2nd flat in 2nd week

[OakLeaf]

+1 to what everyone else has said.

Sometimes repeated flats are just a coincidence, sometimes they're a result of riding on really debris-filled roads, but sometimes they're a sign that your tires are due for replacement. (At least if both flats were in the same tire, which you didn't say, and most of us seem to be assuming.)

Since you bought the bike used, do you know how old the tires are? Are there any signs of dry rot? If it's a treaded or knobby tire, how much of the tread or knobs is left? If it's a slick or partial slick, when you had the tire off to change the tube, how thick/thin did the center part seem? Without air in the tire, did the center of the tire seem concave?

[lph]

Oh, and random piece of trivia: I changed my old, splitting tires for another set of the exact same type, only virtually unused, that I had on my other mtb. Just for kicks I weighed them both. Over 100 grams of rubber worn away!

[gingerale]

I had 3 flats in 2 weeks recently and was so frustrated. One was because of a piece of glass the size of a grain of kosher salt. Sliced right through my tire and into the tube. The girl at the bike store told me that some people would be thrilled to have only 3 flats on one ride. I actually carry 3 tubes with me now but I figure if I get 2 on one ride again then I'm heading home. lol