It's been tested. You don't have to go fifty, that's the brand's lawyers' number.Used roadside assistance with the second incident. A spare would've helped, but it also would've sucked driving 50 (as is usually recommended on a spare/donut) on an interstate where everyone's going 70-80mph.
We find out whether spare tires affect performance using a Ford Mustang GT.
I recall a more involved test from Car and Driver in the 90's. They drove for hundreds of miles on donuts on FWD & RWD cars moving the spare around to all 4 corners.