs to be respected and protected, especially in the area of the front shock tower mountings of our cars. It is because of this that I really encourage all our owners to do away with the stiff and heavy run flat tires, fit the PP, and add the Alpina suspension.
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  4. #4
    Team Z8 ZMates's Avatar
    Join Date
    Aug 2009
    Posts
    393
    from: http://www.bmwz8.us/pdf/Z8_technical_in_German.pdf

    Karosseriestruktur: 230 kg
    Rohkarosserie: 275 kg
    statisch: Torsion 10500 Nm/degree
    dynamisch: Biegeeigenfrequenz 21 Hz (Gesamtfahrzeug)
    Torsionseigenfrequenz 23 Hz (Gesamtfahrzeug).

    Don't ask me how those are measured

    Silver/black
    Dinan S2 package: headers, throttle bodies, oversized MAFs, airfilters, anti-roll bars, lightweight flywheel
    Dinan by Brembo brake kit and monoball control arm bushings
    BBS forged individual wheels
    Quaife differential, 3.64:1 final drive
    Meisterschaft GT titanium mufflers
    K&W 3 way adjustable competition monotube dampers and monoball adjustable mounts
    CDV delete

  5. #5
    Z8Mania
    Guest
    I like that Andrew: Respect & Protect!

    From my seat of the pants experience: at the time the Z8 came out it was the most rigid convertible I'd ever driven and it was almost the most rigid car I'd ever driven. As the years have moved on and as the roads around me have deteriorated and other cars have gotten stiffer, I can say the Z8 does exhibit some flex, but its still pretty good. I'd say its on par with most high end convertibles of today.

  6. #6
    Team Z8 tomfakes's Avatar
    Join Date
    Sep 2005
    Posts
    358
    Since I had my center stack replaced under warranty, my dashboard has creaked over rough roads, and when cornering. It's not a lot, but it is noticeable. I haven't cared enough to get this fixed - it's been so long, that I'll need to pay my guy to take it apart and re-attach everything correctly. So there is a little flex in the chassis that can be uncovered by a slightly loose dashbaord

  7. #7
    The plastic in the center console has creaked in all the Z8's I've driven, that endless noise is one of the only things I really dislike about my car.
    Andrew Macpherson

    Expert Z8 Inspections, with full support for both Z8 sale and purchases.

  8. #8
    Team Z8 tomfakes's Avatar
    Join Date
    Sep 2005
    Posts
    358
    Mine only creaked after the electronics were replaced under warranty a number of years ago. I guess mine was a good one until that point