2018-2020 BMW M5 (F90) Rear Suspension: Diagnosing Clunks, Bushing Wear, and Competition Package Differences

Symptoms of a Failing Rear Suspension Assembly

Failures in the F90 M5's rear suspension assembly typically relate to the wear of its many rubber bushings, rather than catastrophic failure of the metal components. These symptoms often develop gradually. Forum users frequently report clunking sounds from the rear as the first sign of trouble.

• Clunking or Knocking Noises: The most common symptom is a distinct clunk, pop, or knock from the rear of the car, especially when driving over bumps, uneven pavement, or during acceleration and braking. This sound is caused by worn bushings allowing metal components to make contact.
• Unstable or Loose Handling: The rear of the car may feel 'loose' or disconnected from the chassis, particularly during lane changes or cornering. This feeling of instability is a sign that the suspension components are shifting unpredictably.
• Uneven Tire Wear: When bushings fail, the precise alignment of the rear wheels is compromised. This can lead to accelerated wear on the inside or outside edges of the rear tires, even if the car has recently had an alignment.
• Excessive Vibration: Worn subframe or control arm bushings can no longer effectively dampen vibrations from the road, which may be felt in the cabin.

Known Issues, TSBs, and Recalls

As of this writing, there are no major recalls from the National Highway Traffic Safety Administration (NHTSA) for the rear subframe, control arms, or suspension assembly on the 2018-2020 BMW M5. Recalls for this period primarily concern the rearview camera and transmission wiring harness.

However, BMW did issue a relevant Technical Service Bulletin (TSB):

• TSB B330319 (December 2019): Titled "SERVICE ACTION: CHECKING THE THRUST WASHER AND THE REAR AXLE ANTI-ROLL BAR." This bulletin addresses a potential issue where an incorrect setting could cause the thrust washer to contact the anti-roll bar (sway bar) over time, which could be a source of noise.

Base vs. Competition Package: Critical Differences

It is absolutely essential to know whether your M5 has the Competition Package before sourcing a used rear suspension assembly. While they look similar, there are significant differences in the suspension tuning that make the assemblies incompatible.

• Stiffer Components: The Competition package features stiffer springs (approximately 10% stiffer), firmer dampers (shocks), more rigid engine mounts, and potentially different anti-roll bars and control arm bushings to provide a more track-focused feel.
• Ride Quality: The result is a much firmer ride, which many drivers have noted as being harsh on poor road surfaces, especially on pre-LCI (2018-2020) models.
• Verification: Do not mix and match parts between Base and Competition models. Verify the package on your vehicle and the donor vehicle before purchase. Using a Competition assembly on a Base car (or vice-versa) will negatively affect handling, ride height, and electronic stability control systems.

Buying a Used 2018-2020 M5 Rear Suspension Assembly: A Step-by-Step Inspection Guide

A complete, low-mileage used rear suspension assembly can be a cost-effective solution, saving significant labor compared to replacing multiple individual bushings and control arms. Here’s what to inspect.

Physical Inspection Checklist

• Subframe Integrity: Carefully inspect the entire subframe for cracks, especially around the welds and mounting points where it attaches to the car body. Check for any signs of distortion or impact damage.
• Control Arms: Look down the length of each control arm to ensure it is perfectly straight. Any bend, no matter how slight, means the part is compromised and must be replaced.
• Bushings: This is the most critical inspection point. Check every rubber bushing for signs of tearing, cracking, or deterioration. Some bushings are fluid-filled; any sign of leakage means the bushing has failed. Worn bushings are the primary reason for replacing the assembly, so an otherwise good assembly with bad bushings is a poor value.
• Hubs and Bearings: If the assembly includes the wheel carriers (knuckles), check them for any cracks or impact marks. Spin the wheel hub by hand; it should rotate smoothly and silently. Any grinding noise or side-to-side play indicates a bad wheel bearing.
• Origin: Whenever possible, choose an assembly from a vehicle with no reported accident history. Look for deep scrapes on the bottom of the subframe or control arms, which could indicate the donor car was dragged after a collision.

Replacement and Installation

Post-Installation Requirements

After the new assembly is installed, a professional four-wheel alignment is mandatory. Failure to perform an alignment will result in poor handling and rapid tire wear. The shop should also check for any required calibrations related to the electronic stability control (DSC) and active differential systems.

Cost of Replacement: 2018-2020 BMW M5 Rear Suspension

Prices can vary based on location and the specific components being replaced. A complete assembly is often more economical than replacing parts individually due to high labor costs.

OEM Part Numbers

This list contains known OEM part numbers for major components of the rear suspension assembly. Always verify the exact part number for your specific vehicle and package (Base vs. Competition) using your VIN.

• Rear Axle Carrier / Subframe: 33316886057
• Wheel Carrier / Knuckle: 33308091698
• Rear Lower Forward Control Arm: 33328091698
• Other Control Arms: 33308064893, 33308091482, 33308091483, 33309503995, 33309503996
• Stabilizer Bar / Anti-Roll Bar related: 33507856901, 33507856904

Frequently Asked Questions (FAQ)