Hi, this is my first post in Car rental programs. I intend to rent a car at SFO late December for approx. two weeks. IIRC most people don't use winter tyres in SFO. Would winter tyres be desireable if driving up e.g. to Yosemite and can they typically be requested at the rental agency? I plan to use Alamo but can still switch to another agency if needed.

Another question about SUV's. I have understood that SUV's are easily given as an 'upgrade'. How likely is it that I will get an SUV if I rent a full size car. Will the likelyhood increase/decrease if I rent a premium car instead? Thanks!