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Kirkham Motorsports

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  #21 (permalink)  
Old 09-15-2020, 04:43 AM
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With respect, why attempt to repair Mg wheels? Most of us have replicas, not original Cobras, and aluminium alloy wheels can be made to look like authentic vintage Mg wheels, so why not err on the side of safety and stick with aluminium alloy wheels?

nota bene...a 275/60 x 15 tyre weighs around 30lb / 14kg, and a 15" x 9.5" aluminium alloy wheel is only around 15lb / 7kg

That said, I understand the desire to go as "authentic" as possible in certain areas.....but if safety is a concern....

Cheers, and stay safe!
Glen
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  #22 (permalink)  
Old 09-15-2020, 09:18 AM
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Disclaimer: I am not an expert. You need to speak to the “right” Cobra experts of the period. People like Lynn Park. Fran Kress, JL Henderson and others whose names will be referred to you by these people and people on this forum.

Now, I did research the period Halibrand wheels for the Goodyear tire history I wrote for SAAC a couple of years ago and learned a lot about the original Halibrand magnesium wheels.

Before I go into that, we need to know more about the wheels you have.

You say you have “a set of old Halibrand magnesium wheels”.

You have to be more specific than that. Old as in 1965 or 1966? Which style Halibrand? You’re sure they’re Halibrand.

In any case, “old” is not good when talking magnesium wheels. Age embrittlement, stress cracks (visible and invisible), and corrosion are your enemies.

Halibrand, as good a manufacturer as they were, did not have the modern metallurgy technology in the 1960’s we have today.

Age embrittlement can take place with a wheel just sitting on a shelf for years. Add heat, UV, ozone, corrosion and stress and you have a cocktail for disaster.

OK, lots of guys are running period magnesium Halibrands in vintage racing, but as you have read in the previous posts they are carefully and meticulously maintained.

Running old, unknown magnesium wheels (one which already has a crack) on the street is probably not a good idea, earning on the side of caution and safety.

The Dow coatings, mentioned in previous posts, applied to the magnesium wheels were intended as corrosion protection (not air sealing) and had a limited life. Simply reapplying a “new” coating of the Dow coating (or other coating) without being assured of the internal condition of the casting (corrosion and stress cracks) will only mask an impending problem.

Now regarding mounting, bead sealing and inner tubes.

Keep in mind that those 1960’s ish Halibrand magnesium wheels were intended for racing due to their light weight. Racing tires were replaced frequently and any sign of wheel damage relegated the wheel to the scrapheap. Lots of broken/cracked Halibrand magnesium wheels hanging in garages as garage art (mine included).

And the period Goodyear racing tires were intended to have tubes to insure sealing and to keep the light weight tires/beads on the rims. (it is a challenge to find modern tubes with valve stems that line up well with the old Halibrands but the previous posts here about the tubes may help).

And, regarding the bead sealing. Not all bead sealing lubricants/sealers are created equal and some can quickly promote corrosion on magnesium and aluminum wheels. (ask me how I know LOL)

The period expert on tire/tubes would be JL Henderson, (Shelby’s Goodyear Racing Tire manager for 46 years now retired). He would be a wealth of information.

Most tire/wheel stores will be of no help. Contacting a high end (Ferrari or restoration shop etc) dealer to get a tire mounting recommendation (relative to bead sealing compounds that do not cause corrosion) might help or of course a Goodyear Racing distributor like Roger Kraus will be a big help regarding tubes.

And I wouldn’t even broach the subject of welding repairs of cracks etc without a very thorough crack and corrosion inspection and finding a very competent (aerospace or racing) weld shop with experience in magnesium repair. No fireworks wanted here. Epoxy repairs will just hide/promote corrosion

So, OK, lots of guys back in the old days ran magnesium wheels on the street. But keep in mind performance upgrades of the day were passing fancies and short lived. They weren’t running a magnesium wheel for 60 years, or 60 months and probably not even 60 weeks.

So proceed with a great deal of caution.

Unless your car is intended for high end concors shows or museums, or carefully maintained vintage race cars, running ”old” magnesium wheels on a street car may not be prudent.

Lots of very nice modern (aluminum and some as mentioned magnesium) reproductions out there.

That’s my 10 cents worth.

Cheers
Greg
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  #23 (permalink)  
Old 09-15-2020, 04:31 PM
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I'm certainly no expert either, however Greg has way more information and knowledge on the subject of old mag. wheels than I do. Safety should always come first, particularly when the subject is Cobras.

My 1 cent worth

Cheers,
Glen
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Old 09-16-2020, 12:05 PM
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Greg is right safety 1st.
I never repaired any wheels, crack check yes. My feeling is cracked wheels should be repaired by a qualified individual, which will be at great cost.
Best rule if cracked = wall art!

Last, they are a wheel that requires PM, Lynn and Fran gave me the tools on that which I have shared. Oil Oil Oil and look at them to be sure they are good.
If cracked you will lose air. If not they may seep but will hold over time.
If you dont want the headache buy alloy!

Oiled and not pretty, Mags on AC#1085
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Last edited by 1985 CCX; 09-16-2020 at 12:09 PM..
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