Abstract: A method and apparatus that remains onboard a tractor and semi trailer vehicle for readily providing axle alignment instruction to an operator. The apparatus includes at least one indicator (28) for detecting an axle's thrust line relative to the vehicle's centerline. At least one sensor (40) for detecting the position of indicator (28) relative to the position of sensor (40). Upon axle deviation, indicator (28) position changes relative to sensor (40). Sensor (40) detect the change in the position of indicator (28). At least one signal is generated and transmitted to at least one receiver (68). Receiver (68) communicates the relation between indicator (28) and sensor (40) as alignment instruction of a particular axle (front or rear), particular side (left or right), particular direction in which to realign the axle (forward or rearward), and concludes when the axle's alignment is correct.

Abstract: The present invention is a method with a 3-dimensional measuring apparatus for determining vehicle suspension parameters, which include roll center, scrub radius, etc. The apparatus measures the upper and lower control arm pivot locations, which include coordinate planes X, Y, and Z, where X is longitudinal distance from front axle centerline, Y is height above ground, and Z is distance from vehicle centerline. Suspension measurements are provided by at least one lower support (23a), at least one vertical member (24a), at least one horizontal arm (26a), and at least one indicator support (22) located at a ground plane in proximity to a tire's tread. Indicator (BC?) on indicator support (22) indicates at least one lower steering pivot location determined by horizontal arm (26a). Wheel pivot locator (21) connected to indicator support (22) locates kingpin trail (C?) and provides a way for measuring the scrub radius between kingpin trail (C?) and tire centerline (E).