I just came across a very light weight angled (83 degrees) tire valve stems. They even come in a variety of colors. Simply Google "angled valve stems" and there are 2 sites that contain easy to read and good info. One is Throttleworx.com and the other is KurveyGirl.com. Both sell these sophisticated units for less than $30 a pair. My XR screams for an angled stem at least on the rear wheel.