Even though I've had some really crappy tires down thru the years (which I have used to drive long distances on highways), the only time I ever had a flat tire on the road was around 1997 or 98, I was just getting started on the highway on the way home from work in my '55 Sedan.
I opened the trunk and there was this ancient 670X15 spare, dry as a bone and it was flat also. Just as I had finished removing my flat tire, an '85 Crown Vic stopped on the shoulder in front of me. An old man got out and offered to let me use his portable compressor that operated off the battery. We aired up my spare and it looked more and more scary as you could see the dry cracks throughout the sidewalls. I put it on and thanked the Lord, that he sent that man out of the blue to assist me. I drove 29 miles the rest of the way home on the highway, trying to keep the speed under 55 MPH for fear that the old tire would fly apart.
It held up all the way home, even though it had a un-even load on it, since the other three tires had an equivalent O.D. of 710X15's. So she ran down the road a little lopsided.
Yes, the next morning, I threw my spare in the back of the pickup truck and dropped it off at a tire shop to get plugged. That night, I removed the old spare and put my plugged tire back on. I'm guessing that old spare had to be well over 35 years old. It wasn't a Coker. It was a name brand. But at that age, yeah, the rubber is too dry and scary. I was shakin' in my boots for 29 miles till I got home.
