Having just aquired an ST that has only done 12500 km, I am thinking of replacing the Metzelers on it. They appear a bit hard and were supposed to have been fitted at 10000km about two years ago. Not sure about all these "facts" and the rear has a fair ridge or flat spot. I think the safest way is to put newbies on even though quite good tread is left. Comments from those who have been here before. Thinking of PR3 or 4.(if available)Ppopeye