Lug Nut or Valve Stem Issue?:

Flat tires caused when valve stems have been knocked off by lug nuts during pit stops have been a recurring issue for teams this season. The #19 of Joe Gibbs Racing driver Carl Edwards, the #27 of Paul Menard (Richard Childress Racing) and more recently, the #4 of Kevin Harvick (Stewart-Haas Racing) are among those that have been affected by the problem. According to some in the garage, the problem isn’t that the lug nuts occasionally strike the stem during a tire change. Instead, it’s how the stem is seated in the wheel that makes it easier to be knocked off. “I don’t even know how to fix it,” Rodney Childers, crew chief for Harvick, said after Sunday’s race at Michigan International Speedway. “Definitely got to do something though.”(NASCAR.com)(6-19-2015)