MAGK944

Porsche called them Magnesium wheels in their Turbo Cup literature, so what should we call them?

I understand that there were different compositions of these wheels over time but they are still all Magnesium Cup Wheels. Even the set that sold on BAT were identified as such and they had different compositions for the front wheels and for the rear.

In the Porsche literature below the fronts are what the op posted about, same part number with the Si12 marking, yet the factory still describes them as “Magnesium” in their Turbo Cup spec sheets.

edfishjr

There seems to be something a little screwy here and it may be Porsche's fault.

The BAT set of wheels are definitely made from Magnesium. That's what Mg 7 or Mg Al 7 means. ~7% aluminum and 93% magnesium was a standard alloy for wheels that basically stopped the cracking problems that plagued earlier mag wheels. Chevrolet sold 5th gen Corvette magnesium wheels (made in Italy) for a couple of years that were made from a very similar alloy. So did Ferrari. They will still crack and fail a lot more often than aluminum, however.

The pictures in the OP show wheels definitely not made from magnesium. They are aluminum wheels. They may very well have been cast in a similar die as other wheels actually made from magnesium, but they did change the material spec that is embossed on the back of each wheel. It is possible that Porsche did not roll the part number though even back then they were normally very good about incrementing the part number for each change. The actual wheel maker protected himself from criminal liability by changing the material designation. The Porsche part number is none of his business. Part numbers were not controlled by law in the automotive industry back then (like they are in aerospace) so it could be true that Porsche kept the same part number.

To change a wheel from magnesium to aluminum, not roll the part number and keep calling it a magnesium wheel would be fraudulent, IMHO and it is a big deal. It would be like selling steel I-beams actually made from Balsa wood but painted to look like steel. In this case they were painting the wheels with the whitish color that had previously indicated magnesium material because it was originally a special, anti-corrosive coating just for magnesium and you couldn't get it in any color you wanted.

Why this is important:
If you want to weld these wheels you sure better know what the exact alloy is. The procedures and weld-rod to be used are very different.
If the wheels are aluminum, you need take no special efforts to evaluate them for cracks. If they are magnesium and you track them you'd better dye-penetrant inspect (or magna-flux) on a schedule if you want to stay alive. The safety implications are significant.

I have no idea about how any of this affects market value. For all I know the "magnesium-style" wheel made from aluminum is more valuable. But, somehow I doubt it.

I know this is more info that anyone really wanted, but buyer beware is all I'm trying to say.

MAGK944

I agree there is something weird here with the Porsche part numbers, how can two wheels have the same number but one be composed GK-AlSi12Mg and the other GK-Mg7. Also there have been wheels sets sold where the fronts are one composition and the rears another.

My summation fwiw is that the early wheels had more of a magnesium content and later Porsche adjusted the composition to include less Mg due to the inherent risks of the material, yet they kept the same part number. Both were sold as “Magnesium Cup” wheels in their literature at the time. As to the mixed sets what may also have happened is the front wheels were the first modified by Porsche due to the higher heat they experience and they kept supplying the rears with the higher Mg content until stocks ran out. All this is a guess, who really knows.

Anyway regardless, both types are genuine Porsche Magnesium Cup wheels as opposed to regular phone-dials (GK-AlSi7Mg0), whether the early high Mg content are worth more idk, maybe the later lower Mg content, which are much safer yet still Cup wheels, are worth more. One thing for certain, Porsche sure could make things more confusing than they should be. However later during Cup I production they instead conspicuously cast the word “Magnesium” into their wheels to avoid confusion.

racerbvd

These aren't magnesium, they are heavier, the wrong size and the wrong offset. They are a very clean, nicely powder coated 86 (still one year only) 944 Turbo wheels. The guy I got them from thought they were Cup wheels, but Cup cars in 86 where running Fuchs. He said But since, with old Toyo Proxies, the rear when and tire weighs 42lbs, I concluded that they aren't, as they feel much heavier that the ones I use to own. I was really hoping they were, but they aren't. Too bad they won't work on my 87 944S.😪

MAGK944

Trying to figure out this confusion.

So the picture of the part number on the back of a wheel that you posted in your first post isn’t a picture of your wheel, correct?

royalschwarz

I think the confusion is because in the original post, the pic of the part number was taken directly from the BAT listing and is NOT a pic of the actual part number on the wheels being offered for sale.

Also, look at the pics BVD took of the actual part numbers on the actual wheels he bought. 951.362.114.00 which are just standard aluminum wheels. All this confusion and debating could've been avoided if that pic from the BAT auction was never included since it has nothing to do with the wheels being sold. I'm assuming it was to validate the 'Mg' in the composition marking and in some way try and get more $$$ for a standard set of wheels.

royalschwarz

No, it was taken from the BAT auction thomasmryan posted.

MAGK944

Gotcha, wtf

racerbvd

But if anyone needs a nice set of 86 Phone Dials, these are for sale😁

edfishjr

Yes, looks like a "mistake" in the OP. Many other mistakes have been made over the years misinterpreting the material mark, such as thinking that AlSi12Mg meant 12% magnesium, etc.

So, all the standard data looks correct:

951.362.116.00 early offset aluminum 8" front phone-dial
951.362.116.01 late offset aluminum 8" front phone-dial
951.362.116.11 late offset magnesium front phone-dial. AFAIK, this is the only 8" magnesium phone dial

951.362.118.10 late offset 9" rear magnesium phone dial. AFAIK this is the only 9" magnesium phone dial

...and no clear evidence that Porsche ever changed alloy yet kept the same part number