I need to put winter tyres on my new XC90 (produced next week and hopefully delivered before Christmas). It is a momentum that comes with 19' standard wheels. Does anybody know if the tyre monitoring device is in the wheel or in the ABS? If it is not in the wheel, it should be possible to get winter wheels without pressure sensors. Otherwise it may be better to change only the tyre and keep the wheels with the sensors, although this may require reprogramming the car. Also any idea if it is worth getting 18' winter wheels? They are cheaper and possibly better on snow/ice. However, can a different size wheel be mounted without having to reprogram the car? I a few words I am looking for the easier way of changing from summer to winter tyres.