Suspension, Steering, and Tire/Wheel Service
Ride, steer, and roll
Suspension inspection starts at ride height. Air-suspension buses use height-control valves; if ride height is wrong, alignment angles are wrong and tires wear diagonally. Check air bags for chafing and cracks, shocks for leaks, leaf springs for broken leaves and shifted clamps, and torque rods, trailing arms, and bushings for play. A worn torque rod produces a dog-tracking or wander complaint.
Steering inspection separates play from lost motion. With the wheels straight ahead and the engine running, measure free play at the steering wheel rim and compare to the OEM limit. Then have a helper turn the wheel slightly while you watch each joint: tie-rod ends, drag link, kingpins, and steering shaft joints. Movement at a joint before the wheel moves is lost motion and is an out-of-service item. Also inspect power steering hoses, reservoir level, and pump drive.
Tires carry both safety and budget. Minimum tread is 4/32 inch in the steer position and 2/32 inch elsewhere, measured in the major grooves. Look for cuts, bulges, exposed cord, sidewall weather checking, and improper repairs; a plug in the sidewall is not repairable. Duals must be matched for size and inflation, because a large mismatch makes the larger tire drag and overheat. Check valve caps, wheel cracks, and rust streaks around stud holes.
Worked rule of thumb: check inflation cold, and remember a tire 10 psi low runs hotter and wears faster.
Trap: a pull to one side is not automatically an alignment problem; a dragging brake or mismatched dual can cause it.