Fuchs are mostly Magnesium

[dvkk]

There was a question in another thread about the actual alloy of Fuchs that didn't really relate to that other thread, so here is what I have.

Fuchs are predominantly Magnesium

The alloy is indicated just under the part number on the back of the spoke. Refer to this pic:

http://forums.pelicanparts.com/uploads2/realfuchsagc1070783562.jpg

in this thread:

replica fuch wheels?

On this 7x15, the alloy is AS1.62, which is a designation for a Mg alloy. The A stands for Aluminum, the S for Silicon. The numbers following are the alloying %. In this case, its 1% Al, 6.2%Si. It could also be 10% Al, I'm not quite sure since on late 6x15s they list the alloy as AS10.62. I tend to believe the latter since wheels with 95+% Mg tarnish so much faster than Fuchs. There may also be near insignificant amounts of Mn, Zn, and Ni. What AS numbers are cast into 77 and older engine cases?

Ever wonder why a Fuchs polishes up so much nicer than any aluminum wheel ever made? It isn't because its forged, there are plenty of forged aluminum wheels out there that look bland when polished compared to a polished Fuchs. The reason a Fuchs polishes up so much nicer is because of the Mg.

One huge problem with a Mg wheel is corrosion. This is why Porsche specified the wheels to be anodized. How many other wheels do you know of that are anodized? Fuchs had to be anodized to protect the Mg.

Notice how light Fuchs are compared to other aluminum wheels of the same size? Again, its due to the Mg, which has a density of 63% of that of Al. Fake Fuchs always weigh around 50% more than the real thing, partly because they are all cast, and partly because they are all made from higher density aluminum.

When Al Reed gets an Alum Porsche wheel that needs welding, he farms it out to a shop just down the street. Any Fuchs that need welding goes to a different welder, since that shop down the street doesn't weld Mg.

Does anyone have the Bentley manual handy that can look up the info on Fuchs in a section called "Road Wheels"? The one for SCs should do. What does it describe them as?

[GeorgeK]

While there IS Mg in a Fuchs, I doubt they are mainly MG.
I have wheels that are mainly MG (951 Cup phone dials), and the alloy is very different, much softer to the sandpaper.
My wheel repair guy (a master tech at welding) uses aluminum to weld them. A specific alloy rod if I want to anodise them, but by no means a MG predominant alloy.

[Adam]

Cool write-up. That's my photo you've linked to and I was wondering what all the other numbers meant. I was assuming that they were batch identifiers or something.

[Wayne 962]

Is this opinion or fact? You don't site any references. While I am not a wheel expert, I have always felt that the Fuchs alloys were a standard alloy of aluminum, not predominently magnesium. I have a set of the Mahle gas burners - they are definitely lighter, and they also have different finish patterns.

Your comment on polishing Fuchs also doesn't necessarily jive with me, because as most people here know, magnesium doesn't polish well (try polishing your mag fan blades). The Mahle gas burner wheels are painted - never polished, because the magnesium corrodes and tarnishes so easily.

Fuchs are very strong - they are known for that. The Mahle gas burners are known for being pretty weak due to their magnesium construction.

A useful table put together by Sherwood can be found here:
http://members.rennlist.org/911pcars/WheelWts.html

"Notice how light Fuchs are compared to other aluminum wheels of the same size?"

The 7x16 Phone Dials are only 1/2 pound heavier than the forged Fuchs?

A Google search on "AS 1.62 magnesium" resulted in no matches.

This is quoted from www.gasburner.net/wheel.htm:

"Because of the high amount of magnesium in these wheels the unprotected polished part turn into a light grey surface within a week or two. To keep the wheels to a high standard requires a good polish once a week."

I'm open to learning new information, but you don't site any sources to back up your claims here.

-Wayne

[dvkk]

Mahle Gas Burners are lighter because they have much more Mg than Fuchs, and weaker because they are cast, not forged.
Freshly polished Mg wheels and fan blades look so much more brilliant than any aluminum wheel, because of the Mg. Pure Al does not polish as well.

I agree that table by Sherwood is useful, but the weights are not. How can an 8x16 Fuchs be 2lbs less than a 7x16? The 8x16 Fuchs are 16lbs, and the same size Phone dial is a hefty 20lbs. That's 25% more.

Look in your Bentley manual. I already know what it says. It calls Fuchs "forged magnesium". Isn't Bentley endorsed by Porsche?

Check out this link:

http://members.tripod.com/Mg/mggen.htm#alloys

Scroll down to table 1. Note the alloy designated AS41. The AS #s are the alloy. You may not find this alloy listed if it were a specialist alloy Fuchs made up for the unique manufacturing process to make the wheels.

[Cornpanzer]

With no facts to back it up, I must agree that i have always thought that Fuchs do have a tangible amount of mag in them. They do polish very nicely and have a coloration to them when polished that only comes from mag. However, I dont see how it could possibly be predominant. We have seen way too many unanodized fuchs that last years without being repolished. My mag Americans last about two weeks in the dry weather before they turn. Thats what a predominantly magnesium wheel does. You cant even touch a true mag wheel because the oils in your skin will leave a blotch on the finish.

[GeorgeK]

Sorry, but you need to give us some background. Do you have a special interest, or knowledge we don't have, we pelicans, or the people who repair these wheels and say they are predominantly aluminum?
If you are a metallurgist, then all you say is welcome, otherwise, please give us some clear info.
I for one believe, based on my hobby with them and their restoration, that they are forged aluminum, with a small part of other components, like Mn, Mg, Si, and others.
Not picking a fight, but I like objective info.

[Wayne 962]

Originally posted by dvkk
Look in your Bentley manual. I already know what it says. It calls Fuchs "forged magnesium". Isn't Bentley endorsed by Porsche?

Uhh, your credibility is *rapidly* disappearing. First of all, Bentley has nothing to do with Porsche - the factory won't even license any diagrams for Bentley to use - they have to recreate their own (like I have to). Secondly, the Bentley manual (while good) has so many errors it is almost embarrassing. I think that they fixed a lot of the mistakes in this 2nd printing, but the first edition could be described sometimes as 'dangerous.'

That said, the Bentley manual does not say "Forged Magnesium" as you claim. On page 440-3 of the Carrera manual, it says that the Fuchs alloys are manufactured out of an aluminum-magnesium alloy, but it doesn't give any percentages on the composition. The Porsche factory manuals cite the wheels as being "light alloy."

"Freshly polished Mg wheels and fan blades look so much more brilliant than any aluminum wheel, because of the Mg. Pure Al does not polish as well."

That is a matter of opinion, I have never seen a magnesium fan blade polish up really well. The magnesium is almost always porous, and leaves little pit marks when you try to polish it.

Again, you have interesting theories, but you have no information or facts to back it up. Citing the Bentley manual as a definitive reference is pretty weak.

It would seem the only way to really tell the composition of these wheels is to do a weight/density test. Anyone want to dip one into a bathtub?

-Wayne

[jmohn]

As anodizing magnesium is a much more complex and less effective (as a protectant) process than anodizing aluminum, I submit the wheels are predominantly aluminum.

Jerry M
'78 SC

[nick-moss]

I have to agree with the majority here that Fuchs are Aluminium rather than Magnesium. Here is the relevant section from Paul Frere's 911 Story

[Wayne 962]

Hmm, once again, Paul seems to set the record straight. What a great historian - loads of detail there.

-Wayne

[Zeke]

Opinions abound here while fact is apparently scarce. With that in mind, I feel I'm allowed an opinion, as I have no facts to present. But, I tend to disagree with the statement that aluminum doesn't polish as well as mag.

Many, many years ago, I purchased a set of Halibrand magnesium alloy wheels during the era that Shelby was using them on the Cobra 427. Halibrand plated them them with some kind of funky gold anodize or whatever. I'm not a metalurgist. They would corrode at the drop of a hat in the natural. I have to agree with Wayne at least to say that Halibrand's alloy did not polish well, was porous and would hold a brilliant shine for about a week.

On the other hand, I have some polished aluminum here and there on cars that you can count your eye lashes in the mirror like reflection. It seems to hold up fairly well. My Fuchs must have some mag in them, because they do go away in a few months. But they are far better for a stable shine than those Halibrands.

Now, you want a good laugh? I bought 4 Halibrands for under $700 which was was about a month's pay then, or more than 2 house payments.

[blue72s]

Originally posted by Wayne at Pelican Parts
The magnesium is almost always porous, and leaves little pit marks when you try to polish it.
-Wayne

My R wheels are polished and has pit marks.

They are also *extraordinarily* light.

[nick-moss]

The pitting on your 7R is due to corrosion. The rim was originally anodised, but the anodising till allows some corrosion. When the anodising is removed and the rim polished the corrosion becomes quite obvious.

[IROC]

I think my little Porsche Tech Spec booklet lists the Fuchs wheels as "AlMg" wheels - which lends some credence to the magnesium content of the alloy. In fact, when I first read this, I thought they were magnesium wheels.

There must be a material specification that covers this alloy. I have some European material info - I'll see if there is anything about this...

Mike

[blue72s]

Originally posted by nick-moss
The pitting on your 7R is due to corrosion.

But aluminium doesn't corrode! They're mg, then?

[surflvr911sc]

Originally posted by blue72s
But aluminium doesn't corrode!

We wish!

[GeorgeK]

OK, we *really* need a metallurgist here, otherwise we'll argue ad nauseam, without getting serious conclusions.
Here the back of a 1981 8X16 Fuchs:

[RickM]

Quote: "But aluminium doesn't corrode!"

Sure it does. Aluminum's "rust" is white.

Those of you who have Tobias Aichele's book "Porsche 911 Forever Young" read page 244-247. Not once did I find the word "magnesium".

964 RS wheels are magnesium, but not Fuchs.