Fuchs are mostly Magnesium

[blue72s]

Is a pitted Fuchs rim dangerous? Can pits be sanded out prior to anodising? Are most Fuchs pitted by now?

[nick-moss]

Most of the deep 6" rims that I am refurbishing have some kind of pitting, but it only becomes obvious when the paint and anodising is stripped off. The upstand of the rim can be lightly turned to remove the pitting, then polished before anodising again.

Designations for Aluminium Alloys:
Major Alloying Element / designation

None (99%+ Aluminium) / 1XXX

Copper / 2XXX

Manganese / 3XXX

Silicon / 4XXX

Magnesium / 5XXX

Magnesium + Silicon / 6XXX

[surflvr911sc]

All metal will corrode over time. How the surface is treated and the conditions that the metal is exposed to will determine the rate of corrosion. The anodizing is probably the best protection for the many different conditions that our wheels are exposed to. Powder coating & painting would be next. A polished surface is the most vulnerable but the polishing itself provides protection, if it’s kept up.

Pitting will happen and is not dangerous it self, but left unchecked the metal will continue to corrode and the wheel will slowly loose integrity until it cracks. Slight pitting can be sanded and polished out but unless you take enough material off to get every bit it will continue.

The best defense for a non-coated polished wheel is to polish them often.

I have an extra set of 16x9's in the garage. How about I build a fire in the back yard throw them in and see if they burn?

[thabaer]

Originally posted by surflvr911sc
A polished surface is the most vulnerable but the polishing itself provides protection, if it’s kept up....The best defense for a non-coated polished wheel is to polish them often.

Not quite right, the natural aluminum oxide that forms rapidly does an OK job of protecting the alloy. Frequent polishing removes the relatively tough oxide layer (that's the black stuff you get on the polishing rag) and re-exposes a new layer of aluminum to oxidation.

Frequent WAXING is what you want.

[surflvr911sc]

Hmm, I agree that waxing in between is an excellent way to protect them, very good point. I can’t say that I completely agree w/ an oxidized surface being better than a polished one though. Disclaimer- I’m not a metallurgist.

An oxidized surface is pitted. This not only has corrosion already in progress but also allows more surface area for the oxidation to occur. A well polished surface has much less surface area for the oxidation process and removes much of the existing oxidation.

What do think?

[Wil Ferch]

The true reason of the lightweight nature of the Fuchs are because they are forged ( "squeezed") and you don't need the thickness of the weaker casting process to get the same strength...

BTW....they (Fuchs) are predominantly "aluminum".....even Pano had an article comparing the relative weights of a 911 steel wheel, a 911 Fuchs "alloy" wheel , and a much larger 917 Magnesium wheel which was..at the same time... much, much lighter.

-- Wil Ferch

[KTL]

Not to get off topic here, but I remember when reading about polishing, it was said that some wax (like carnauba for instance) is not recommended for polished finishes. The wax is acidic and porous.

Here's where I read the above:

http://englishcustompolish.com/usca/myths8.html

[nick-moss]

From that web address above

Metal Polishing Myths, Half Truths and Lies
21. All metals can be polished

Not to make them shine they can't.

There are some people out there that say they have a mag and aluminum polish. Well magnesium doesn't shine. Not bright anyway. It's a white metal. You can clean it. You can remove oxidization, But you can't polish it! In mag alloys it depends on the amount of magnesium content as to how well it shines.

[RickM]

Quote: "I can’t say that I completely agree w/ an oxidized surface being better than a polished one though. Disclaimer- I’m not a metallurgist."

For the record: Anodizing is a controlled form of natural aluminum oxidation. I learned this while reading up on the development of and the mechanics behind casting aluminum.

[banjomike]

Paul Frere refers to some cast Al wheels with a high Si content introduced in '73. I don't belive I have ever seen these. What do they look like? Are they the 914 wheels?

[911ctS]

I too have no creditable sources to back me up....but has anyone ever compared the weight of an origional Mini-Lite wheel to a Fuch wheel. It seems as though their compositions may be very similar, judging by their appearance when polished. However in my opinion the Fuchs might have a bit more Mg because of their texture and slightly porous make-up. Just throwing in an idea.
Clint

[thabaer]

First, I prefer black center Fuchs with the standard clear coated lips, you guyz poliching yer Fuchs are all knuts

Yes, a smoother (polished) surface should present a more difficult environment for little nasties to eat at the alloy, and trying to give preference to doing a protective coat vs. re-polishing is only keeping you from knocking off a few molecule thick layer of oxide.

As cleaners, the P21S stuff that the Porsche-Audi dealers (and Eagle One? ) sell is a good non-acid cleaner/polisher. Hitting them with a good protectant coating (what I meant by wahxon/wahxoff) after the polish helps the polish last and keeps them a bit cleaner than just the raw polished surface will.

...and of course, dirt is unsprung weight!

[RickM]

Also, many of the polishes contain oils which are left behind for protection.

I purchashed "Wheel Wax" for painted wheels. Seems to work well. I think it merely is more tolerant to heat and to being easily washed off. Not sure how it would work on polioshed aluminum.

[banjomike]

I am a Mechanical Engineer, and I had a class in metalurgy.

Each time you polish a surface, you remove a bit of the surface. With a paint you can eventually polish right through to the primer. This is not likely to be an issue with these wheels. Polishing regularly will likely prevent pitting and the stress risers and cracking associated with pitting.
Bare polished aluminum (and magnesium, and lead, and others) will oxidize rather quickly.
Aluminum is a great weather resistant metal becuase of this naturally occuring protective layer.
The natural oxidation is not as robust as an annodized layer.
Annodizing is hard and scratch resistant, bare aluminum is soft and scratches easily.
Fuchs wheels look good even when annodized or oxidized.
Polished Fuchs look Great.
My Fuchs need cleaning.

MsB

[andyjboy]

banjomike wrote:
Paul Frere refers to some cast Al wheels with a high Si content introduced in '73. I don't belive I have ever seen these. What do they look like?

These would be the Cookie Cutters - introduced as the standard fitment for 911E's in 1973.

As for the composition of forged Fuchs wheels I believe that the the main metal is aluminium with a low (if any) percentage of magnesium. From the Fuchs website (under 'history') :

..."We are the first company in Europe to manufacture forged aluminium parts, synchronising rings and forged aluminium wheels for mass-produced passenger cars"

Andy
'69 911E------>R

[blue72s]

Were early (pre-71) Fuchs fully anodized inside and out, or just on the face?

[dvkk]

The Bentley manual I saw that states "forged magnesium" was the 78-83 911SC manual. I can't quote the page because its a manual my friend has. I'll look later today.

I'm still waiting for someone to come up with another explanation as to what the AS10.62 means. George's pic clearly shows this Mg alloy designation. If it were aluminum it would be a 4 digit number conforming to the standard Nick posted above.

What is the alloy designiation on the side of a 77 or earlier engine case? Is there any?

If you look at the Mg engine case on any 70s VW Beetle, down on the side of the sump it will say either AS41, or AS21.

[Randy Webb]

I may be the source of dvkk's original post here, as I noted in the other thd he mentions that a Chistophorus article stated that the Fuchs were forged aluminum to correct a post he had stating they were Mg.

Now, altho that is a PAG rag, and should be correct, I don't really know what they are made of. They resmeble Al, are as strong as one would expect forged Al to be, are heavier than the Mahles, and etc. I don't know anything about the code stamped on the side or why it would mean what he says it means.

I propose we grind one up and run it thru a mass spec. That will be proof of the pudding -- more os than any claim stamped on the side.

[Wayne 962]

Hmm, I thought someone would have been able to come up with a definitive answer by now...

-Wayne