Originally Posted by racingbmwm3

235/65/17 recommended size then. Assuming you have not put a big brake kit on the car.
http://www.tirerack.com/snow/WinterT...&performance=W

I would install the winter tires the day before you leave, re-check the torque on the bolts the day you leave, then swap the 20's back the day you return or the following day. You don't need to worry about wearing your tires out in just the few hundred miles of road trip. I would just avoid driving them everyday in SoCal. A weekend once or twice a month is ok.

Either set of wheels will fill the back of the rig along with having to fold down at least one seat. Better to leave them at home and save your space and gas mileage for more necessary items.