Sheesh .... it's true-confessions time. Ever since discovering Autopia, I've been meticulous about tire-cleaning. I used P21S for a while (til running out of it), then APC+ diluted according to label directions -- using a stiff brush -- and typically I'll clean, rinse, clean, rinse ... til I'm getting no dark-colored rinse-off residue. After cleaning, I've used Eagle One Satin on the Benz, Zaino Tire Treatment on the Jag. And in the last couple of weeks, I'm discovering that, after a wash but prior to dressing, the edges of the tires are really brown -- more brown than I ever noticed before I started these "good" cleaning/dressing procedures. So if anybody has info/insights, I'll be eager to hear them.