The total indicator reading (TIR), sometimes called total indicator run-out (TIR) mentioned for the Fowler QuadraTest Electronic Test Indicator refers to the difference between minimum and maximum measurement. In other words, the TIR measures the amount of deviation from whatever the targeted structure is (flatness, concentricity, cylindricity, roundness). The TIR is the value measured about a particular reference axis. TIR is highly important in preventing excessing stress, premature wear, and a failing system. This is because TIR assesses whether the central axis that is being measured is unequal in direction and/or angle.