Hello, two tires about a year old (vehicle is an Audi A3 2.0 TDI 12/2003 with original factory rims) are in the morning on some days completely without air; sometimes the one, sometimes the other, sometimes both. Sometimes a month or even two months is nothing, then again one or twice a week. Was so in the winter but also now in the summer. No nail, crack, scraping by curb contact or similar to discover. Very strange; I don’t know what’s going on : ( Thanks for a few useful tips!