Too many times to count. At one point I carried 2 spares, but that was years ago when I was running BFG products with their buttery soft sidewalls. Went to the original MT/Rs and lost 1 sidewall. Went to Swampers in '04 and haven't looked back. I've lost a few beads, but never a puncture.
I always carry a full size spare the same way I always carry a first aid kit and fire extinguisher and recovery gear, and tools, and parts, and...
I have dual spares on the Tacoma for the same reason...BFG's. In one year I blew out the sidewalls on 8 KM2's, the America's tire manager hated me. I once got two flats at the same time (KM2's) and even managed to get it on video. I learned my lesson, running Coopers now. If you don't carry a spare, you better remember your walkin' shoes OP!
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