I have noticed similar wear patterns on my PR3's. Maybe it has something to do with the amount of miles I commute vs ride on the highway
I've adjusted my tyre pressures to:
Front: 38 (well 37.9 on the gauge)
Rear: 43
. . . .
I now have about 5000km on my PR4s. I am happy with the grip, dry and wet, but I am now finding that as they wear they are becoming VERY noisy on "course-mix" bitumen. I did not notice this when the tyres were new but it is becoming louder as they wear. On a very smooth surface they are almost silent.
The noise is a hollow rumble, very much like when you roll your empty plastic "wheelie-bin" down a rough driveway. The noise changes dramatically as the road surface changes. I always run 3-4psi above the recommended pressures as I usually have the panniers and/or top box full.
I have just returned from a 3000km trip to "outback" Australia and the rear tyre is noticeably squared off.
The previous tyres were Michelin Pilot Activ (bias belted) and wore very evenly until about 20000km when the rear started to square off. The front tyre still looked very even at the change. I got 27000km out of those and they still had 3-4000km left.
I changed them because I wanted the best possible wet grip for our winter (June/July/August). I have achieved that but am finding the PR4s too noisy. It is far louder than the annoying transmission whine.
At this stage I cannot predict the lifetime of the tyres but my impression is that they may not last as long as the Pilot Activs.
Does anyone here have comments on PR4 noise levels?
Macka
Since Macka also mentions the "annoying transmission whine" maybe he does not wear ear plugs. I hardly ever notice the transmission whine or road noise wearing ear plugs.