[PsychoSlug]

Just purchased a CPO 2008 X5 4.8i with the 20" wheels and performance tires. Obviously I'll be purchasing a winter setup later this year.

I'm planning a road trip to Montana in late September, early October. The total trip entails about 4,000 miles round trip, most of which are on the interstate. I'll likely encounter a few gravel roads, and a little snow is possible that time of year, although typically only in the higher elevations. The weather is typically in the 50's and 60's and beautiful that time of year.

Would you swap over to an 18" winter setup before the trip, or wait until after the trip? One of the best roads around is out there, and I'd love to drive it on the performance rubber. I just worry about the weather taking a turn for the worse, and being stuck on summer tires.