Measuring students' reading motivation is a common practice in literacy classrooms, and results often inform instruction. This mixed-methods study problematizes this practice, raising tensions between how reading motivation is measured and its enactment in a reading class. Key tensions include reading motivation as competition versus a collective endeavor, reading motivation emphasizing teacher-directed learning versus student-led learning, and reading motivation valuing texts as windows versus mirrors. The author suggests that teachers should take a critical lens to reading motivation measurement tools before using them.