I don't really understand you, I'm afraid. The text on path uses a special first margin/ right margin property (after the mask path has been assigned it becomes active) to align with the path. Changing those values will allow to center the path in case the default center align paragraph style doesn't look as expected. For animating the tracking, you will have to use a text animator, not the options in the characters panel.
ok solved...there was a problem with the anchorage point that wasn't in the center.