http://forums.pelicanparts.com/uploa...1100614591.jpg
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Craig, I was just made aware of this thread and read through it rather quickly (forgive me if I’ve missed anything) but, I wanted to jump in as quickly as possible. I’m Very sorry to see this happen and very thankful that the damage to both you and your car were minimal. I am always VERY concerned when there is a failure of any kind with our products

There are some very good observations in input on this thread and I’d like to add some to it from my side

The Original kit designed does call for the nut to be on the bottom. If the bolt is to break the first place suspect is always going to be the threaded area. With that said, in my opinion there is no doubt that the break was caused from being under torqued rather than over torqued. While it is agreed that double shear is always the preferred method there was a lot considered in the design of this kit. Assuming the bolt was originally torqued correctly and with the length spacer on you kit (1.500”), the lateral g loads from a 10.5” Goodyear slick were input to FEA which gave use the results that the Grade 8 bolt provided will handle many more times the shear load in it’s geometrical position than the tire can produce. However, it is quite evident that a failure did occur and I’m very concerned and want to learn exactly why.

Here are my first concerns:

1) HAD THE BOLT EVER BEEN REMOVED AND RETORQUED AT ANY POINT TO YOUR KNOWLEDGE? If so this “could” have caused the bolt to stretch causing the start of premature fatigue. As always, keep in mind that these are racing parts and they require more attention than conventional street car parts. The bolts should always be replaced after being removed and inspected. (I say this partially to remind others that may read this thread)

2) ARE YOUR SPINDLES AT STOCK HEIGHT? If they are then the bumpsteer kit used in this case is likely too long which would cause the bearing to run out of it’s articulation range. If this is the cause it could be binding which will cause the loads to go to infinity which in turn would cause overstressing of the bolt for sure. If this is the case you’ll see evidence of this on the rod end.

Please call me at your earliest convenience at 562-595-5575.

Cary Eisenlohr/ERP

It had been removed - once about a year ago to install the raised spindle RSR struts.

Won't the shank of the bolt be necessarily be larger than the o.d. of the threaded portion, and thus have a tighter fit in the tapered shim that takes up the space in the taper of the control arm -- being superior in resistance to rocking motion?

IE shouldn't the bolt be installed head up?

I'll give you a call,

Craig,

Thanks for the compliment -- no genius here, just a car geek and engineer who loves to figure out how things work and especially why they don't when something goes wrong.

To your most recent question, the OD, or major diameter of the threaded portion of the bolt, should be the same as the diameter of the shank, or unthreaded portion. I believe that the orientation of the bolt (head up or down), wouldn't make very much if any difference to the outcome in this case. This is because the same bending load would have been applied in several places along the bolt, both near the top and bottom, if the system loses tension. Because the threads represent the "weakest" part of the bolt, failure would be expected to occur wherever the threaded portion (thus smallest cross-sectional area and highest stress) is located.

Bigrubberjeep,

I have to second your appreciation of that photo. I like it too. That's Randy (from Seattle) in his modded 930. His car is very well prepped and he's a great driver and nice guy. From reports, his lap times, on Hoosiers or Kumhos are within a second or so of race laps from the GT3 Cup car I crew for on occasion. So who needs a Cup Car when an old 930 will do?

Cary,

I'm glad to see you're aware of this and have responded. I've personally owned an entire ERP suspension on a previous car and had the pleasure of admiring the jewel-like quality of your components. I currently have your bump steer kit on my 930, hence my higher-than-normal level of interest in this thread. I do hope you'll give us your wisdom on what, if anything, you'd recommend to lessen the chances of this happening in the future.

Cary - I called 3x no answer and your system doesn't accept voice mail msgs

P.S> Hey thanks I took that badass pic above ;-)

Craig sorry I wasn't in this morning and the mailbox was backed up ... If you can send me the parts I can take a closer and replace it. If you were running with stock struts before it most likely went into bind and thats could have started it all. At any point I still feel if everything is working freely (not in bind) the parts are strong enough. Do you know the height the stuts have been raised?

I too have this Bump Steer Kit installed
 

And I have stock struts. The car is lowered significantly however, and the geometry looks fine at rest.

Is is an absolute requirement that the struts have raised spindles to use this part?

Chris

Cary -

All I have are the 2 bolt halves, the nut, and the 1/2" sleeve.
All the other pieces are somewhere amongst the 1/8 mile debris field ;-)

Craig, send me what you have including the the rod ends. The rod ends will tell me if you were in bind. Email me as carnutt@aol.com

Re: I too have this Bump Steer Kit installed
 

Chris,

The 1.500" space was made of a care with spindle lifted about 20mm above stock. If you are using them with stock height spindles I would run a 2 to 3 inch bump curve ... you may find that you are getting tow out in the bump direction. A quick check is to see if the tie rod arms are roughly the same angle as the lower A-arm. Many people think you want the tie rod arm parallel to the ground ... that would only be true if your a-arms are parallel too. Bump steering a car to zero is getting the arch of the tie rod to match that of the A-arm in the operating motion. The best you will ever get will be between 2.00" to 2.50" of travel

Just to add my $.02 on this thread.

Craig,
Glad the stars were in alignment that day.

Somewhere in one of Carroll Smith's books, he advises against using any SAE-graded fastener in a critical part of a vehicle. First of all, they're not strong enough. I would consider the suspension one of those areas. In addition, the fastener manufacturer may be unknown; the material, heat treatment and strength may not be to spec and thus may be compromised. I recall Smith calls these "moonglow" products. They might have a place on a street hot rod but not on the track.

Not sure about the geometry issues, but it appears ERP is on the case and will get this resolved. I would dump the SAE graded hardware ASAP and replace with higher strength AN or NAS-graded threaded fasteners (and equivalent nut) with the appropriate grip and thread length.

Sherwood
PS: I didn't like the upside down position either. Good catch Chuck.

Cary,

I will measure the angles at rest and let you know the results.

Thanks for the details.

Cheers,

Chris

While I feel this bolt failure is an isolated incident, it raises extreme concern with me and I plan to take every measure to understand every scenario that could have cased the failure. At the same time we have over a 1000 kits out there and I’m also concerned that we don’t start unnecessary panic if there isn’t a particular problem. There are some very very good comments on this thread. In fact I have a good feeling one or two of the people commenting (Rob for one) have more than "a little” experience with metal fatigue :) . With that said, I want to make sure that there aren’t any misunderstandings about Grade 8 bolts and especially what Carroll has written or said since he was one of the people that has made me feel comfortable about using Grade 8 bolts in the first place.

The fact that Carroll Shelby uses SAE Grade 8 as the standard to compare all other bolts should mean something. To quote his book in Chapter 4 he says:

“There is more misinformation in circulation about nuts and bolts ---particularly bolts--- than all of the other parts of the racing car combined. Claims and counter claims of ‘equal to SAE grade 8’ and ‘superior to grade 8’ stare smoothly from the printed page to seduce the unwary”

Further he says “There are at least three corporations presently hyping their version of superior to SAE Grade 8 bolts. They are junk. They have always been junk and, presumably, they will always be junk. He then says, “If the SAE felt ANY need for a series of bolt specifications to be superior to their Grade 8, they would come out with it.”

I’d also like to clear the question of “moonglow” I was able to find the quote and it said: “The super-whatever claims are pure moonglow --- a sales gimmick designed to rape the innocent, the unwary and the ignorant.” The moonglow was referring to the ‘superior to Grade 8 bolts’ NOT the Grade 8 bolts. The biggest problem Carroll has with Grade 8 is that if he wants a longer shank or safety wire holes he would rather buy an AN or NAS already built that way rather than cutting and drilling the Grade 8. But I don’t know of any quotes where Carroll claims that the SAE Grade 8 is a clearly inferior bolt.

As far as counterfeit bolts being out there, he talks about there being as many, if not more metric or aerospace bolts.

note: These are quotes from Carrolls book so, if the above sounds aggressive ... it's not me ... it's him! :D

While Smith touts the virtues of SAE 8 fasteners from reputable manufacturers, he also admits there is wide counterfeiting in the industry. Furthermore, Smith says (also in Chapter 4),

"The specifications to which they (ed. SAE 8) are manufactured are excellent. The enforcement of the specs is not, however, so can never quite be sure of what you are getting. Further, SAE bolts are designed for tension applications and their shanks are a few thousandths undersize for shear applications."

"Once you have paid for the SAE bolt, your work begins. First, you will probably have to saw off a bunch of threads. Next, you get to finish the sawed off end. Finally, you may drill a safety wire hole in the head. The FAA does not allow the use of SAE-graded bolts on aircraft and that should be some sort of clue."

Thus his preference for AN, MS or NAS graded fasteners.

Here is a fastener chart from his book with comments:
http://forums.pelicanparts.com/uploa...1100769078.jpg

Hope this helps,
Sherwood

Ok; here's a marketing guy weighing in (although I have read CS's book and keep them as references). Here are my two thoughts.

1) I think that the bolt being installed upside down may be a key contributor.

2) In this case using an SAE rather then NAS bolt also was a key contributor, more because of the bolt's design then the metalurgy.

Bolt being installed upside down:
Using the picture below I think that I can visuallize how the original designer of this set-up intended it to work. On the face of it it appears to be a reasonable concept to me.


http://forums.pelicanparts.com/uploa...1100783554.jpg

a) With the bolt properly installed and torqued, the overwhelming force on it should be in shear (Black line).
b) When the bolt is properly torqued, any bending forces should be carried by the conical sleeve (red arrows). Since the tie rod is not flexible, there should be relatively little bending force at the top of the assembly above the steering rod.
c) Most of the bending forces should be handled by the rod-end at the bottom (orange arrows). Note that the bolt runs through a sleeve through the center ball of the rod end, so there shouldn't be any bending forces on the bolt in that area.

Now with an SAE bolt installed upside down a few things happened.

1) What bending forces the bolt did see are are focused at the top of the assembly. If the bolt were correctly installed, this would be part of the shank of the bolt and not threaded which makes it quite strong. Instead, with the bolt installed upside down these forces were focused on the treaded portion of the bolt which is the weakest area.

2) NAS bolts have a longer shank and fewer threads at the top. Using an SAE bolt here resulted in the threads extending down through the steering rod. If the proper NAS bolt had been used, where the threads did not continue down below the bottom plane of the nut, once again there wouldn't have been threads in the stressed area -- even if the bolt had been installed upside down.

My conclusions:
1) The bolt orientation is critical.
2) Given the very critical application of this bolt, here I would think it is worth the money to invest in an NAS bolt for the highest level of security and safety.

Good points, all.

** I think we really need to hear Cary weigh in on the bolt orientation issue **

We have:
Right side up is better
Upside down is better
Either way it does not matter

Cary - What is your take on this?

When I send in the parts to you, receive parts back.....how do I/we install the bolt?

This kit was designed to have the bolt go through the top of the steering arm with the treads pointing towards the ground and the nut on the bottom.

I still need to see the rod end to see if there are any signs of binding. If the picture of the good side is in full droop you can see the ball starting it’s articulation going upward which will only increase as the car goes down to rest and then into bump were it may be to the point of bind. If this is indeed happening it will cause ANY bolt break at that point.

Again, this is very serious issue and our choice of using Grade 8 bolts did not come without lots of thought. The point I was trying to make in my earlier response about SAE Grade 8 bolts was not made to correct or argue with any one, rather to point out that SAE grade 8 bolts are the standard of which other bolts are measured and they are far from considered junk. The reason they are not used in aerospace is because they don’t have custom lengths or certification which drastically increases price and doesn’t guarantee them to have higher yields. The fact still remains they are the best quality bolt readily available to all of us which is important when rebuilding and replacing used bolts during regular maintenance.

How many people know where to buy new certified NAS bolts? And if you do, are they the bolts you need in stock? Are they willing to order and sell you just two at a time? On occasion I’m asked to do seminars on suspension tuning and when I ask this exact question the most common response is the name of the nearest surplus store (weather they realize it or not) not a certified reseller that offers them brand new with certs. One point that can’t be emphasized enough, NEVER purchase NAS bolts from a surplus store. This is where millions of dollars worth aerospace scraps ends up and it highly likely many are counterfeit.

Another example of the complexity getting bolts is this; I’m holding two NAS bolts in my hand right now that are visually identical in every way. If you look very closely on the heads, one is stamped NAS 6305-17 and the other NAS 6805-17. How many people that will read this thread can tell me which will yield sooner and will that one yield sooner than the same size Grade 8? NAS bolts introduce more critical variables which can also add risks.

I know a race team first hand that “upgraded” the bolts in their brake rotor hats to NAS and didn’t understand how to read the numbers. BUT, they had just read an article on how NAS bolts were superior to SAE Grade 8. The bolts they got were the most expensive of the NAS bolts they had to choose from. They found out the hard way that those more expensive bolts were in fact more special then they had bargained for. They were extremely strong but couldn’t exceed a specific temperature. They went out in one session with no indication of any problems … the next session EVERY SINGLE BOLT attaching the rotor to the right side hat sheared causing a pretty ugly crash. Point being if you thoroughly understand aerospace bolts there can be advantages; however, I still don’t think it’s the best answer for the majority users.

I 'borrowed' a new section of the kit - the vertical assy - to get the car up & running again. Perhaps I can take details pics of the area you mention - I believe I know what you are looking for.

We can go from there & see if it shows anything, otherwise I'll send the tie rod end to you also (I don't have one here to install to get the 911 up & running)

I'd like to chime in on this and suggest that it might be appropriate to refrain from making statements about the suitability or applicability of the bolt, it's grade, or hardware in question without having firsthand knowledge of the development process or analysis that was undertaken. It's one thing to read a book and transfer some concepts to a situation like this, and quite another to have actually undertaken the engineering to bring a proven product to market. Opinions without professional credentials add little to the discussion, and potentially have the unfortunate consequence of causing a negative perception without basis. Let's give the people directly involved some time to figure out what happened without a bunch of speculation.

One thing that can be gleaned from this thread is that it's very important to put your hands (personally) on your car and check everything at regular intervals when it's used for track purposes.