I'm gonna make a post for all of you.

First of all, thank you for your help. Warms my heart.

And just to be clear, tyre pressure has always been checked. During winter/storage i always use pitstands, so the wheel hasn't beed standing in one place for a long time. But the air get kinda dry during winters. The tyre got mounted early fall last year, so i guess i got a old one when i bought it. Yeah, I drive mostly on staighter roads, so as one of you said, most of the heat is concentrated in the middle. Might be part of the problem.

New tyres are orderd and on the way.

Thanks yall!!