My Lexus RX400h (2007), has recently developed a severe case of road noise which increases to a quite unbearable level by 60mph. The front tyres are new since Jan 2011. They are "Far Eastern" in origin ( 235/55/R18 104W XL ). The rear tyres are Bridgestone and not new but still legal ( 235/55/R18/99V ). Are there any special tyre recommendations for this model ? I was not aware of this nioise until quite recently. I have checked the tyre pressures and they are in accordance with the car maker's recommendation - 32 front and 34 rear.