Yesterday I wanted to ride the last 4 stages (52Km) Portugal and I forgot to change my completely used tires. (The note with the red mark is only for repairs).
I immediately remembered this and before I started the countdown for the race, I simply closed the game, hoping that I would be loaded back into the menu. But no, I was loaded for the next stage instead and so the previous stage was lost. (Racenet doesn't show an entry, but the full time (16 minutes) is added up at the end).
I then rode 45km with the worn tires and you can feel the slipping. But the tires didn't break and so I was able to finish the last stages.
But it would make sense if there was a notification for a tire change, just like for a repair.
and this: "the other issue is you need to be able to use worn tyres after changing tyres, currently you lose the tyre set if you change tyres, this is a significant issue"