Thoughts on old Magnesium rims

I thought all wheels on the Boxer and Testarossa models were aluminum.

 

you can magniflux...they may still be in great shape. otherwise for blvd cruising only. vintage racers use original mags for show only and usually race on newer alloys or repros.

 

I've only seen it called "light alloy" in the F documentation, and my recollection is that, based on the weight comparison on the 308 wheels, the 308 stock wheels are still mostly Aluminum (like 60% Al and 40% Mg) -- so could be that wheels that have a true significant majority of Mg have more problems. If you want to do a science experiment, you could measure the volume of the wheel (most easily done by putting it in a tub of water and seeing how much the water level rises, and then how much added water it takes to reach the same level without the wheel) and the weight to calculate the apparent density -- from that you should be able to get a rough guess at %Al vs %Mg (there will probably be some misc stuff like a few %Si, but I think that you'd be close enough).

 

from own experience I only can say:

never use magnesium rims older than 15 years for racing. the material takes during the years humidity without you see it if they are not painted. if painted you see after 3 to 5 years that the paint will get off. this because the magnesium is "living".

for show only you may use the magnesium rims, or for decoration, but I would not take them for normal driving when they are so old.

on a fiat 124 spider BS modell I once had magnesium rims about 17 years old. I was driving this car slowly, very slowly on a sidewalk edge and some was broken out. since then I´m very carefull with magnesium parts.

 

I have the same concern on my 79 BB, so what I did was purchased a set of 17's and kept the originals for show only.

 

I believe the wheels on the Pantera are magnesium. There is a lot of magnesium on aircraft.
I know the rear upright castings on some older race cars are magnesium. They are suspect.
I believe magnesium strength is in its surface and when it starts to corrode it looses its safety margin.



Ago

 

In the German vintage car scene, they simply go for x-ray on magnesium wheels...this reveals all cracks...

 

If magnesium is painted and after 3 years the paint will get off, there is something wrong. Most people paint magnesium for protection. Speedline rims for the 355 for example have such a painting, problem's appear when the rims are repainted ... or the "protection paint" is damaged. Incorrect storage will do the rest.

Some years ago BMW "raced" with their new F1 car and the old turbo powered F1 in Goodwood. The old F1 cars had been stored for years and the racing mag wheels just blowed, if I remember correctly they asked Bernie and used some original racing mag wheels form Bernie Ecclestone (he has a large collection of F1 cars and stored the cars right).

But you can't compare racing wheels for F1 use with normal street use alloy-mag wheels. The wheels used in F1 had a thin color coat, very light weight - nearly without protection, these wheels have very high mag content - completely different composition. We have a set of very original, unrefurbished, original factory cromodora painted wheels for our 512 BB (fist owner was Mr. Brand, founder of BBS) there is no "blowing" because the car and so the wheels were stored dry.