Back in the days of One Lap of America, some Goodyear (IIRC) engineers entered a car with FOUR of those mini spares and drove it the whole distance at regular highway speeds with no problems.
I put 1300 miles on one in a rental car once and didn't spare the horses.
The coolest thing was I found one from a full size car that was exactly the same diameter as the regular wheel on my Hyundai, and it had the same 5 on 4 1/2" bolt circle. I put 630 miles on that one, speeds up to 90 (Utah interstate).
You just have to keep them inflated. And NO burnouts!
R.