According to the annual Infrastructure Report Card by the local ASCE, the rating for road quality is a D+. In fact, since 2000, it has mostly remained at a D level.

Chassis parts of vehicles naturally experience wear and tear. According to research and sales data from the T.G.Q, the lifespan of chassis parts for Japanese cars is approximately 90,000 miles. On the contrary, European and US cars last around 80,000 miles. However, due to the poor road conditions in the US, many vehicles may begin to show chassis deterioration symptoms as early as 65,000 miles.

Within the chassis, all parts are susceptible to damage. The symptoms caused by such damage can vary or sometimes appear similar. In this article, T.G.Q will try to list the possible causes behind bad suspension, hoping to provide some helpful insights.

1. Tie Rod and Tie Rod End

  • When the vehicle is lifted, the wheels can be easily wobbled by hand.
  • The vehicle cannot maintain proper toe alignment, making it difficult to drive straight and requiring constant steering correction.
  • Abnormal tire wear.
  • A rattling sound occurs when turning the steering wheel.
  • When only one wheel hits a pothole or uneven surface, the steering wheel vibrates and is pulled to one side.
  • Vague steering response and increased play around the center position. You may turn the steering wheel, but the car doesn’t respond immediately. This issue is harder to notice, as it develops gradually over time rather than happening all at once.

2. Steering Gearbox

  • Extra effort is required to turn the steering wheel, especially at low speeds or when turning the wheel while stationary.
  • Whining, grinding, or knocking noises may occur when steering.
  • Steering feels vague or loose when turning, with a noticeable lack of precision.
  • Play or movement in the steering linkage can be felt inside the cabin.

3. Ball Joints

  • Clunking or knocking noises, especially near the wheels, most noticeable when the tires move up and down (e.g., over bumps or potholes).
  • Wandering steering – the vehicle may drift or feel unstable, as worn ball joints can lead to vague or imprecise steering response.
  • Loose or unstable chassis feel, often subtle and hard to notice at first, as the issue tends to develop gradually over time.
  • Difficulty with wheel alignment – worn ball joints can prevent accurate alignment, affecting drivability and tire wear.

4. Strut Bearing

  1. Steering feels stiff or jerky at low speeds, especially when turning the steering wheel.
  2. Squeaking or clicking noises from the front wheels during turns.
  3. Slow steering wheel return.
  4. Inspection requires removing the upper strut assembly. When replacing this part, it is recommended to replace the entire strut top mount to avoid doing the job twice. When damaged, the entire bearing structure is compromised, and sometimes even the ball bearings inside are missing, making it easy to identify.

5. Strut Mount Rubber

  • Clicking or cracking sounds can occur during cornering or compression.
  • Uneven ride height, possibly caused by one side’s rubber cushion deteriorating over time.
  • This can lead to complete failure of the upper mount, which will prevent the shock absorber from functioning properly.
  • When replacing this part, it is recommended to replace the entire strut top mount to avoid doing the job twice.
  • Steering may make abnormal noises or a shaking feeling.

6. Stabilizer Bushing

When driving over speed bumps, a creaking noise may occur, which could indicate worn stabilizer bushings. Perform a visual inspection for obvious cracks; if found, replacement is necessary. If no cracks are visible, applying some lubricant may help reduce the noise. However, since stabilizer bushings are usually located in the middle section of the vehicle’s chassis, it is generally not recommended to inspect them by yourself.

7. Stabilizer link ball joints

When the vehicle passes over speed bumps, a clunking noise may occur. This could indicate damage to the stabilizer link ball joints. However, the stabilizer link ball joint cannot be replaced individually and must be replaced as a whole unit. Additionally, if budget allows, it is advisable to replace both the left and right sides together.

Sometime, inexperienced technicians may install the stabilizer bar incorrectly, causing suspension noise. This situation is particularly troublesome because the noise appears after the replacement, and technicians often do not suspect the newly replaced parts as the cause.

8.Control Arm Bushing

  1. Although most of the vehicle’s vibrations are absorbed by the shock absorbers, a small portion is handled by the control arm bushings. Prolonged exposure to high temperatures, high humidity, or salty environments can shorten the lifespan of these bushings.
  2. The vehicle may experience a nodding motion or front-end sway during braking.
  3. When driving on rough roads, you might hear metallic knocking sounds coming from the chassis. Compared to the noises from the shock absorbers, these sounds tend to be sharper and more frequent.
  4. Wheel alignment may become inaccurate.
  5. During inspection, damaged bushings are usually easy to identify due to visible wear or cracks.
  6. In countries with relatively low labor costs, replacing bushings alone is a common practice. Whether this is possible depends on the design of the control arm.

9. Shock Absorber

  • Oil leakage
  • Increased body sway or oscillation, especially noticeable during cornering, causing a feeling of severe body roll and reducing driver confidence
  • Increased bumpiness and harshness while driving
  • Abnormal tire wear
  • Knocking or rattling noises

Conclusion

There are many sources of abnormal noises coming from underneath a vehicle, including drivetrain components not covered in this article. However, when it comes to steering and suspension systems, issues other than noises are usually difficult to detect. Therefore, the first step is to check for any unusual sounds. Then, inspect the parts listed in this article by physically shaking them or visually checking for visible damage. This basic approach can generally help determine whether a specific component is broken.

Reference

T.G.Q R&D

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Components of the Suspension System: What Are Their Functions?
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Older What Do Stabilizer Bars Do? How They Reduce Body Roll in Turns?