Sirion 2009 power steering problem


I own a new 2009 Sirion 1.3 and I put new alloy wheels 6.5x15 with 185-55/15 tyres on it(It had the stock steel wheels with 175-65/14 tyres).The problem I'm facing is that since I put the new wheels and tires on it the power steering in parking manuevers stucks momentarily like loosing power assist.It does that only when it is not moving and sometimes not always.The service man in Daihatsu dealership told me that the problem is the wider tyres.Sirions with alloy wheels fitted from the factory the have different rack and pinion steering.Does anybody knows anything about it?Any help welcome.Thanks