Location: Location Location NW Suburb Of Chicago, USSA
Quote:
Originally Posted by MTIRC6Z
Hard to imagine how something THAT big could get under the car to begin with...talk about bad luck!
As for whether the car would have broken similarly IF it hadn't had the coilovers...well now, there's a great reason to keep the car stock. When you're talking to your buddies tell them, "Yeah, I woulda put one of demder fancy coilover systems on my car but I didn't because I wanna be able to run over an 8x8 without doing TOO much damage.".
Cheers, Paul.
Quote:
Originally Posted by Zoxxo
Thank you!
How in the world do you drive over a "6 x 6 or 8 x 8" chunk of wood - at speed - with enough force to break the suspension - and manage to have a totally unscathed front splitter?? Something about that does not make sense at all.
Z//
As I said in the OP, it appears that I hit it with the Gurney lip and the little bit of the tire that sticks out from the painted bumper but is still behind the lip. In the words of Maxwell Smart "[Almost] missed it by that much!"
Location: Location Location NW Suburb Of Chicago, USSA
Quote:
Originally Posted by LG Motorsports
I would suspect that you will find a bent "A" arm also that bent at the location of the lower shock mount on the A arm.
...
I would also venture to guess that the failure will be found to be the bayonett (SP) top mount with rubber bushings that plunged through the top mount first, then if the shock was bottomed out, it had no where else to go but up.
Thanks, Lou - that's the kind of info I was looking for.
Quote:
Originally Posted by Aaron Pfadt
J,
First of all, sorry to hear about your incident. Glad that no-one got hurt.
This is in interesting thread because it is the first time I have ever seen an actual shock tower failure. It will only ever be speculation about whether this same failure would have occurred without coilovers being on the car. My personal feeling is the same as several of the other vendors on this thread in that probably the same thing would have occurred even with stock shocks.
The limiter of the suspension travel in all of the C5 and C6 Corvettes is the shock absorber . Clearly the impact of the wheel with whatever J hit caused an extreme wheel movement. The stock shock would have bottomed out and then likely pushed up through the frame.
Like the others on this thread, I am interested to see more pictures of the damage. Then we can resume our armchair engineering
J, let me know what we can do to help.
Thanks, Aaron. I (or someone) will certainly be in touch for various replacement parts. I certainly don't think this was caused by the Pfadts, or even by the change to coil-overs, but felt I needed to mention these things in the interest of full disclosure.
If I get a chance to get more pictures, or if Randy from DRM does stop by, we'll get those posted.
Location: Location Location NW Suburb Of Chicago, USSA
Quote:
Originally Posted by Paulg680
I know it's hard to believe but it's true. I was ahead of Just J and saw the 6X6 with my own eyes. I was able to dodge it but Just J had no where to go because of on-coming traffic. We both marveled at the fact that his car was able to get up and over the wood since his car is lower than stock. My only guess is that his right front wheel caught just enough of the wood to go up and over it. We tried to find the offending piece of wood without success. We knew that people would find this hard to believe.
Here are a few pics I took...
The nose, fender, wheel and tire were unscathed...
Thanks for the additional pictures, Paul.
And thanks again to you and your better half for hanging out with me for the 90+ minutes it took to get the flatbed there and loaded. A very classy thing to do.
I held onto two pieces of cast aluminum that I found in the engine bay directly below the shock. I took a few pics to help folks understand the failure mode involved here...
Coilovers had absolutely nothing to do with this. The driver drove over a friggin log the size of a 6x6 or an 8x8.
"Denial ain't just a river in Egypt!"
The shock, mounts were never designed to be the primary load bearing points on the suspension. If the leaf springs had been in place there is a good chance the shock wouldn't have bottomed and broken the shock mount. The impact load would have been primarily absorbed by the spring perches which were designed to withstand such impact.
This is precisely why the author of Mustang Performance, William Mathis, told me that it was mandatory that I reinforce the strut and shock towers on my '03 Cobra. Different car but same principles apply.
By installing coilovers you are dramatically altering the design of the suspension. This can be good (and very seductive) in terms of performance but disastrous in terms of safety. Unless you also re-engineer the shock mounts to withstand this type of loading and impact resistance.
Imagine this scenario: You install coilovers on your Z06, drive a combination of street and track. You hit a moderate number of bumps and a few potholes which stress and flex the shock mounts causing metal fatigue. You go out on the track for an HPDE and enter a high speed sweeper loading the suspension heavily on a front corner of the car. The mount lets go sending the wheel up and the car down - this would undoubtedly cause some control issues.
Catastrophe? Hell yeah. Possible? Absolutely. This accident just illustrates how quickly it can happen under certain circumstances.
You will many times hear people (and especially resellers of coilovers) state that they have used their products for many thousands of track miles and have had no problems. We generally don't encounter potholes and large obstacles on the track that cause heavy impact strains. However, a car that is driven on the street does see this type of wear and tear.
I'd be first in line for coilovers for the Z06 if I knew for certain that the shock mounts could be strengthened to withstand this type of loading. I haven't yet seen any evidence that they can be so strengthened and until I do this is one mod I will most definitely avoid like the plague.
Of course I have AND more importantly I've discussed this subject, at length, with an expert (who doesn't sell coilovers) on this very subject. And I installed coilovers on my '03 Cobra following his advice. These experts that you cite also sell coilovers. Think about it.
I don't see any coilover manufacturer or reseller offering a warranty or otherwise guarantee against shock mount failure.
Just J's unfortunate experience shows what can happen with a large, forceful, single impact. What if this impact was just 99% of what was necessary to cause failure - so that the mount cracked or was seriously weakened but did NOT totally fail. And what if he then went out for an open track event and went flying into several high speed turns loading the suspension up. And what if the shock mount failed during one of those high speed turns?
Clearly this is a plausible and a potentially life threatening scenario.
And it's also plausible that the cumulative stresses from much smaller impacts can eventually weaken a shock mount and set up a condition ripe for failure.
I know this is an unpopular point of view due to aggressive and successful marketing and the powerful seduction of the performance improvements of coilovers. All I'm doing is pointing out the flipside which is now clearly shown to be a real possibility.
Last edited by Exterminator; 05-26-2008 at 03:57 PM.
I can't remember which company, but it was Callaway or Lingenfelter, that would not put coilovers on the Z because the car was not designed for it. I agree with the posts that say coilovers put more force on the shock mount that it was originall designed for. It makes sense and if either one of those companies question it, that is good enough for me. If I am not mistaken, one of those companies uses a coilover system that uses a different leaf spring and coils together?
Regardless of where the spring is (coil-over or leaf) when you bottom out any shock (OEM whatever) it's going to act like a solid rod and transmit all the force up. The spring becomes irrelevant.
I can't remember which company, but it was Callaway or Lingenfelter, that would not put coilovers on the Z because the car was not designed for it. I agree with the posts that say coilovers put more force on the shock mount that it was originall designed for. It makes sense and if either one of those companies question it, that is good enough for me. If I am not mistaken, one of those companies uses a coilover system that uses a different leaf spring and coils together?
Callaway uses the stock springs in conjunction with their coilovers solution.
Quote:
Originally Posted by dagon138
Such Drama Queens.
Regardless of where the spring is (coil-over or leaf) when you bottom out any shock (OEM whatever) it's going to act like a solid rod and transmit all the force up. The spring becomes irrelevant.
Evidently you are oblivious to the obvious or maybe you just don't mind risking your car and/or your life. If the leaf springs and spring perches are carrying the load of the car then they will absorb the majority of the impact loading up to and until the shock bottoms out.
If it's "irrelevant" where the springs are, then why don't we see shock mount failures on cars without coilovers?
One thing is clear, there needs to be a separate bump stop apart from the shocks, especially if coilovers are installed.
[By the way Dagon, the Edit to add the "Drama Queen" comment didn't make your post any more convincing.]
Last edited by Exterminator; 05-26-2008 at 05:00 PM.
[quote=Exterminator;1565623558]
I don't see any coilover manufacturer or reseller offering a warranty or otherwise guarantee against shock mount failure.QUOTE]
This is the reason for no warranty. No single person can guess, engineer and or know when and how a car will take a impact, would the shock tower be ok if he only hit a 4 x 4? What could have broken if he hit a 12 x 12 or jumped the car into the ditch???
I will back down now, because I know you will be beating this one failure to death. I have a feeling that we will be hearing about this thread in later years.
Does GM or any other car company warranty crash damage???
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Where are the actual GM engineers that hang around CF on this mount failure?
And to those that say this failure happens even with the stock shocks **if you bottom them out**. How much travel is allowed with the Pfadts? How much travel does the stock unit have and what are their spring rates at full compression? When maximum compression is achieved, where is that load carried? At full compression does the factory setup send the car flying into the air since the load is split at some % by the K frame and the upper shock mount as well as the lower control arm? If you don't know the answers to these questions you are just speculating as I am.
I'm just sayin'
This is the reason for no warranty. No single person can guess, engineer and or know when and how a car will take a impact, would the shock tower be ok if he only hit a 4 x 4? What could have broken if he hit a 12 x 12 or jumped the car into the ditch???
I will back down now, because I know you will be beating this one failure to death. I have a feeling that we will be hearing about this thread in later years.
Does GM or any other car company warranty crash damage???
Randy
No, you will back down because you know what I'm saying is true and you have no sustainable argument to the contrary. But this isn't about getting anyone to "backdown." It's about clarifying the need for stronger shock mounts and perhaps separate bumpstops (if possible) to make using coilovers safer on the street where it's harder to control what we might run into. And also stronger shock mounts would help to solve the problem of cumulative stress related failures caused by metal fatigue.
And frankly, I don't see any manufacturer offering any kind of guarantee of any kind regarding the safety of coilovers because the shock mounts were not designed to support the weight of the vehicle AND perform their intended purpose. GM designed the car with separate load-bearing springs. Adding the weight of the car to the shock mounts without additional engineering is risky business.
What could have happened if Just J had hit a 4x4 instead of a 6x6 and the shock mount didn't completely fail but suffered a hidden stress fracture which didn't manifest until he took the car out to an HPDE? Not a pretty picture.
And finally I'm not simply referring to "crash damage." I'm talking also about design specs and the fact that the existing shock mounts were NEVER intended to support the weight of the vehicle AND perform their intended purpose. I'm also talking about metal fatigue and cumulative, stress-related related failure of the shock mounts.
I have a feeling we will be seeing more threads like this one as time goes on and people simply slap coilovers on their cars and take them out on the highway.
Last edited by Exterminator; 05-26-2008 at 05:35 PM.
As I said in the OP, it appears that I hit it with the Gurney lip and the little bit of the tire that sticks out from the painted bumper but is still behind the lip. In the words of Maxwell Smart "[Almost] missed it by that much!"
You may want to take a closer look at the mounting clips and facia that hold the lip on. If it didnt flex out of the wayh or rode over the lumber they could have cracked the facia or completely pulled loose. The surrounding mounts can hole the lip in place so it looks fine in cursory inspection, but when you unscrew the bolts you may find something else.
If you hit toward the outside, you are likely fine as the mounts are spaced close enough to distribute the load and flex the lip versus stress and damage the facia. The closer to the middle the impact was, the more likely it will damage the facia as the clip spacing is much farther apart and the facia gives before the lip does.
Location: Location Location NW Suburb Of Chicago, USSA
Quote:
Originally Posted by Erix
You may want to take a closer look at the mounting clips and facia that hold the lip on. If it didnt flex out of the wayh or rode over the lumber they could have cracked the facia or completely pulled loose. The surrounding mounts can hole the lip in place so it looks fine in cursory inspection, but when you unscrew the bolts you may find something else.
If you hit toward the outside, you are likely fine as the mounts are spaced close enough to distribute the load and flex the lip versus stress and damage the facia. The closer to the middle the impact was, the more likely it will damage the facia as the clip spacing is much farther apart and the facia gives before the lip does.
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