Ever have this happen? Most of my flats are rear tire...no mystery there. Front tire kicks up a nail that hits the rear tire perfectly and hisssss it's flat. I had two incidents though (same bike and same rear rim) where the nail not only punctured the tire but went clear through the Tuffy rim liner, the tube, and finally through the rim and out. The second time I had to walk to work and use a pair of vice-grips to pull the nail back out of the rim. That rim must be jinxed.