Mine has the 225/55 R17 and I am running the pressures per the plate on the door which says 3.0 front 2.5 rear. Mine is the same as Grumpy's plate
If you do move to these size tyres make sure that they are 101 load rated and not less.
I am actually quite impressed with the comfort of the ride with this set up on the Michelin Primacy 3. I have not yet noticed any wear on the centre of the front tyres but now Grumpy has mentioned it I will be watching them like a hawk.