245/40 or 255/35 on all 4 corners? Factory SS 20s for winter
 

Looking at winter tires, and I've found the ones I want (Nokian Hakkapelitta R2), however they don't have the recommended 245/45-20 size that I was going to put in all 4 corners.

Would I notice any issues going to the 245/40 or 255/35 on all 4 corners? That is, assuming the 255 would fit on factory 20" fronts...

Doing the math, it looks like the tire sizes they have (245 and 255) would be about an inch less diameter for the 245s, and about 2" less diameter for the 255s vs the 245/45, so I'm hoping the 245/40 would work, as the 255s would probably leave VERY little sidewall

Any thoughts? Would a 245/40-20 work for front/rear setup on the factory wheels, or should I look for another brand of tires with the 245/45 available?

I don't live in a cold climate, but my thought is that you'd want a much taller sidewall to protect from pothole blowouts that are hidden in the snow/slush/water. I'd probably get some smaller diameter takeoff rims if possible, and keep the stock tire O.D. or slightly larger. That'll give a bit more ground clearance as well. I'm not sure what the smallest wheel diameter you can put on an SS is. But I'd go to that.

Yeah, that was my original thought as well, but I came across an oem set of wheels for winter with an unbeatable price, do I'm stuck with 20s. Just talked with the discount tire guys and they recommended a different nokian tire that comes in the recommended 245/45, so I think I'm gonna go that route and hope for the best