I had a left front go flat before, 215/35/18, well before I jumped on the freeway. I felt the front end push a bit on a tight right hand freeway on ramp. Since it was the maiden trip on the tires and wheels, I thought maybe it was just the nature of those particular tires. I drove on the highway for 7 miles at 85-90 mph. The tires were noisy from the start, when I changed lanes and run over the botts dots, the sound grew from a rubber tire clunking sound to a harsh sound of the rim hitting something solid. The tire noise also got very loud. So I pulled off the freeway not knowing what exactly could be wrong but I just hoped it was a flat tire and nothing worst. Oh and when these go flat, they don't go thump thump thump down the road the way regular profile tires do. They just get louder, and if you're on a straight long stretch of highway with any lane changes with the stereo really loud, may not ever even know untils the tire shreds.
At the gas station, even completely flat the tire looked "ok". Was a bit difficult to spot if it was even a bit low on air because of how low profile these tires are. Anyhow, I aired up figuring it was a fluke and got a flat again another 4 miles down the road at another gas station. Completely flat. I aired up the spare at the gas station and tossed it on. BTW, some hub centric rings are a bitch to get off. I basically mangled my aluminum ones to get them off so the spare would fit. The front wheel also fit in the trunk without any issues, pretty lucky.
Driving on the spare sucks. It's loud and obnoxious, seemingly out of balance, the handling is pure crap, and it's embarrassing. Perfect design for a spare I think, except for the out of balance but overall it does help keep your speed down to 55-60 mph and forces you to fix your proper wheel asap.
Oh and the spare does fold back into it's original shape and size. It's a very neat design and interesting to watch when airing it up. It takes the exact same shape as a wheelbarrow tire. I could never of imagined a car spare tire like that until I actually used mine.
Oh yeah, brake clearance will be a huge issue. Stock size calipers and rotors are ok. Anything larger than stock and you will be screwed because the spare won't fit over the brakes. Stock spare must match the stock brakes. To my knowledge there are 2 variations.