Magnesium Minilites

[Dave240]

I just purchased some vintage Minilites that are magnesium. I've been doing some reading on magnesium wheels over the past few days, but just wondered if anyone here had experience with them. The seller said they held air fine but the inner surfaces should be cleaned and epoxy sealed before tires are mounted on them again.

I've done searching and found various forums saying to use everything from truck bed liner and rock guard to epoxy primer to seal the inside surfaces. I think the bed liner and rock guard would be a bit tactless - adding weight to light wheels and probably messing up balance in the process. However, epoxy primer may be an idea.

Anyone have experience with magnesium wheels on their Elan?

[EdHolly]

Most racing cars of the 1960s onwards run magnesium wheels - Brabham - Lotus - Cooper - Elfin etc etc. Having had a few of these cars over the years I have found that some do loose pressure others don't.

For instance - I bought a brand new pair of rears from the US for the Lotus 20 and when I painted the exterior with the tyres on, the next morning I had a couple of 6 inch perfectly formed blisters unbroken and standing about an inch out from the metal ! Needless to say they lost pressure at a rate of about 2 to 3 psi a week.

The best process for sealing wheels is to have them Locktited - a process of resin impregnation done by vacuum at the Locktite factory. However don't then damage the wheels as they are very difficult to weld afterwards.

The process I use now is a simple epoxy paint liberally coating the inner surfaces of the rim. So long as it covers the whole inner surface it does the trick for me - since doing this haven't had any more "leakages".

Ed

[StressCraxx]

Hello Dave,

It pays to be cautious about magnesium. I have a set for my Formula Ford. They are the original wheels supplied with the car and so are almost 40 years old.

The challenge with magnesium is its hunger for oxygen. It can corrode quickly and become very brittle. Below are the instructions I was given for my wheels by the man who designed my Formula Ford and fabricates parts in mag, aluminum and other alloys for Indycar and F1:

First get them cleaned by abrasive blasting and non destructive inspected, such as fluorescent dye penetrant (Zyglo) or x-rayed. An aircraft component inspection/repair station can do this for you or a really competent race prep shop. Expect porosity and even cracking indications. If cracked, its up to you if you want to attempt weld repairs by a qualified welder.

Clean magnesium can be treated immediately with a chromate conversion chemical such as Alodine.

Wear gloves, tyvek coveralls, goggles and an organic/acid respirator to do this. Alodine is available from Aircraft Spruce in a quart bottle, enough to do a set of wheels with a brush or sponge.

I painted my wheels with clearcoat paint after the Alodine treatment, including the tire beads and inside rim.
Wear gloves, tyvek coveralls, goggles and an organic/acid respirator to do this. Alodine is available from Aircraft Spruce in a quart bottle. The hazard is chromic acid, hydroflouric acid, and potassium ferrocyanide. It can cause burns to the skin, eyes and lungs. It is a known carcinogenic and mutagenic.

http://www.aircraftspruce.com/catalog/pdf/alodine1201msds.pdf

If I had to do it over again I would have it done by a professional shop.

Regards,
Dan

[Elan45]

Dave,

Congrats on scooping these Minilites. I watched the auction, thought about bidding, but didn't. I have had magnesium wheels since the late 60s. My first pair were American Silverstones for my Mk1 Sprite in 1969 or 70. I autocrossead the car and the previous owner of the wheels did too. He had painted the wheels in exhaust system VHT white paint. I don't know why, but that paint is still on them. Seems to have protected the wheels.

Since then, I've had more American Silverstones, 15" wobbly webs on my Eleven and 13" wobblies on my Lotus 20/22 and true 26R wheels on an Elan. I initially primed (Ditzler DP40 in the late 1980s) and painted most of the Eleven wheels, polishing, then clear coated the rim. They were beautiful for about 2 years. Then, the clearcoat became milky and pealed off.

I also think the earlier versions of DP 40 epoxy primer had an etch primer component in them and eventually, the whole wheel looked like I had spilled brake fluid on it. I investigated this about 2006 and I think later DP40 formulations do not have the etch component. Not sure if Ditzler still makes DP40. On my 20/22 wheels, I painted the rims with silver before painting the rest of the wheel yellow and that seems to have worked well enough. Gets me the appearance I wanted.

So I would use a good quality epoxy primer and paint all over.

Roger Sieling

[Dave240]

Thanks for the very helpful advice! Anything to look for specifically in a epoxy primer?

I know there is a local company that does soda blasting and other types of media as well, walnut shells I think. I'll give them a call and see if they would touch them. And I have a buddy who does non destructive testing so he will come in handy.

Thanks again!

[el-saturn]

i'm a bit off base i guess; BUT whenever i read about mag wheels no-one ever encouraged the use of these
brittle antiques!............ it's oxygen, it's more so the fatigue as i see it and I would least worry about them leaking!
PLEASE add your comments gentlemen this topic could be life saving! PLUS minilites were always an after market product which Colin and the boys never supplied, as far as i know - good luck though. elan had to stay at home due to weather. cheerio sandy j

[RogerFrench]

Back in the 60s I had genuine, original magnesium Minilites from Tech-Del and they came with warnings about not using them for too long.
From what I remember the castings were porous, and also had a tendency to form pockets inside - something to do with casting techniques and the way they cool from outside to inside. In any case, the combination of porosity and pockets led to corrosion inside the wheel, invisible from the outside and apparently not easy to detect. They also got brittle with age.
That was then and maybe today corrosion detection is easier - I don't know about the brittling effect, but any reference I've seen to these old wheels is that they're fit for static exhibits only.

[el-saturn]

thanks roger - that?s how i see it and you didn?t even talk about wear: just try thinking about
what could have happened to these poor little suckers!! back in the sixties or beginning of 70?s
those who owned magnesium minilites were chasing the cops! have a nice evening - sandy

[StressCraxx]

The info I posted earlier is from my anecdotal experience. I was concerned about using my old Sterling mag wheels so asked the car's maker his views. An x-ray should reveal voids and inclusions. Zyglo will reveal porosity and surface cracks. The chromate conversion coating protects the metal from further corrosion from oxygen. Paint or epoxy preserves the chromate conversion coating.

20+ years ago I helped a super seven owning friend to replace all of his dampers and springs. We spent the entire day removing the old dampers, cleaning everything, painting the springs, installing the new dampers and setting the spring perches as close to the original ride height as possible. We didn't have scales to set corner weights.

I was about to reinstall the right rear wheel (an original minilite) when I noticed a black strip along the back side of the rim near the rim edge. At first I thought it was race tire clag, but it would not peel off. I pushed on the rubber and realized I was pushing on the inner tube! The inside edge of the rim had split a crack about 1-1/2" long and 3/16" wide. My friend and I were both stunned. He had raced the car the previous weekend at Sears Point. Had the wheel failed on him at speed, the outcome could have been bad. He put tubes inside the Dunlop race tires because they lost air really quickly, over a day or two.

That said, there are lots of vintage race cars running mag wheels and mag uprights, up to 1000HP CanAm cars. There are old warbirds still flying with mag parts that get inspected and treated so they can fly another day. Just know there is some risk. Reduce your risk with proper preparation.

[EdHolly]

My Elan 0425 a series 1 car has used Minilites for many years now, maybe most of its life. Every time I have them off, I check to see if any visible cracks - so far so good. They are genuine mag as a small amount of filing of them lit up as mag does.

Years ago I bought an Austin 1800 for bits when I raced an MGA - and it was on mag minilites and they were totally had it, cracks in just about every spoke of every wheel, yet the thing was still being driven on them, right up to the point where I bought it ! They came in handy to mount on the Lotus 20 with adapters to turn it into a roller before they went to the scrap metal man.

Ed

[el-saturn]

..what i really like is the lovely elan at home - or just where elans always feel at home: at or on a circuit having fun
with the boys - alpine greetings sandy j

[StressCraxx]

RE: Thinking about magnesium vs original steel Lotus wheels:

Because of Chunky's requirements to "Simplicate and add lightness" and "Get the pounds out of the cars" mantras, I think its prudent for an owner to inspect their wheels, suspension parts and chassis attachment points.

I have retired my steel K/O wheels because they are bent and the pin drive holes have elongated.

Regards,
Dan