8cam, JMHO
I'll bet if you look up the temps for where you were that day you may find the answer for the behavior of your 555's.....maybe they are as temp sensitive as the D3's.
I also have to agree with Robert's (
Robert! ) assessment of the D3's about the age factor. The most I ever got out of my D3's was 4.5 yrs & 32K miles before they were worn physically & getting rather hard to the finger nail test. LOL Oh, the only other pro for the D3's I forgot to mention....when you can smell them from your seat, they are ready to give max grip. It's hard to over heat them in most normal enthusiastic street work on the twisties.
Tom