I fitted the present rear Metzeler 7000 km's ago. Approximately 50% of our riding is done 2 up. I run 48 psi in the rear when 2 up, 46 psi solo. Checking the tyre for damage etc last night and I noticed there are some cracks in the carcass, in the bottoms of some of the tread grooves. The longest is about 20 mm (3/4"), shortest being about 10 mm, total number 6 at present, randomly dispersed around the tyre. This same thing occurred some years ago with a new rear tyre on my K100RT, that tyre was a Bridgestone Battlax BT045, so at that time I switched to a Michelin Lasertec and no more issues. I'm about to travel across the continent on this tyre, though I'm extremely disappointed to have discovered these cracks. Anyone have "the good oil" on possible reasons ? I will not be re-fitting a Metzeler based on this, I will revert to the (original fitment) Bridgestone BT020 REINF.