I Live in the French Alps and we just had 20cm of snow last night, was a bit crazy on the roads this morning.

Im just about to buy an X5 sport 3.0D with 19" stock rims, I was going to put some Perilli scorpion snow tyres and see how I got on. Rather than buy an extra set of 17" rimms.

How is the X5 on the 19" rims with Snow tyres. Some of the hills are quite steep round here and I could see myself in a 4 wheel wheel spin sliding backwards.

It's not get for tires to keep mounting and dismounting them. If you're going to use snow tires, get a dedicated set of wheels for them. 19" wheels with snow tires work fine.

As long as you don't have a staggered wheel setup, you should be okay - it's just that the cable assys(vs chains) may not fit the wider tires - steep roads with snow & ice almost require you having extra traction - some of the roads in the Rockies require snows, chains, & 4-wheel drive in certain conditions