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  1. #1
    REG Z8 01
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    Calling Grease Monkey

    We need you now...

    Z8 Design Flaw - Details at McFly's site

    Can you give us your valued opinion and suggestions?

    REG Z8 01
    Silver/Black


  2. #2
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    Re: Calling Grease Monkey

    To begin with, everyone should read MacFly's post on this subject on his web site BMWZ8.US. If, as has been alleged, there is a design flaw in the chassis of our cars, I believe BMW will recall all of the cars and provide a reinforcement upgrade to eliminate the problem.

    You should know that the front frame rail/wheel housing assembly can be replaced in a Z8 without the need for a new frame. The old one is cut out and a new one is welded in place, something best handled by one of BMW's Aluminum Repair Centers. I assume BMW would re-engineer this part to prevent the deformation problem from occurring in the future. The deformation of the rear shock mounts would most likely require a reinforced mounting plate which I believe could be installed without major disassembly of the car. I do not believe the main frame has been affected in this case since it is heavily reinforced in this area.

    This kind of deformation is not unique to the Z8. Many cars have experienced similar problems in the past, including a number of BMWs, the 3 Series in particular. I have always wanted to install a front strut brace in my Z8 but could never figure out how to clear the plenum chamber. I believe a properly engineered strut brace would have prevented this problem and may be part of BMW's solution. Because the shocks and springs are mounted on an angle inclined towards the car's centerline, upward forces have an inward component and a good strut brace will resist those forces by tieing the opposing towers together. A properly engineered strut brace will also reinforce the shock and spring mounting area, thereby resisting deformation. It may require a redesigned plenum to accomodate a strut brace and I hope BMW does this regardless of any other fix they come up with (reinforced frame rail/wheel housing assembly).

    Besides the visual clues shown on MacFly's web site, I think a good alignment shop would be able to diagnose the problem and it wouldn't hurt to have yours checked, if for no other reason than to establish a base line for future reference. If your car's suspension is within spec, I doubt you have incurred any damage.

    Unfortunately, my "driver" is at Dinan's getting "breathed upon" so I can't do a visual inspection and my other Z8 is essentially brand new so it can't have the problem. My recommendation, at this point, would be to be cautious in your driving or store the car until BMW announces a fix. It may require the same amount of work in either case (damaged or not), but since we don't know what that fix will be, I'd err on the side of caution. I believe BMW will stand behind their flagship and restore our beloved cars to proper working order. Any talk of lawsuits is premature, in my opinion.
    Grease Monkey

  3. #3
    R. D. Linton
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    Re: Calling Grease Monkey

    Assuming you could add a strut brace and did so without strengthening the shock towers themselves, could not the forces being brought to bear by the former exacerbate the stress to the latter.

  4. #4
    R. D. Linton
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    Re: Calling Grease Monkey

    Additionally, as time goes along and miles add up, might not presently undamaged cars be more inclined to aluminum fatigue and, hence, more susceptible to shock tower deformation (and potentially breakage) in the event of a sizeable impact event?

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    Re: Calling Grease Monkey

    If a strut brace is used to solidly connect the two towers, the forces involved will be resisted by the coupling, not amplified. It's the same reason a tripod is more stable than a monopod: forces applied to one leg are resisted by the coupling with the other legs. Moreover, the forces transferred from one side of the car to the other are pushing in the opposite direction from the original forces so they counteract those forces as opposed to increasing their effect. This is the reason race cars are heavily cross-braced so they can withstand the extreme forces their chassis' must endure.

    Strut tower deformation or collapse is actually a common problem when street cars are subjected to unusual stresses, such as those experienced while racing or rallying. When Carroll Shelby began racing his early GT-350 Mustangs, they experienced frequent strut tower deformation and the problem was eliminated by the addition of a strut tower brace. Even better is the use of a triangulated brace which not only ties the two towers together in direct opposition but adds another brace running from each shock tower to the cowl area. This triangulated bracing resists chassis flex in all directions, not just side to side, and is what you'll find in most race cars.

    The reason all of this is necessary is because on most front engined cars, there is a big hole in the chassis where the engine and radiator reside. This makes it difficult to build in cross braces and inevitably results in the weakest portion of the frame located where the biggest suspension forces are being transferred to the chassis. The passenger area has the floor and roof to couple the two sides and the rear end has lots of opportunities to connect the two sides together. At an extreme level like F1, the engine is solidly connected to the chassis (no rubber engine mounts) and thus becomes a stressed member, i.e., a brace.


    Grease Monkey

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    Re: Calling Grease Monkey

    I'm not quite sure what you're driving at here. Aluminum is somewhat elastic by nature and tends to return to its original shape if deformed. If it's frequently flexed or flexed beyond its recuperative ability, it will be weakened and may fail structurally. My understanding of the current situation is that mileage does not appear to be a factor in determining which cars experience the deformations. If this is true, I see no reason to believe that the cars are deteriorating under normal driving conditions. However, I am basing my opinions on the information provided on MacFly's website thus can only speculate as opposed to offering a definitive answer.Grease Monkey

  7. #7
    R. D. Linton
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    Re: Calling Grease Monkey

    Given that the flex of the aluminum could be lateral, vertical or longitudinal or any combination of the foregoing, a strut brace could help to ameliorate, hurt or have no effect upon the situation. In any event, however, assuming an engineering defect (design and/or materials), it would appear that, to a greater or lesser extent, all cars that have been driven will have some degree of damage which is almost certainly sure to be exacerbated by further movement and, assuming this, will be particularly exacerbated by specific types of movement. In short, if the problem is caused by another other than a materials problem in a few cars, such situation is genuinely complicated and difficult and a permanent solution appertaining thereto entailing not only fixing/removing existing but preventing future damage might be more complex than at first one might like to recognize or could imagine. The good news, however, is that engineering solutions are possible but one might like neither than the cost in time, money or aggravation and the modification required might affect the value of the vehicles.

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    Re: Calling Grease Monkey

    I can only speculate as to the problem involved but it appears to be a classic case of shock tower collapse/deformation and a properly engineered strut brace coupled with reinforcement plates is the standard remedy. I cannot imagine any way in which a strut brace could exacerbate this or any other flex problem. My point is this does not appear to be a mysterious phenomenon which puts the integrity of the entire chassis in question. In my experience, the simplest explanation is generally correct (Ocham's Razor). I also see no reason to assume all Z8s have been affected. This type of damage generally occurs when certain structural integrity limits have been exceeded and as long as those limits are not exceeded, there should be no damage whatsoever. If the limits were low enough to be exceeded during normal driving, we could expect to see obvious damage across the board, with higher mileage cars showing the most. The evidence I have seen does not support this theory.

    It could also turn out that a batch of aluminum components was defective in some way and the problem will be limited to vehicles made from those parts. In this case again, other vehicles would not be at risk.

    Given the number of cars involved, I am confident BMW's Engineering Department has already come up with a solution and it will be announced shortly. My guess is they will provide some sort of strut brace and reinforcement plates for the shock towers of cars which have not suffered damage. Z8's with structural damage may require
    replacement of the front frame rail/wheel housings or possibly a complete chassis replacement. Again, this is just me speculating based upon the available information and my practical experience building race cars.

    I think we should all take a deep breath and wait for the guys in the lab coats to resolve the problem. In the mean time, I think it is important to keep this thing in perspective and not blow it out of proportion. Your Z8/Alpina is not dead; it just needs a little corrective surgery. Will that make it worth less? Ask Tiger Woods or Pamela Anderson! Grease Monkey

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    Re: Calling Grease Monkey

    When trying to determine if your Z8 has been affected by this problem, it has been suggested elsewhere that you should look to see if the gap between the sides of your hood and the fenders tapers towards the front of the car. While this may be a valid technique, I must warn you that my 2003 Z8, with only delivery miles on it, shows a noticeable taper of the gap towards the front of the car. Most importantly, the taper is symmetrical on both sides which leads me to believe it is related to assembly tolerances rather than evidence of damage. If the taper is asymmetrical or extreme, then it may be related to shock tower damage, but I don't believe this is a definitive test. I do think a noticeable crowning of the top center of the shock tower is a valid indicator of the problem since that area should have an essentially flat plateau rather than a dome shape. Grease Monkey

  10. #10
    harvey2
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    Re: Calling Grease Monkey

    I agree with your view of things, with the exception that if indeed BMW is doing anything about this at the moment (what evidence is there of this and what would their motivation be?), my experience is that it takes a lot longer than a few weeks. I would guess it will take a year.

    harvey2

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    wise words

    I am sure BMW will resolve this. Lets remember what's truly important in life and not blow this out of proportion.

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