i'd go up a half size. Black toe nails will happen for two reasons 1. shoes too small or 2. stubbing your toes on the trail. mine are all from the latter <img alt="" class="inlineimg" src="http://www.kickrunners.com/forum/images/smilies/biggrin.gif" style="border:0px solid;" title="Very Happy"><img alt="" class="inlineimg" src="http://www.kickrunners.com/forum/images/smilies/biggrin.gif" style="border:0px solid;" title="Very Happy">