Help need regarding my car tires

[James Quin]

Hope all the members are good,
I have an issue with a tire from a very long time (about 4+ years.) The tire suddenly started losing air during winter and this has been happening evry winter.
In the beginning, I was putting air into it, going back and forth between spare and regular tire but it just kept happening and it did not stop. About 6 months ago I decided to get a new rim and at the same time get new tires. Everything was fine but once the temperature started falling, into 30s, the air just leaked and I realized that the situation is same. How can it be that it started happening suddenly, got new tire & rim replaced and still happening? Can it be the valve? Even if there are no bubbles coming out?
Any suggestions are welcome.

[BrisPiripi]

Air pressure can vary when temperatures drop and any holes that are fine at normal temperature could cause pressure loss at low temperatures. Checking for air bubbles in large containers of ice water should help

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[kaanage]

They normally replace valves when fitting new tyres. But try a metal valve cap to eliminate this as a possibility.

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[sambb]

what are we talking - a psi or two or 10psi?