Technical
Suspension inspection Tips on checking a variety of suspension components CUSTOMER: “There’s this big clunk when I turn left, is my car unsafe?” Diagnosing ride control issues is relatively straightforward, but newly hired technicians may not know these tips of the trade. This article addresses common suspension component inspections, offering expert advice based on our experience as well as pertinent information from parts suppliers. We’ve been there, done that! Learn from our experience.
By Mike Mavrigian
L
et’s take a look at various suspension parts inspections, including ball joints, wheel bearings, wheel hub units, control arm bushings and more.
Image courtesy of Moog Steering and Suspension/ Federal-Mogul Motorparts
Ball joints Loaded ball joints experience vehicle weight, typically at the lower control arm at the lower arm on an SLA (short/long arm) suspension, which also must be able to pivot in relation to steering linkage and the steering knuckle. On a twinarm suspension, the upper ball joint serves as a follower joint. A strut suspension uses a follower ball joint to connect the lower control arm, steering knuckle and Ball joint wear can be checked the strut. The upper strut for both axial (vertical) and lateral (side-to-side) play. mount assembly
features a thrust-type bearing to support the weight of the vehicle and allow the steering linkage to rotate the strut and steering knuckle. Check for both axial and lateral runout. Axial runout of a ball joint basically refers to the in/out movement of the ball joint stud and ball relative to its ball socket as the stud and ball moves in-out of the socket. Lateral runout refers to movement of the stud ball side-toside within the socket. To check for axial runout on an SLA suspension, support vehicle weight by lifting at the lower control arm. Place a pry bar between the bottom of the tire and the ground to first determine if any axial movement is present. When dealing with a MacPherson strut front suspension, lift the vehicle by the frame or rocker panel support area and test in the same manner. If lower ball joint axial play is suspected, attach a dial indicator to the lower control arm and position the dial gauge in a vertical position on a clean flat spot at the top of the
38 | ASP March/April 2017
