Years ago in a previous trailer, it had an undermount spare. We were going to a remote site in the NorCal Redwoods. The last .4 mile into the campground was a 10’ wide “path” where at one point the redwoods on both sides were less than 1’ of the trailer. So we always stopped at the entrance to scope out the “path” to see if anyone was coming as there was no place to pull off and let someone pass due to the close proximity of the trees.
As we were there, a pickup pulls up and asked if we lost a tire. I look under the trailer and the spare was gone. The cable holding it had snapped.
Now the lucky part. The tire was in front of the axles. When it fell, it must have remained completely flat to pass under both axles. Has it tipped up, it could have flipped the trailer.
That would have been quite a ride.