The term run crap basically came from the really stiff extended mobility tires that came on the C5. GM spec'd them so they were capable of 200 miles of zero pressure operation at 50 mph and still be repairable. Those tires didn't handle as well as non run flat tires or as well as other run flat tires. When the original run flats on my 97 wore out I replaced them with the Firestone run flat that was made for the car. I saw the difference right away. I used to go to several autocrosses per year on a particular go kart track. We always ran the same course and I had been running it for years before I purchased the car. With the original EMTs I had quite a few runs that averaged right around 1:31 on dry pavement. The first time I went to the track with the Firestones it was raining and my times averaged right around 1:27. Those fun flats were 4 seconds faster around the course in the wet Vs the EMTs in the dry. Once the track dried out they continued to run at that 1:27 pace.

I was amazed at how much better they performed than the GYs and run flat Vs non run flat didn't enter into the equation.

20 years later run flat technology has reached the point where there is no real performance difference as far as 99% of drivers can tell. The only difference to avoid run flats is if you can't afford the cost. I get a kick out of the people who think a flat is easily fixable alongside the road. If you get a flat in a left rear tire your only chance of plugging it is to have access from the front or rear of the tire which means you will be partially under the car, laying alongside the road with traffic going by 2 or 3 ft from your body. Add rain and night time and you would be a fool to attempt doing that. Much easier and less costly to have a run flat that you can drive about as far as you want at reasonable speed to get to a place where the tire can be replaced at a minimum.

Bill