[What'saCobra?]

In the day...

Very few original mag wheels didn't leak air. Some folks varnished or shellaced the interior to cut it down. If it leaked fast, it was always crack-tested, but rarely failed the test. The alodine (original puke greenish/goldish) usually but slowly abraided or fell off in time in the interior.

They rarely failed, though and did take an impact without separating unless it was really hit hard in one place. We repaired a few, but not many. They could be "swaged" or physically formed back into shape if not too awfully bad. Not often and not much. Wouldn't trust them afterwards, but could finish an event. Remember throwing some away. Don't bother, they're gone.

i saw a few rims detonate when too much air pressure was used to "set the bead" or more precisely, move the tire rims out past the drop-center and up against the wheel rim for a proper seal. Usually happened when the wrench didn't use enough soapy water spray on the rim.

They were not tubeless in our racing use. Later, for street use with Firestone Indy wets (a great street tire, wide, sticky enought for aggressive street use, great tread design, great wet stiction and quite illegal in some areas so they were mounted with the print inside), we did use the rims tubeless, but they had to be watched and topped-up very frequently. Tubeless use was mostly too agro to justify skipping the tube.

The tubes were large (the tires were "large" for the day) and it wasn't uncommon to install the tube with a fold, which always caused a leak and a vibration.

Count me in for a set of modern metal mags, though. Actually need two sets. S/C and FIA. Cash on the barrel-head, no "equity investments", naturally.