BMW Z4 Rear Suspension Issues Explained(+3Tips)

In this brief article we are going to discuss the rear suspension issues that occur in the BMW Z4, what causes these failures and some troubleshooting tips.

The Top 3 Most Common problems with BMW Z4 Rear Suspension are:

  • Rear Shock Absorber Failure
  • Rear Squeaking Noise
  • Rear Trailing Arm Bushing Failure

BMW Z4 Suspension

The BMW Z4 is the third model in succession within the BMW Z Series. The Z4 is the successor to the outgoing Z3 and is based on the E85/E86 platform.

The Z4 front suspension is carried over from the E30 3-series models. It is a MacPherson Strut suspension with an Anti-Roll Bar.

The  “Z-link” rear suspension is common with the E46 (3 series) cars. This arrangement has a large semi-trailing arm, an upper link and a lower link per side. 

Troubleshooting problems with BMW Z4 Suspension

Rear Shock absorber Failure

Symptoms:

  • Poor handling especially during slightly fast cornering
  • Rear end feels less stable
  • Knocking and Squeaking noises
  • Bouncy rear end going over bumps
  • Rear wheels feel ‘floaty’ going over rough patches

Troubleshooting Rear Shock absorber Failure

  • Handling problems usually point to a problem in lateral grip. Now this could be either the tires or the Rear Shocks.
  • It seems that the inside wheel was not planted enough on the tarmac to get lateral grip.
  • Going over rough surfaces, the damper’s job is to keep the tires planted on the road surface. The ‘Floaty’ feeling is clearly due to a lack of Damping at the outside corner while cornering.
  • Squeaks and Knocks are also typical symptoms of Shock Absorber failure
  • Once the Tire is ruled out as a potential cause, then the only remaining Root Cause is the Rear Shock absorber. Weak/Leaking Shock Absorbers can cause lateral grip problems.
  • Check the condition of the shock absorbers’ upper and lower mounts
  • Also check for oil leakage stains on the shock tube
  • Even if there are no oil stains, the shock could have simply worn out over the miles. Typically the shocks would last around 40K miles depending on usage. It is recommended to replace at 50K miles, when you would most likely see deterioration in performance
  • While replacing the shock, make sure to replace the rubber mounts and bump stops as well.

Rear Squeaking Noise

Symptoms:

  • The Rear squeaking happens when going slowly and climbing a carpark ramp
  • Otherwise no noise issue while going over bumps

Troubleshooting Rear Squeaking Noise

  • In order to identify where exactly the squeak is coming from, you can simulate the rear suspension movement and closely observe the squeak closely
  • For this, lift your rear body and place it on Jack-stands
  • Now use a hydraulic jack to lift and lower the rear wheel hub to simulate suspension movement
  • Move the rear wheel carrier up and down a few times and listen closely for the source of the squeak noise.
  • If needed, you can use a long shaft Screwdriver and place the handle at your ear while the tip is at various suspension mounting points.
  • Lower Control  arms are known to squeak from past experience
  • If the bushing is still intact and in working condition, you can try a “Quick-Fix” solution to eliminate the noise problem
  • Use a Pointed tool to poke holes into the exposed Rubber Portion of the Bush
  • Spray WD 40 into the new bushing holes using a nozzle
  • Once again, using the Hydraulic Jack, move the rear wheel carrier up and down in order to let the lubricant spread throughout the joint.
  • Lower the vehicle and see if the problem has been eliminated in normal driving

Rear Trailing Arm Bushing Failure

Symptoms:

  • Uneven Rear Tire Wear
  • Poor Handling especially during a lane change
  • Rear end rolls excessively
  • Rear Knocking noises driving over rough surfaces and Bumps

Troubleshooting Rear Trailing Arm Bushing Failure

  • Given the Z4’ rear Trailing arm type of suspension, the Rear roll stiffness of the Z4 is influenced in part by the trailing arm Bushes.
  • Failed rear control arm bushes do contribute to the handling feel
  • The Rear Wheel Hub is attached to the Trailing Arm and therefore the Toe-setting of the rear wheels are influenced by the trailing arm Bushing. This is evident in the Tyre wear issue.
  • The trailing arm bush can be replaced using a Service Kit that can be purchased
  • You could also get a puller clamp to remove and fit the bush

And also avoid removing the entire trailing arm as well

Rear Lower Control Arm Bushing Failure

Symptoms:

  • Uneven Rear Tire Wear
  • Poor Handling; Rear end rolls excessively
  • Rear Knocking noises driving over rough surfaces and Bumps

Troubleshooting Rear Lower Control Arm Bushing

  • The ‘Camber’ setting of the rear Wheels is influenced by the Lower COntrol Arm bushings.
  • If the Lower Control arm bushings have worn out, the rear wheels go out of alignment, resulting in Uneven Tire wear
  • The Lower Control Arm bushings also resist lateral movement of the Tires.
  • Failed bushings would allow excessive lateral movement of the tires and adversely affect handling of the vehicle.
  • It would be best to replace the Lower Control arms along with the bushings

Conclusion

In this brief article we have discussed the rear suspension issues that occur in the BMW Z4, what causes these failures and some troubleshooting tips.

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