Strange tire issue unique or not?

[Steve Raucher]

So about 3.5 years ago I buy from Tire Rack new Goodyear Eagle tires and mount them to alloy Fuchs, no problems.
Eight months ago I remount and balance on Steel wheels 5.5". Weekly I do my favorite 50 mile loop up into the mountains for spirited drives. Yesterday after parking car up at regular mountain spot after about a half hour I notice the left rear tire is going down. So I put extra air in and baby the car at reduced speed down off the mountain to my tire vendor I've done business with for many years. Well it's a Sunday and they are not "comfortable" with any of their techs removing wheel from Speedster. Even called around to two other local Company locations and no one could help me. So I get car home knowing by morning it would be flat, sure enough it was.
I removed the wheel and took it back to shop and left it to be checked out thinking it must be a valve issue as I did not see any visible nails etc.
I wait about 1/2 hour and the tech says not a valve issue and cannot see any reason why it went flat. So I left it there several hours and he did the water test etc....nothing.
It continues to hold air at 32psi the whole time. Took wheel and tire home and remounted it doubting 1900lbs pressure from car weight will bring tire down again. Tech thought perhaps by remounting and positioning the wheel on tire that may be it?
Anybody ever experienced something like this or have a cause? Steel wheels were brand new and new chrome put on them.
KTF,
Steve

[David Jones]

Speck of dirt in tire valve. Got blown out when re-inflating. It has happened to me more than once in the last 50 years.

[Adam Wright]

Grease the rim around the bead, helps to get a good seat.

[Alex Mestas]

Steve
we had a similar incident happen to my wife’s Lexus. It turns out the original steel rims were chromed by the dealer before we purchased the car new.

Over the years the inside portion of the rim, and the rim edge, the chrome plating had deteriorated by the rim edge which allowed air to escape because it did not sit tightly on the tire bead. Check out the rim edge carefully. It’s not visible when the tire is on the rim.

[Jules Dielen]

+1 on dirt in the valve stem, or repositioning the tire fixed it. Anything else would have shown up with your 'water test'.

[Alex Mestas]

Jules:
unfortunately our leak did not show up on the water dunk test, only when pressure was placed on the rim with the cars weight. Very frustrating.