I ran an "autocross" in my street driven '71 Datsun/Nissan 510 sedan with a 1600cc motor, was unfairly classified upward due to lack of entries, and had to run against 240 Z's...........2400cc motors....... course was a mile long with blind curves, hills, the corvettes were hitting over 100 on the almost straight section, and to win, you became airborn over the hill, and had to land with the car set up for the 90 degree left hander at the bottom of the hill, leading upward to the finish line.
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The first run was one of the most perfect runs I ever made, shifting, drifting and when the car landed, it was set up perfect for the left hander, with the tires lightly squeeling, protesting under threshold braking, I drifted it right up to the absolute edge of the asphalt, squeezing every smidgen out of the pavement, squeezing every smidgen out of the car ..........................
and was within ONE THOUSANDTH OF A SECOND of the faster cars.
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No problem. I had 2 more runs. I was going to air up one of the tires, and go kick their butts!

As I was adding air, I saw a small crack at the base of the rubber
valve stem. I tilted the stem to get a better look, and the tire valve broke off in my hand! I took that as a message from God that I was done for the day.
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By the next year, the officials had moved me up in class, and I started racing on the East Coast where they didn't know me.

........................................yet.-Bob

That car has been rusting in my garage with the tire dust of my last autocross still in the fenders.