we were told that one of the tires was "separating" (haven't had a chance to look at it yet, as they mounted the spare and chucked the bad tire in the spare holder under the bed).
So we'll see what's going on, as the other three seem to be ok....
Might be a rot issue - was that tire sitting in more sunlight...?
We had something weird happen with one of our wildland fire trucks - a 1 ton single wheel pickup with a 200 gal tank and pump in the bed. It started handling really strange sometimes. One time we were headed down the highway to do mutual aid, and it just started to "come apart" going around a corner at about 65mph. I've driven a lot of old trucks with various issues, but this felt just like you were towing a long trailer that was tail heavy and swinging. For a few seconds I thought we were dead, but I finally got it coaxed around the corner and slowed down to about 50-55 the rest of the way there and back.
The fire chief drove it somewhere and claimed it was just fine, but then some other volunteers drove it and it scared them to death. I thought that the frame must be broke. Finally, somehow it was discovered that the tread was trying to come off of one or both of the back tires.
So our VFD put two new tires on it, and since we got another dually wildland engine from the state, we pulled the tank/pump out it, put an old topper on it, and are using it for a command/service vehicle. It's actually sitting in my driveway right now as we don't have room for it in the fire hall. It drives pretty nice with new rear tires and all that weight off the back.