Suspension and Steering Inspection

Suspension and steering parts keep the tires on the road and the wheels pointed where the driver wants. They wear slowly, so drivers get used to the change and rarely notice how bad it has become. A worn ball joint or tie rod can let a wheel collapse or lose steering control. This inspection also protects the shop, because an alignment on loose parts will not hold.

What You Will Be Able to Do

• Name the main suspension and steering parts and what each one does.
• Check for play at the correct wheel positions, and say what each test isolates.
• Spot worn dampers, mounts, springs and bushings.
• Measure ride height and explain why it matters.
• Match a noise or handling complaint to its likely cause.

How the System Fits Together

The sway bar, also called a stabilizer bar, ties both sides together. When the body leans in a corner, the bar twists and resists that lean.

Warning: Springs hold a large force. A coil spring on a strut can fly off with deadly force if the strut nut comes off while the spring is loaded. An inspection does not need you to loosen anything. Replacing a strut needs an approved spring compressor and training.

Before You Start

Use the correct lift points for the test you are doing. For many ball joint checks, the suspension must hang or be loaded in a particular way, so the jack or lift position matters. Check the service information.

1. Road test first if the complaint is a noise, a pull or a wander.
2. Note tire wear on all four corners, since it often shows the problem.
3. Look for fresh shiny metal, which shows where parts have been rubbing.
4. Check that the steering wheel is centered and the tires are at the placard pressure.

Testing for Play at the Wheel

With the wheel off the ground, grab the tire and rock it. The position of your hands changes what you are testing.

If you feel play at 12 and 6, have a helper press the brake pedal and rock it again. The brake locks the hub to the knuckle, so bearing movement goes away. If the play stays, suspect a ball joint. If it goes away, suspect the wheel bearing.

Compare the two sides, and watch the joint itself rather than the tire. A pry bar can help you load a joint, but do not lever so hard that you make a good joint appear to move.

Ball Joints

Ball joints are safety parts. If one separates, the wheel can fold under the car.

• Check the rubber boot for tears and leaking grease. A torn boot lets in water and dirt, which destroys the joint.
• Look for movement at the joint as you rock the tire.
• Know whether the joint is load-carrying or a follower. A load-carrying joint supports the vehicle's weight, so it has to be unloaded to check it. Check the service information for the jack position and the allowable play, because some joints allow a small amount of movement and others allow none.
• Some joints have a wear indicator, often a grease fitting that sinks into the joint body as it wears.

Tie Rods

Check inner and outer tie rods. With the wheels on the ground, have a helper rock the steering wheel a little while you hold each joint. You should feel no knock or looseness. Also, squeeze the rack boot and feel for the inner joint. Any play in a tie rod means the wheel can move on its own, which causes wander and feathered tires, and it can lead to a loss of steering.

Wheel Bearings

1. Spin the wheel by hand and listen and feel for roughness or grinding.
2. Rock the wheel at 12 and 6 to check for play.
3. On a road test, a worn bearing often growls or hums, and the sound changes with speed and when the car turns and loads that side.

Sealed hub bearings are replaced as a unit. A failed bearing can seize or, in the worst case, let a wheel separate from the vehicle. Noisy tires can sound like a bad bearing, so check the tires too.

Shocks and Struts

Shocks and struts, also called dampers, stop the spring from bouncing.

• Leaks. A wet, oily film on the body means the damper's seal has failed and it is losing fluid. A light dust film is usually normal. Replace leaking units in axle pairs.
• Bounce test. Push down firmly on each corner, then let go. The body should rise and settle. If it rebounds more than once or twice, the damper is likely worn. The bounce test is a rough check, so treat a pass as weak proof.
• Physical damage. Check for bent rods, broken mounts and dents in the body.
• Road feel. Look for excess nose dive under braking, body sway or bounce on rough roads.
• Tires. Cupping or scallops around the tread are a common sign of worn dampers.

Strut Mounts

The top of a strut sits in a mount with a bearing in it. A worn mount typically causes a clunk or knock when the steering wheel is turned, especially at low speed or over bumps. Have a helper turn the wheel while you rest a hand on the spring, or look at the top of the strut. It should not jump or bind.

Bushings and Sway Bar Links

Control arm bushings are rubber mounts that connect the control arm to the frame. As they age, they crack, tear or separate. A worn bushing lets the arm shift, which leads to clunking, steering wander and alignment that will not stay in spec.

• Look for cracks, rubber tearing away from the metal sleeve, and shiny marks where parts have shifted.
• Use a pry bar gently to see if the arm moves more than it should, and compare both sides.
• Sway bar links are a common source of a rattle or clunk over small bumps. Shake the bar or the link by hand. Any free movement means the link needs replacing.

Springs and Ride Height

Inspect for broken coils, cracked leaf springs, shifted leaves and leaking air springs. A vehicle that sits lower on one corner may have a tired spring.

Ride height is the measured distance from a set point on the body or suspension to the ground or another reference point. The service information tells you exactly where to measure. The vehicle should be empty, with the correct tire pressure and on level ground.

Worked Example: Ride Height Check

The spec for a vehicle's front ride height is 14.5 inches, plus or minus 0.5 inch, and the two sides may differ by no more than 0.5 inch. You measure 13.7 inches on the left and 14.4 inches on the right.

The left side is 0.8 inch below spec, which is outside the 14.0 inch minimum. The side-to-side difference is 0.7 inch, which is also too much. Suspect a sagging left spring.

Sagging springs change the vehicle's geometry. Camber, caster and toe all move with ride height, so an alignment on low springs will be wrong, even if the printout looks good. Fix the height first.

Steering System Checks

• Steering wheel free play. With the engine running on power steering, and the wheels straight, turn the wheel gently until the front tires just begin to move. More than about 1 inch at the rim on a typical rack-and-pinion car needs a closer look. The vehicle maker's spec or your state's rule may set a different figure.
• Rack and boots. Check for torn boots, wet leaks and loose mounting bolts. Fluid inside a boot means the rack seal has failed.
• Power steering. Check the fluid level and condition, hoses and the pump. A whine that gets louder when turning suggests low fluid or a failing pump.
• Electric power steering. There is no fluid to check. Scan for faults if the assist drops out, and read the service information.
• Linkage on trucks. Check the pitman arm, idler arm, center link and drag link for play, and the steering shaft joints for looseness.

CV Joints and Driveline Boots

On front-wheel-drive and many all-wheel-drive vehicles, a CV (constant velocity) axle sends power to the wheels while they steer and move up and down. A rubber boot holds the grease in. Check each boot for tears, cracks or splits. A split boot throws grease around the area, then water and dirt get in. Replacing a boot early is much cheaper than replacing an axle. A clicking noise on tight turns usually means a worn outer joint.

Damage From Curbs and Potholes

If a vehicle has hit a curb or pothole, check:

• Wheels for bends and cracks, and tires for bulges and sidewall cuts.
• Control arms, tie rods, knuckles and struts for bends and fresh scrapes.
• Alignment readings, including SAI, once parts pass inspection.

Symptom Guide

Report What You Find

Record what moved, on which side, and how you tested it. Rate each item as safe, needs attention soon, or unsafe. A ball joint with obvious play or a loose tie rod is unsafe. Say so clearly, and do not align the vehicle until it is repaired.

Common Mistakes

Check Your Understanding

1. You feel play with your hands at 3 and 9, but not at 12 and 6. What do you inspect first? Tie rod ends and the steering linkage.
2. You feel play at 12 and 6, and it goes away when a helper holds the brake. What is the likely cause? The wheel bearing. If the play stayed, you would look at a ball joint.
3. A customer hears a clunk when turning the wheel in a parking lot. What do you check? The strut mounts first, then ball joints and tie rods.
4. A front strut is wet with oil, and the tire is cupped. What do you tell the advisor? The strut has failed, and it should be replaced as an axle pair. The cupped tire may also need replacing.
5. The left front corner sits 1 inch lower than the right, and the customer wants an alignment. What is the first step? Measure ride height and fix the spring. An alignment at the wrong height will not be correct.

Key Takeaways

• Rock the tire at 12 and 6 for bearings and ball joints, and at 3 and 9 for tie rods.
• Look at each joint, not only the tire, and use the service procedure for load-carrying joints.
• An oily film means a damper is leaking. The bounce test is only a rough check.
• Worn mounts and links often cause clunks.
• Ride height affects every alignment angle.
• Repair loose parts before any alignment, and report safety items clearly.