Wow! Great conversation! Thanks for the proper definitions- I do have cloth rim strips- had plastic previously and that was definately the cause of multiple flats on my rear tire so that problem should be fixed. And now that too low tire pressure has been brought up, I believe that may have been a cause of my double flat situation. And I do realize that sometimes it is just bad luck- I also ran over a huge carpenter's staple once- but this frequency was more than just that. Thanks for all the help!