If they are run flats, they work for sh!t
I had a 2003 M3 Convertible, sold as having run flats. I got a flat on the 10 west in Los Angeles. I was already moving slow, say 35-45 because, traffic.
I moved to the right lane, took the first exit, I think Washington, and a tire place was in sight. I drove there, and in those 5 miles at low speed, the rim was pretty much mangled.
So, if those Conti's were actually runflat, they did a shit job of running while flat.
In my 2008 M3 Sedan, I was heading south through the grapevine, and had a pretty dramatic blowout at speed. I quickly pulled over.
I continued in the emergency lane at 15 mph or so, but the tire was clearly not doing the right thing. I stopped and called BMW roadside (2 AM). By 5 AM, they finally found a tow truck to come get me and take me to Valencia BMW.
$850 and 24 hours later, I had a new tire mounted and balanced. There was no way that "runflat" tire Michelin Pilot I think was gonna make it very far.
Both cars were billed as having run flats by the dealership.