Anyone interested in Lab testing a real Fuch?

[dentist90]

I know little about metallurgy, but i do remember that repeatedly bending a ductile alloy will cause work hardening. That's the same principle behind being able to break a wire by bending it back and forth repeatedly. Perhaps the Fuchs that cracked (without hitting a curb) finally reached that point, where instead of bending a crack began to propagate. Age of the wheel and stress history I'm sure will play a significant role.

It would be interesting to find out that an old Fuch was still stronger than a new Japanese cast!

[Jeff Alton]

I agree,

Is an old fuch stronger than a new Japanese/Philipeanese replica?? Who knows, the point of the thread/ question was to find out, and if so, how much stronger?

THere is so much anectdotal heresay on the internet... everything from "failure of a 16x9 fuch is well documented" to "cast fuchs will all fail" to "these are tested to "X" load" that it becomes hard to tell what is real.

Fact is, folks always want to critique based on knowledge and not facts. Ideology and not testing. Nothing wrong with that, I do it too, provided it is taken in context.

cheers

[DARISC]

Originally posted by dentist90
It would be interesting to find out that an old Fuch was still stronger than a new Japanese cast!

Me too. If I was a bettin' man I'd be putting big money on the Fuchs.

[Jeff Alton]

Given odds on that money?

Cheers

[island911]

Originally posted by Jeff Alton
Can you translate that graph into english for us?? ...

Yeah, but you're really pushing my disclaimer.

That graph says a LOT. But the skinny is, forged can take 3x more load, than cast, for any given number of cycles.

fwiw, Rota sez they tested at 100,000 cycles (that's 10⁵) . .about 113 miles of travel. To make that 113,000 miles, we would be looking at 10⁸. This is past the "knee" of the "curve" ... and while there is no endurance limit, it doesnt drop as quickly. And note this is a log scale --10⁹ would be over [Dr Evil] One Million Miles[/Dr Evil].

But of course wheel loads on our cars is fluctuating, and not at max for all those cycles. There are engineering models for this too, but really, that's not needed here. The bottom line is, for a given average stress level, the cast version is not going to last nearly as long as the forged. The difference in life is magnitudes . . many.

[dentist90]

Q: What is more likely to fail at the track, the wheel or the tire?

Aside from not having torqued the lugnuts recently, my greater worry at speed is a tire failure. Are wheel failures that common? My suspicion is that even the weakest wheel will out-endure a tire. But on the other hand, a given wheel may have seen a dozen sets of tires over 30 yrs. Opinions anyone?

[island911]

A tire. BUT, a slow tire leak is not nearly as memorable an event as a fast breaking wheel.

[Wil Ferch]

Too much pseudo science ( or partial-view correct science) floating around in this thread.

IMHO... testing *one* (or a few) old Fuchs and saying you'd get meaningful results that would translate to what other people might see...is not valid. As someone here mentioned, the statistical relevence is lacking unless there is a large test sampling used.

Also... the prior history of the particular used Fuchs comes into play. This was also discussed. How do you translate that to the next user?

Next...the graph indeed shows some information, but people used it incorrectly here on this post. Yes...the forging is stronger and more fatigue resistant ( on the *same* psi basis), but that's the point. Key words..."on the same psi basis". That means....on the basis * IF * the cast component was designed using the forged component's sizing parameters..which usually isn't the case. Meaning?..designers who knowingly design a cast wheel will purposely use thicker load bearing sections than the equivalent forged piece. This is where some of the "fake Fuchs" went off the deep end. The copy-cat Fuch clones in some cases were not made thicker in critical areas to compensate for the cast piece's reduced strength and reduced bending/fatigue resistence. Modern cast wheels that are of different design (than Fuchs) should be designed properly ( made thicker, heavier, unfortunately..in some areas of the wheel) and should be "safe" for any road purpose. However, there are caveats here too. If we don't know the design basis of the new cast wheel...and what regultory agency it was built and designd to comply with ( TUV, etc)...we can only guess on how adequate it is for track purposes.

Nice attempt guys..but this approach to testing an old Fuchs will lead you toward a dead end unless all these other factors are blended into the testing mix.

- Wil

[DARISC]

Looks like Subydude is offering to find out if Rota will do the testing.

[euro911sc]

Originally posted by island911

fwiw, Rota sez they tested at 100,000 cycles (that's 10⁵) . .about 113 miles of travel. To make that 113,000 miles, we would be looking at 10⁸.

I read that as 100k load cycles not revolutions, ie: 100k corners... Testing 113 mi seems ridiculously small for a wheel. that's about enough to see if it rolls straight and thats it. 100k corners is a real test and seems to make more sense. But I have no facts to back up this assumption of mine. Do you know their definition of 'cycle'?

Best regards,

Michael

[Jeff Alton]

A cycle is one rotation. The wheel sees the load constant for the given number of rotations.

Cheers

[DARISC]

There is interesting discussion going on relating to this thread at Performance Products 9x16's