You shouldn't have to expand the clamp opening to mount any of the standard Nitto 25.4 mm track bars. You WILL find that you may have to rotate the stem around to find the position at which the bars slide through it -- the stem has to be behind the bars at one point, in front at another, etc. Just feed it through gently so you don't nick the bars and if it doesn't slide right through, back off and try another angle. This ain't rocket science.