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  1. #1
    rjay
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    GM---please use your influence

    As you discussed in an earlier post:
    My Z8 has been checked. (348 views) (901 thread views)

    Message: My "driver" Z8 is at Dinan's shop awaiting its new power plant so I have been unable to check it over for deformation damage. Steve just e-mailed that the car is perfectly straight. What's of more interest to others, that car has app. 18,000 miles on it and has been driven hard. Along the way, it has encountered any number of pavement irregularities at high speeds, has bottomed out the suspension crossing railroad tracks, plus it has the reduced travel and stiffer spring rates associated with the ACS suspension kit. This leads me to believe the cars which have reported damage either have defective parts or have sustained a pretty radical "hit" somewhere along the line. The point is, at least in my case, the Z8 remains a very robust automobile capable of handling most driving situations with no resultant damage.

    Steve Dinan also said they have a spare Z8 chassis in house and he believes they can engineer a prophylactic fix which might be an alternative to whatever BMW comes up with. I fully expect BMW to offer a properly engineered solution but it's nice to know that Dinan feels the problem can be readily solved.

    One other point: it has been reported elsewhere that the latest generation 5 and 6 Series BMWs have experienced similiar deformations so the problem may not be unique to the Z8. I have no way to confirm this information but if true, it does offer hope that BMW's response will be swift and thorough.
    Grease Monkey


    At this point, I hope you can convince Steve to at least consider the problem and see what he can do about a fix, whether its billed as a "performance" stiffening mod or anything else. I called Dinan and got a very uncertain reply as to whether they will even consider working on the issue, for a host of reasons, developoment cost vs sales oppty, liability, bmw relations, etc. It would be very helpful (but dissapointing) just to have Dinan say there is no reasonable fix at a reasonable cost, at least then we know what paths to pursue.


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    Re: GM---please use your influence

    I have already asked Steve Dinan to get involved and I am waiting to hear back from him. I am convinced that the shock tower deformation problem can be prevented through the use of an internal reinforcing plate and a strut brace. If Dinan declines to pursue this, I believe there are some other options available to us.

    My driver Z8 has app. 18,000 hard miles on it with no shock tower deformation. I have encountered any number of abrupt road breaks at high speeds and have bottomed out the suspension on railroad crossings, so my car has certainly experienced potentially damaging input. Add to this the fact that my Z8 has the ACS suspension kit installed which reduces suspension travel and increases the spring rate and it would seem that my car should be very susceptible to the problem. If we assume that all Z8s have the potential for shock tower deformation, as opposed to limiting the damaged cars to ones which may have been assembled with an inferior batch of aluminum (still a possibility in my mind), then the most likely explanation for my car's lack of damage is the fact that it has reinforcement plates installed in the shock towers. Yes, I have Dinan's caster plates installed in the front shock towers and those plates add substantial reinforcement to the top of those towers. In fact, those 1/4" thick plates would have to bend before the shock tower could follow suit. If we add in a strut brace to prevent any frame flexing between the towers, I feel confident that the problems being reported can be avoided altogether.

    There are some things to consider in this approach. The Dinan caster plates raise the car's ride height up front by that same 1/4" so the car's rake will be different than a stock car's. I don't know if this would create a problem with the front end lifting at high speeds but it must be considered. Of course, if plates of similiar thickness were added to the rear shock towers the net result would be neutral. However, then we must consider the affect of raising the overall ride height by that 1/4". In my experience, the Z8 handles much better when its ride height is lowered so I don't like the idea of moving in this direction. On my car with the ACS kit, the car's ride height has been lowered considerably and I always thought the front was a bit too low, so the Dinan plates serendipitously evened things out. Since it appears the ACS kit is no longer available, duplicating my set-up may be impossible but ACS might be convinced to resume production if there was a strong demand. As an alternative, it might be possible to find another company to produce camber/caster plates for the front and reinforcement plates for the rear in a package which includes slightly shortened springs. This would provide stock ride height and reinforced shock towers. Then if we can find a company to produce a properly engineered strut brace, I think the Z8s so equipped would be well protected from any potential damage. Keep in mind that the reason no one has done a strut brace for the Z8 so far is because clearance above the plenum chamber is virtually nill with the hood closed so it might mean a notched plenum chamber to accomodate the strut brace would have to be part of the package.

    Of course, Dinan could easily supply all of these parts in a properly engineered kit and I hope they will do so. They already have the front caster plates and the proper lowering springs, so they just need to figure out the strut brace and make up some rear reinforcement plates. In the mean time, anyone wishing to act prophylactically could just install the Dinan suspension kit (caster plates, lowering springs, adjustable anti-roll bars).

    Where does all this leave those owners whose cars have already suffered shock tower deformation? I have been in contact with one such owner and he has provided me with a detailed alignment report on his Z8. The most interesting thing contained in the data is that his car, which has visible shock tower crowning on one side, is comfortably within the factory's specs in all respects except for front camber where both sides are near the high end of the negative range. This is exactly what I would expect to find on a car which has had some shock tower deformation. On the bright side, the deviation was quite minor (and still within factory spec) and the change was in a good direction for improved handling! Since front camber is not adjustable on the Z8 (except by lowering the car which increases it in the negative direction), it is virtually impossible to increase negative camber any other way. So, if the situation remains stable, his Z8 will benefit from the increase. If he wants to prevent the possibility of further change, or return to stock settings, I believe the top of the towers could be flattened and then reinforcment plates could be installed. Please remember that when the camber changes, so does the toe-in on the car, so a full alignment is required to get everything right. I encourage everyone with a Z8 to have a full alignment check done at a competent shop, whether you think your car has suffered damage or not, just to see where things are. Street driving can often knock a car's suspension out of alignment and the only reliable way to tell is to have it checked. Also, I believe an alignment check is BMW's recommended way to tell if your car has suffered substantial damage.

    Given the value of our beloved Z8s and the emotional attachment most have with them, I believe pricing will not be a deterent for most owners, so producing a reinforcement package should be a profitable undertaking for any company willing to get involved. As soon as I hear from Dinan, I will let everyone know.

    Grease Monkey

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    I agree with a lot of things you say, however,

    I am surprised how easily you recommend a couple of things:

    "In the mean time, anyone wishing to act prophylactically could just install the Dinan suspension kit (caster plates, lowering springs, adjustable anti-roll bars)."
    Strong recommendation: Go away from stock setup before BMW comes up with a fix, and use something YOU THINK may prohibit further damage.

    "If he wants to prevent the possibility of further change, or return to stock settings, I believe the top of the towers could be flattened and then reinforcment plates could be installed"
    Depending on the degree of bulging, this can be a dangerous recommendation IMO.

    Please consider the weight your words have on this board.

    I recommend that any owner with a damaged car have it repaired according to the guidelines of BMW, anything else will put the risk in your hands.

    Regards,
    Dieter

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    Re: I agree with a lot of things you say, however,

    Based on the information BMW has provided to date, they are not planning to offer a fix, so my suggestion does not preempt anything. Also, Dinan's kit is specifically warranted against causing damage to the car so I see no risk in its installation. On top of that, shock tower deformation is not unique to the Z8 and the cure on many other affected BMWs has been to add reinforcement plates to the underside of the towers, so there is already a precedent for this approach.

    Regarding your second point: I suppose there could be an extreme case where trying to flatten a tower bulge could result in catastrophic metal fatigue but I was referring to the specific car under examination which has only minor crowning. The addition of the very rigid and intimately joined reinforcement plate would transfer the load surface away from the affected area thereby relieving it of stress. In fact, even if the tower bulge was left untouched, the reinforcement plates should still act to prevent further crowning.

    While I appreciate your concerns, I am comfortable with what I wrote. As always, I am just expressing my opinion, not offering definitive proof (impossible in this forum), so it is up to each individual to make their own choice on how to proceed. At the very least there is food for thought and perhaps a way forward. Grease Monkey

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    Re: I agree with a lot of things you say, however,

    With all due respect, you should be cautioning Macfly not GM on their opinions regarding the frame issue. Macfly repeatedly refers to an unscientific sampling of roughly 50 owners to recommend that owners garage their cars and join a class action suit. Former engine builder vs. commercial photographer...hmmmmm...

  6. #6
    harvey2
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    further questions

    These are secondary concerns but I presume that a strut reinforcment design will alter the characteristics of the crumple zone during some types of collision. Can you speculate or comment on what effects the typical aftermarket strut braces have on crumple characteristics and whether a good designer can avoid degradation of the car's behavior in a collision?

    If there will be potential for ride height adjustments, I wouldn't mind a little bit off the top from my stock setup. Say perhaps 0.5 inches or so lower. Just for looks mind you.

    All opinions taken as such. Thanks in advance for your technical insights.

    harvey2

  7. #7
    Michael
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    I would also like to hear from shadowman as he

    has also heaviky modified his car in both the power and suspension department. What has he seen in his and customer cars? What kind of reinforcement do his coilovers provide?

    Another valuable source of information.

  8. #8
    rjay
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    thanks, appreciate it

    I think a fix is needed based on examining my car and reading all the posts, and I want to find one. I have 7,000 miles on a 2001. I am the second owner, bought at 2200 miles and the original owner took immaculate care of the car; it was showroom. There were no records of any alignments done by BMW or any other indication of previous damage or significant impacts by the 1st owner. I have never experienced an impact outside of very ordinary driving cirmcumstances. I have a slight narrowing of the hood "gap" on the drivers side, about 1/8 inch in the last 18 inches toward the headlight, and the shock tower on that same side, although visibly flat, is very slightly domed when putting a straight edge on it, compared to the other side. I don't know when this happened, as I only noticed it upon close inspection after the story broke. So I think I have the very beginnings of the more severe problems shown. I am very interested in finding some kind of reinforcment that can prevent further damage, because I want to drive this car for a very long time.

    I have the Dinan S3 suspension installed at about 6,000 miles, SO3's, and stock wheels. Thanks again for any "prophylaxis" you can help conjure up!

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    Re: I agree with a lot of things you say, however,

    Your statement clarifies your opinion, thanks.

    There may be a grey zone of slight bulging where the towers could be flattened again, however, it is absolutely clear that BMW prohibits any and all kind of such repair on the aluminum frame.
    So even if it would be technically possible, one would be violating BMW's repair instructions and thus take all risks and liability for the car from there on. In case of a later accident there could be an argument about this.

    I agree with your opinion regarding a reinforcement plate, several BMW cars have seen some fix of this kind lately. I personally don't see a need for a strut brace, because the towers are not collapsing, they only can't handle the vertical forces.

    Bottom line:
    If your car is damaged now, this should be covered by your insurance, because you have BMW's blessing that this must have been an accident-like situation. So the insurance must pay. There is no need to call Joey's Garage to flatten strut towers.

    As far as modifying an undamaged car goes, this is fine, it looks like the Dinan plates can improve the situation.

    Cheers,
    Dieter

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    Re: I agree with a lot of things you say, however,

    Thanks for your opinion, and I did exactly what you suggested. I can understand that emotions went up easily, especially after BMW's last response. It is good to see that the discussion has reached a new level now.

    My point here was not to question GM's capabilities as an engine manufacturer, it was all about the mandatory way of repairing such damages to not loose BMW's support in the future.

    Also, for all people commenting on this issue:
    As long as you don't have experience in designing and building aluminum space frames, as long as you don't have access to the CAD data and can simulate any suggested change, everything is speculation.
    I for my part don't have access to such data, so I don't know what side effects can appear when reinforcing/modifying certain parts of the frame.

    I personally am convinced that there will be a fix coming from BMW, but that is my opinion only, no matter what I base it on. Call it trust in a great brand if you want to.


    Cheers,
    Dieter

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    Remember the Z8 is hand built!

    It is common for the gap to narrow towards the headlight- the test is to see if its pinching in by where the wheel well is. The shock towers do have some natural crown in them so do not freak out just yet- the thing to do is what BMW and GM suggest- get an alignment done and then you will know where you stand.

  12. #12
    Robbie Robbins
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    Re: I would also like to hear from shadowman as he

    I am thrilled to see some definitive direction being taken. For me it would help if one or all of the most knowledgeable here would rewrite the suggestions in a ordered (and simple)way to go about A. assessing the current status of an owners car and then B. An ordered list of suggestions to help prevent future damage. Aftermarket mods etc. are worth considering. I'm a simple guy that could use help in the form of a decision tree. I love my Z8 and would love to keep on enjoying it, but would appreciate suggestions to lift the "fog".

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    Re: further questions

    The forces involved in a crash powerful enough to activate the crumple zones on a car would totally overwhelm the structural integrity of a strut brace. Remember, the crumple zones are designed to absorb frontal impact energy to keep it from being transferred directly into the passenger compartment whereas a strut tower brace is designed to resist side to side forces. Plus, strut tower braces have been offered as an option from OE manufacturers and from aftermarket companies for many years now without generating safety concerns.

    The Dinan suspension kit does lower the Z8 by app. 1/2" and I believe this is a good compromise between handling improvements and ground clearance.Grease Monkey

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    Re: I agree with a lot of things you say, however,

    Thanks for rushing to my defense but you should know that I have a great deal of respect for dwz8 and his points are well taken. I just wanted to move the discussion away from doom and gloom and begin to offer a possible way forward. I would also like to set the record straight regarding my automotive background. I do not have an engineering degree. I have an extensive (lifelong) background in automotive repair, modification, restoration and construction. I began as a child handing wrenches to my father while he restored antique cars, graduated to restoring my own sports cars including a ground up restoration of a 427 Cobra when I was 18, apprenticed as a high-performance engine builder under an engineer at Ford's SVO, operated a race car building business for many years, ran my own repair and restoration shop specializing in Porsches and Ferraris, and am currently acquiring and restoring '60s vintage sports cars as a hobby. Needless to say, I have also spent a considerable amount of time and effort massaging my Z8. My opinions are based on my experience. People should take them for what they're worth.

    Thanks again for your kind words. That's what I really like about this board, the sense of comraderie. Grease Monkey

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    Re: I agree with a lot of things you say, however,

    Your points are well made and your advice is sage. Just to be clear, I am not advocating taking your Z8 with bulging towers down to the corner garage and having them pound the tops flat. What I envisioned was the possibility of adding reinforcement plates to a car with deformed towers and then flattening the tops to provide intimate contact with that plate. My approach would be to use the attachment bolts to gently draw the two surfaces together thus creating a reinforced sandwich in the problem area. I realize this might void your factory warranty, though I doubt the procedure would be detectable, and I would limit its application to those cars with minimal visible damage. Since BMW has stated that there are no safety issues involved, I think this approach carries very little risk. But I am well aware of BMW's position on this matter and cannot offer any guarantees myself, so let's just call it food for thought as opposed to a recommendation.

    Another option for cars with bulging tower tops might be to fill the gap between a reinforcement plate and the tower itself with a structural resin compound to provide intimate contact without altering the deformed aluminum in any way. If there really is no safety issue associated with the deformation, perhaps this approach would be a more cost effective way to deal with the problem than resorting to replacement of frame structures. Grease Monkey

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    Excellent, and more food for thought...

    I heard about somebody who knows somebody who supposedly created two pieces of metal that would fit exactly from both sides, and that he stated that he would be able to return the top - within certain boundaries of bulging - to something flat again.

    While this is certainly not a recommended repair method NOW, it may give some engineers at BMW something to think about. Maybe the requirement for the frame exchange was established at a time when nobody expected anything to happen to a frame ever (remember, expectations were at <1%). So probably they stayed on the safe side.

    I also heard that in cases of damages on aluminum Audi some repair is allowed, again within narrow limits.

    Nothing more than food for thought, however, I like sandwiches, if they are well prepared...

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    Thanks for your kind words,

    and I certainly want to return the compliment to GM.

    It is good to have a discussion about the facts, based on experiences and real measurements.

    It may be that I am overly sensitive, but that is for the following reason:
    if you "repair" the frame in a way that is not allowed by BMW, you loose the right to drive it. Of course, you can hide this away, but in case of an accident your insurance may blame you for not following the rules and simply not pay.
    Apart from that, I am driving at 170-180 mph several times a week on the Autobahn. The idea of a collapsing/malfunctioning/disintegrating strut tower doesn't really appear to be enticing to me.

    To GM: Respect for this and a lot more posts, and I agree with your technical conclusions as said, I just wanted to prevent somebody from going to mailorder Dinan's caster plates and walk to Joey: "Hey, GM has said you can flatten it...".
    Of course, I understand that you didn't mean it this way.

    Cheers,
    Dieter

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    Re: Remember the Z8 is hand built!

    Thanks. I know that the gap naturally narrows from the windshield to the headlight, but my left side is different than the right side in the degree of narrowing in the last 18 inches towards the headlight. I could hope this is just natural "hand built" variation, but I am convinced that the shock tower crown on the same left side is not as flat as on the right side (put a straight edge on the towers and see how much it can rock side to side). Those two things together I am not willing to trust to coincidence. I will get an alignment check, but I would expect it to be normal or very close to normal, due to the slight amount of distortion, and thus a "normal" alingment is not going to allay my concerns that there is potential for further damage "down the road". I am still driving, but it's not as fun anymore, and won't be until the problem is better identified (or lack therof proven) and a fix implemented. Rjay

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