My flats always follow a theme these days: I get a small cut in the rubber, and over time a tiny bit of rock/glass gets stuck and gets slowly through the rubber and casing to puncture the tube. Usually results in a slow leak, which most times I don't hear but instead feel.

The last one was on the first leg of the Mystery Tour just after we left the Preston/Fall City gravel trail. A sharp sliver of rock had wedged itself into a cut no more than 1/8" wide.

Always a rear tire - and I'm grateful, because you never know what's going to happen with a flat on the front.

DD