I'm awaiting delivery of my 2015 Audi A4 in snowy Canada. It will be equipped with 255/35 R19 performance tires which I believe are not great on ice and snow so I'm going to have to switch to winters pretty quick. My tire dealer tells me that I should go to 18 inch wheels for winters because the 19 inch size will be a problem if I wreck a tire and need it replaced quickly - because dealers don't stock much of that size. Any thoughts?

 

Dealer has right idea, but go to a one inch smaller wheel.
Just be sure to get a B8 wheel with the larger hub bore diameter. B7 and earlier will not fit.

Recommend you go with 225/50-17 snows. The increased sidewall is added insurance against sidewall snake bite punctures and bent wheels should you hit a pothole or other hard edge.

The most common A4 tire width is 245, I use the old rule of thumb of two sizes narrower for snows. The goal is to not float on 1-2 cm of road slush and increase the tire's normal force in snow. I've had friends with 245 snows on a B8 A4 complain of slush-plane-ing and being tossed around with plow ridges. You will lose dry road performance, cornering and braking, but it will still be beter than those summer tires in the same conditions. Winter rubber compounds stay flexible even in bitter cold temperatures, where the summer tires are useless below around 5°C. Snow tires will start to slide, if you back off they'll hook up again. Summer tires will just snap into a slide and they will not hook up again, leaving you with that "helpless at speed" feeling.

225/50-17 are also a very common size, cheaper than 18".

I'm in upstate NY east of Lake Ontario, we get a bit of snow and other states of non-liquid water.
There's nothing like a Quattro with snows in a storm. The other un-prepared vehicles on the roads are mere obstacles. I've pushed snow over the hood to the windshield in the driveway before, while my neighbor watched with jaw dropped.

In winter driving, a Quattro without snow tires can AIM where it wants to go, but a Quattro with snow tires can GET there.

 

Thanks TorsenTaxi2 - exactly what I was looking for. A new wrinkle - I'm going to be spending 6 weeks or so in California and will need winters to get there but concerned about a lot of miles on dry pavement while there. Any thoughts on the Nokian RW3 all WEATHER tires (as opposed to all-Season) that are advertised as being good on ice and snow as well as dry pavement? They have the winter ice crystal icon designation.

 

Sorry, that should have been Nokian WRG3 All-Weather tires, not RW3..

 

would you get an audi rs4 or an audi rs6?