Rim tape smooth?

Checked tires for tiny shards of embedded goodness? (Inside out so that the middle now flares out so stuff can poke out)

Pinch flat? Pressure is too low.

Puncture flat? Pressure too high.

Pressures you're running at? I had all sorts of problems at 120/90/115. 105 seems to be perfect for me. No flats since running 105psi back in September of last year.

Are you purposely running over the tracks? "Hop" to lessen the sharp pressure that that would entail.

Pumping up before every ride?

Good tires? Cracked? Old? Flat?