Video: GT350 Crash At The Nurburgring

[sigintel]

Exactly - there was a long thread on this forum about a year ago comparing the stiffness of CF rims with aluminum. CF is stiffest of all of the options - stiff enough that you can actually run less negative camber because the wheels don't bend under lateral G's. Second stiffest is a heavy aluminum rim, like the OEM GT350 rims. The heavier it is the more material there is and the stiffer it is.

The differences between forged and cast is in the yield strength - a forged rim will break at a higher load than a cast rim. Stiffness, the amount a given wheel design bends for a given force, is the same regardless of how the wheel is made. Some wheel designs are inherently stiffer than others, which is why most racing wheels look alike.

Yall are closing in on an incredibly important design factor of wheels!

Grab a box of erasers and start folding them in half and watch them break. Is stress carried on the surface? Do they tear at the outside edges first?

So yield strength is closer to ultimate strength on forged alloy wheels (assuming all forged wheels are same alloy for simplicity of discussion)?

Hmmm, does that mean I can use less material for the same stiffness?

So if I make a forged wheel lighter with less material, how much lighter before its weaker than a properly designed non forged?

Does higher surface stress change how much strain occurs at the extreme surfaces of the spokes vs the center of the spoke? (Think eraser)

Uh, what happens if I decrease the amount of surface yield/strain per stress loading that can occur (ie stiffer elastic)?
How do I concentrate the load at the surface and share less of the load through the center of the material?
What if I want the load to be carried further into the surface of the material?
What impedes the ability of the material in the core/center of the spoke to share loads (especially impact loads)?

What is the difference between shooting an empty beer can vs a full beer can with a 22? Which can supports more weight afterwards?

Hmmm. It looks like I NEED more strain to occur at the surface to get the material deep away from the surface to share more load.
If the yield and ultimate are extremely close together, can I get cracks on the overloaded surface that propogate internally?

Why are pool poles and roll cages made of round hollow tube instead of sharp square solids (like erasers)?

Do you want spokes on your wheel to be sharp square edged? Or smooth rounded closer to a tube surface?
Thin profile? Or thicker?
Total cross section area?

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[Hack]

All aluminum is going to have a tensile and compressive modulus of about 10~11E6 psi. That IS the stiffness. What sets the strength of the material is the alloy.
SNIP
In addition you don't have to use casting factors on wrought products, which means your allowables are in essence higher in that regard as well.

Everything you are saying is correct, but I would say that stiffness is a product of a number of factors. Material is one of them. Geometry is another. You allude to "casting factors". Not sure what you mean, but cast products in general can easily have issues such as porosity or other defects related to the process of casting - all of which impact the stiffness/strength of the final product.

The 'Ring *really* needs to put some soft-barrier on both sides of that corner - nee the white BMW doing a head-on after losing the rear.

Yes I know the track isn't FIA certified but come on, this is just callous disregard for general driver safety NOT to put readily available driver protection devices in place. And how is there not a flagging station that could have immediately flow a waving yellow so successive cars didn't have to panic stop to avoid the stricken white car?

I like how the 'ring is old school. When they say you are taking a risk going on track, they actually mean it. If you want to drive too fast and crash out, you will pay.

 

[TheDeadCow]

When guerrilla marketing turns into a materials lecture...

 

[tyshenry]

Everything you are saying is correct, but I would say that stiffness is a product of a number of factors. Material is one of them. Geometry is another. You allude to "casting factors". Not sure what you mean, but cast products in general can easily have issues such as porosity or other defects related to the process of casting - all of which impact the stiffness/strength of the final product.

Well of course stiffness is a function of geometry. The point was that given equal geometry, a cast wheel and forged wheel will have equivalent stiffness. Just because one wheel is stronger than the other doesn't make it stiffer.

Casting factors are used to account for exactly what you are talking about. But again, porosity won't affect stiffness (assuming were aren't talking about significant voids), but they certainly are crack initiation sites, affecting the strength.

 

[millhouse]

I get the point, and agree to a point. Curious though, how would the wheels you designed have failed? just bent? surely you don't think they'd still be usable after that impact, correct?

Their failure mode from that crash would have likely been a bend or a crack, but the overall integrity would have allowed the vehicle to still roll without completely degrading vehicle dynamics.

So much ignorance in this thread.

So you overdesigned wheels for an OEM? Wow. If a wheel didnt fail after a crash into a wall then that would be considered a fail in my field. And in any performance oriented field for that matter. Its easy as hell to overdesign parts, it's much harder to live on the bleeding edge. Difference between aerospace and OEM automotive I guess.

I used to track SVE wheels and have tracked many other "cheap" wheels. I also design, size, do fatigue and static analysis, FEA work, etc. for a living for a major aerospace company. I work with structure and loading far more complicated than a wheel. All that to say, I have ZERO worry tracking a flow formed wheel.

You show your complete lack of any engineering or manufacturing knowledge with this post. When designing a wheel, my overall goal was to make the wheel not only look pleasant, but to assure the wheel was as light and cheap to manufacture as possible while maintaining manufacturing FEA requirements. I'm not talking about billet wheels here, I'm talking about near net or forged feature wheels as well as near net cast wheels. The less metal we could use, the cheaper our wheels cost and the more profit we could make.

Any aftermarket wheel does not have to meet strict oem requirements. These are over-engineered for a reason. There are actual fatigue requirement numbers as well as safety margins to account for. You can't simply change offsets, rim widths and bolt circles (like all aftermarket companies do). You have to run a full gambit of FEA and adjust spoke widths, depths, radius etc. to account for the changes in bending moments.

Mental note, do not get near any design you have signed off on.

One more note, flow formed wheels only align the grain structure of the rim. The as-cast spokes are still...well, as-cast and much weaker than a truly forged wheel. The biggest benefits flow forming provides is the ability to machine the rim thinner than a comparable as-cast wheel, reducing the rotating mass in the area it counts the most. The other major benefit...while the initial expense of the mandrel is higher, it's cheaper to mandrel turn the rim than it is to fully machine it. Cycle time is quicker as it's mandrel spun and left as-is. There nearly no machining on the rim.

"What is your evidence the OEM wheels are certified tested to a higher standard, the P6G could not also meet that standard, and that JWL-VIA alone is not race track safe?"
Let me start with the later, I never said JWL is not track safe what I did say is I would never track the 6GR wheel or any other cheap alternative. This is what is called an opinion.
Now,VIA is the certification authority and i'd bet that the majority of the 6GR wheels if any don't bare the marking. P6G wheels may or may not meet SAE J175. The burden of proof is on them not me, I am the consumer. However, it seems they do not as they do not list it as a testing standard but proudly list the JWL VIA and JAWA https://project6gr.com/wheel-safety/ .
See millhouse's post above regarding OEM wheels, he seems to to the an SME.
We have established that the SAE J175 is a more stringent standard than JWL, "Doesn't mean that a wheel with JWL VIA certified wheel is better or worse than a wheel that claims to meet any other high standard" Also, millhouse's statement corroborates my position. Sorry milllhouse, didnt mean to drag you into this.
Finally, Ford Performance wheels use SAE J175 as a minimum test standard https://performanceparts.ford.com/performance-wheels/

In summary, only if the wheel meets or exceeds OEM standards or has other certifications and race cred like the Signature wheels and Forgelines for example, would I use the wheel for the track. This is my personal opinion and no one else's lol

This crash was caused by lack of skill.

Indeed. The crash was in no way caused by the wheels, and any OEM wheel likely would have been damaged.

With that said, unless the aftermarket companies have the exact force requirements for FEA (which would require forces encountered from suspension components, braking, multiple impacts etc.), they are most likely just running standard loads and will not meet anything close to a manufacturer unless completely over engineered (which nearly all of them aren't). Again, the biggest giveaway that companies aren't running unique FEA on these wheels based on Fords requirements can be seen when the exact same spoke width and varying bolt circles and wheel width are available for the same design. Varying these parameters nearly always necessitates a redesign of some sort. Never does any aftermarket company specify the vehicle that the wheels were designed for. The same wheels could fit on a variety of vehicles which would obviously have drastically different requirements.

One more thing people need to keep in mind. When talking about SAE or JWL testing, those are physical testing requirements, not design requirements. Just because a wheel passes SAE or JWL testing does not mean it is safe to use for a vehicle. These tests are wheel rating loads, not vehicle ratings. It assures the wheels are safe to use on US, European or Japanese roads but does not mean the wheel will be safe to use on a track or will hold up to a pothole on an F350.

 

[millhouse]

Don't aftermarket car parts in Germany require TUV approval, which is much stricter than US standards?

Yes. Not necessarily stricter, but parts are designed for specific vehicles. Aftermarket wheels in the US are not normally designed, engineered or tested this way..hence the reason for my posts.

 

[tyshenry]

You show your complete lack of any engineering or manufacturing knowledge with this post. When designing a wheel, my overall goal was to make the wheel not only look pleasant, but to assure the wheel was as light and cheap to manufacture as possible while maintaining manufacturing FEA requirements. I'm not talking about billet wheels here, I'm talking about near net or forged feature wheels as well as near net cast wheels. The less metal we could use, the cheaper our wheels cost and the more profit we could make.

Any aftermarket wheel does not have to meet strict oem requirements. These are over-engineered for a reason. There are actual fatigue requirement numbers as well as safety margins to account for. You can't simply change offsets, rim widths and bolt circles (like all aftermarket companies do). You have to run a full gambit of FEA and adjust spoke widths, depths, radius etc. to account for the changes in bending moments.

Mental note, do not get near any design you have signed off on.

One more note, flow formed wheels only align the grain structure of the rim. The as-cast spokes are still...well, as-cast and much weaker than a truly forged wheel. The biggest benefits flow forming provides is the ability to machine the rim thinner than a comparable as-cast wheel, reducing the rotating mass in the area it counts the most. The other major benefit...while the initial expense of the mandrel is higher, it's cheaper to mandrel turn the rim than it is to fully machine it. Cycle time is quicker as it's mandrel spun and left as-is. There nearly no machining on the rim.

You quite literally refuted nothing I said. So you over designed wheels?

And you're right, I have no clue about engineering or requirements. I am sure your wheel FE models were incredibly complex.

 

[millhouse]

You quite literally refuted nothing I said. So you over designed wheels?

And you're right, I have no clue about engineering or requirements. I am sure your wheel FE models were incredibly complex.

Do you understand manufacturing load requirements and margin of safety?

The wheels were adequately designed for both.

And I've worked in aerospace. We still had load requirements, redundancy requirements and margin of safety requirements.

Do you not understand the wheel you "have zero problem tracking" isn't safe simply because it's flow formed, and likely will fail at much, much lower loads than nearly any OEM offering?

Honestly, if you have any semblance of FEA and engineering knowledge, it should bother you very much that the wheels you are defending likely have not been analyzed for your mustang, let alone for the dynamic systems involved with a magneride suspension.

 

[tyshenry]

Do you understand manufacturing load requirements and margin of safety?

The wheels were adequately designed for both.

And I've worked in aerospace. We still had load requirements, redundancy requirements and margin of safety requirements.

Do you not understand the wheel you "have zero problem tracking" isn't safe simply because it's flow formed, and likely will fail at much, much lower loads than nearly any OEM offering?

Honestly, if you have any semblance of FEA and engineering knowledge, it should bother you very much that the wheels you are defending likely have not been analyzed for your mustang, let alone for the dynamic systems involved with a magneride suspension.

Yes I understand load requirements and margin of safety. I work with these concepts every day. And just because a wheel is designed to a specified load requirement doesn't mean it ISN'T over designed. You already mentioned factors of safety. I assume you know why these exist right? You also understand they are somewhat arbitrary right?

You aren't telling me anything I don't already know.

I think it is hilarious that you think an independent company wouldn't be able to come up with reasonably accurate loading for a given car. As if the FBD for a wheel attached to a hub is some black magic voodoo. As if you can't take masses, accelerations and determine reasonable loads. As if a company making wheels couldn't POSSIBLY make any of that happen. I promise you I could.

You do know there are 100's of thousands (conservative estimate) of examples out there of people successfully tracking aftermarket wheels right?

Curious, do you even track your car?

 

[millhouse]

Yes I understand load requirements and margin of safety. I work with these concepts every day. And just because a wheel is designed to a specified load requirement doesn't mean it ISN'T over designed. You already mentioned factors of safety. I assume you know why these exist right? You also understand they are somewhat arbitrary right?

You aren't telling me anything I don't already know.

I think it is hilarious that you think an independent company wouldn't be able to come up with reasonably accurate loading for a given car. As if the FBD for a wheel attached to a hub is some black magic voodoo. As if you can't take masses, accelerations and determine reasonable loads. As if a company making wheels couldn't POSSIBLY make any of that happen. I promise you I could.

You do know there are 100's of thousands (conservative estimate) of examples out there of people successfully tracking aftermarket wheels right?

Curious, do you even track your car?

In bold is your biggest issue. These companies aren't coming up with specific loading's for the mustang. They are applying standard spec loads for their designs and offer them in many configurations. They aren't designing mustang wheels, they are designing wheels that fit mustangs. Again, I'm not sure how you don't recognize the difference given your apparent title.

Nope, never track my car. I have however had to COMPLETELY redesign wheels based off a simple 10mm offset change by an OEM. But yeah, it's OK for aftermarket companies to offer the exact same wheel geometry with different offsets and is completely safe for track duty in any configuration.

Also, you do realize I never said aftermarket wheels weren't safe to track don't you?

Edit: On a side note, any engineer that doesn't design a product with an adequate margin of safety (if you want to call that over-designed, so be it) where human life is a concern, then they are breaking the very first cannon of the engineering code of ethics. Wheels happen to be one of those areas that have the ability to induce catastrophic vehicle failure and are absolutely over engineered by all OEMs and tier suppliers. Any parts designed "on the bleeding edge" have no business being around a human.

 

[Billy1]

OK guys enough with the wheel's metallurgy master's dissertation. This was driver error. A 3800 lb vehicle in motion will always destroy a wheel if the wheel has to absorb all that energy. Now if the wheel had been made of trillium the accident would never have happened lol. Just kidding, Trillium is heavy metal but not the one for wheels.

As for barriers on the Nurb,, figure out much 1 lap would cost if they had to upgrade all the "favorite" fences. A lap would go up from 20 Euros to probably a 100 to cover costs..

 

[Hack]

But again, porosity won't affect stiffness (assuming were aren't talking about significant voids),

What's the stiffness of air?

On the bright side, porosity definitely reduces wheel weight.

 

[millhouse]

metallurgy master's dissertation. This was driver error. A 3800 lb vehicle in motion will alw

What's the stiffness of air?

On the bright side, porosity definitely reduces wheel weight.

Back in the day, OEMs were playing with loss foam casting pockets in the center of spokes. Not that were talking about the same phenomenon, but interesting none the less. An example here.... http://dirtyoldcars.com/porsche-hollow-spoke-wheel-technology/

For us, it was it bit too expensive and unproven at the time.

Another interesting note. We continually designed EXTREME light weight wheels for OEM's high performance cars. None really took, as they were always the same simple design (thick spoke section, extremely thin with large corner radius).

Here is one of my favorite designs (Near net forged, 5 axis machined, spun rim). As you can see, weight was definitely a priority on this. The back side of the hubs have extra machining to hog out as much weight as possible.

 

[Hack]

Back in the day, OEMs were playing with loss foam casting pockets in the center of spokes. Not that were talking about the same phenomenon, but interesting none the less. An example here.... http://dirtyoldcars.com/porsche-hollow-spoke-wheel-technology/

For us, it was it bit too expensive and unproven at the time.

Another interesting note. We continually designed EXTREME light weight wheels for OEM's high performance cars. None really took, as they were always the same simple design (thick spoke section, extremely thin with large corner radius).

Here is one of my favorite designs (Near net forged, 5 axis machined, spun rim). As you can see, weight was definitely a priority on this. The back side of the hubs have extra machining to hog out as much weight as possible.

Love the wheel design. Definitely hollow structures can have huge advantages over solid if they can be produced reliably and repeatably.

 

[nastang87xx]

All this about engineering principles and this and that and there is still simply a fundamental thing that no one else has mentioned but your resident MAGNAAAAAAAARIDE call-out asshole:

THERE ARE VARYING DEGREES OF QUALITY REGARDLESS OF CONSTRUCTION METHOD. You can forge a wheel but if you have done a shitty job you're going to get a shitty product. You can flow form a wheel and if you're particular and you go through smart manufacturing processes and quality control, you will have a good product.

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