thnx

... according to the US specs, you get a spare as standard, and run-flats as an option.

Very good news since runflats reduce the overall curb weight a bit.

RFTs are bad news! The car will lurch all over the road like a motorboat and can sometimes be dangerous when corners are bumpy from the winter weather. Most European Z4 owners have replaced them. Check out the Z4 forum or any BMW forum, or just ask an owner.

At least those are the choices with the 18" wheels IIRC. The mobility system (fix a flat and an air pump) comes with the choice of performance tires.

I thought the runflats are actually heavier than regular tires. Self-supporting Tires (SST) have very firm sidewalls and make the ride harsher, based on many posts from BMW owners.

The mobility system sounds better. BTW, the Z4 has different size tires, front and rear. Couldn't carry two spares even if you wanted to.

Based on the Canadian order guide at least, the all-season options are runflats, while the summer performance tires have the mobility system. Net result: no spare either way.

Since the Audi USA site is woefully devoid of real information at this time, I looked @ Edmunds. This applies to Cpes or Roadies: if 2.0 T then 17" Run-flats are std., 18" alloys can be had with R/F or Performance. If 3.2Q, then 17" performance are std. but without any valid authority I would bet that 18" alloys can be spec'd with R/F or performance. My choice would be 18" with performance and spring for winter wheels w/ snows.