I have just recently purchased two new front tyres for my car, Michelin Pilot Sport 4S (Build date late 2019).
(I think) ever since new or very soon after, I’ve noticed a worn black identical ring around the sidewall on both of them. When freshly washed it looks black, and when unwashed it develops a powdery like substance that can be wiped away.
Does anyone have any clue? Thank you !