[Funlovincriminals]

Hi all👋help me solve the problem

BMW M5 F90 Competition 2021

When passing speed bumps in the rear of the car, a loud sound is generated, accompanied by a kickback on the body. It feels like a loose object that, when driving over an uneven surface in the compression/distension phase of the suspension, jumps up and drops sharply. It does not depend on the ambient temperature, vehicle loading, luggage compartment, fuel tank fullness or other factors. It appears consistently from the moment I started using the vehicle.
If I pass a speed bump quickly or, conversely, too slowly, the sound does not appear. When driving in the usual mode, accentuated subsidence and return of the rear axle always appears.

It doesn't feel like a suspension problem, but like a loose object in the car.

We have been dealing with this problem at the official dealer for two months now, but we cannot find the cause.

⁃ The luggage compartment of the car, the rear shelf, and the rear seat were completely disassembled
⁃ They took off the bumper
⁃ Complete chassis diagnostics
⁃ A speed bump was installed in the workshop. The sound appears, but its localization cannot be determined from the outside
⁃ The technicians rode in the trunk, in the rear cabin without a seat, the unit is also not clear
⁃ Checked the brake pads
⁃ Just in case, we changed the rear shock absorbers
⁃ Replaced the fuel tank according to TIS BMW with reinstallation of many components, including the exhaust route

all this did not lead to results.

and, most importantly, I drove other m5 f90 competition and they also have this effect. what is this?)) please tell me, share your experience.
Thanks🤝

[kbright1892]

Mine does this, too. I notice it most in my neighborhood when in hit some small uneven areas/transitions at speeds around 25-35mph. I don’t hear it as much at lower or higher speeds on other roads. Indiana roads aren’t great, and some in my neighborhood are a little worse for wear. However, I have a Dinan HAS on mine, so I just figured it was tapping the bump stops, even though I have it lowered as little as possible. I’ve checked things like making sure the battery is locked down tight. I just deal with it now.

[Funlovincriminals]

Originally Posted by kbright1892

Mine does this, too. I notice it most in my neighborhood when in hit some small uneven areas/transitions at speeds around 25-35mph. I don’t hear it as much at lower or higher speeds on other roads. Indiana roads aren’t great, and some in my neighborhood are a little worse for wear. However, I have a Dinan HAS on mine, so I just figured it was tapping the bump stops, even though I have it lowered as little as possible. I’ve checked things like making sure the battery is locked down tight. I just deal with it now.

Yes, guys who have good roads in the area may not notice this at all. but in my area after leaving home there are dozens of speed bumps. and there are a lot of them in the city. I immediately checked such things as the battery mount and other little things. This is something deeply hidden in the car, most likely under it. This noise and knocking cannot be called an obvious malfunction. but it seems that some object is out of place and is bouncing. I keep searching)

[Danny D]

could it be the tire inflator kit hidden in the truck on drivers side - maybe take it out of the car and see if that helps.

[nordmanmg]

Can it be a derby or a piece of a rock somewhere in a rocker panel or on top of a fuel tank or inside of a subframe tube?
Or on top of a plastic undercarriage covers

[Funlovincriminals]

Originally Posted by nordmanmg

Can it be a derby or a piece of a rock somewhere in a rocker panel or on top of a fuel tank or inside of a subframe tube?
Or on top of a plastic undercarriage covers

no, of course we checked such moments immediately. Everything was taken apart and looked at. it's something in the body of the car

[nordmanmg]

Originally Posted by Funlovincriminals

no, of course we checked such moments immediately. Everything was taken apart and looked at. it's something in the body of the car

how about coil springs? i had lowering springs on another car and one of the springs cracked about half a coil and was clicking in the left rear. took me a while to see it and replace it. it was not noticeable at all,
Another guess would be faulty strut.