Knocking sound over uneven surfaces

[Rockhopper]

Ah, fair enough.

[john-e89]

Wrong spring in the damper won’t be good..looks like you have an MSport spring one side and non MSport other side ..or damper body..or broken spring ..

Others have had issues with incorrectly supplied springs causing much confusion

There's only 10mm difference between M sport and standard height springs though right...?

Correct ..however the dampers are also different between MSport and ‘normal’..

One member here had a MSport spring inadvertently supplied instead of a stock ride height spring and the effect was very obvious visually and ride height wise..

Also springs sag with age and use which compounds any differences…

As I said could be many other factors too..

Yes but dampers have no effect on ride height, that's down to springs.

[Pondrew]

Yes but dampers have no effect on ride height, that's down to springs.

And weight of the occupant(s)

[B21]

The dampers may affect the ride height for at least two reasons…

The sports damper has a shorter stroke..so the maximum possible extension / compression is more limited..

Depending on where the spring is attached to the bottom pre load collar the spring rate of an incorrect spring may affect both preload and therefore ride height..

I’m not sure that both dampers have their bottom collars in exactly the same position relative to the bottom mount?

[john-e89]

If you fit a damper for an E89, beit M sport, standard, Ohlins, KW's etc, they have no influence on ride height. If I wind my KW's up to full hardness it doesn't jack the back of the car up to look like a dragster, same for if I set them to fill softness, it doesn't squat on the ground scraping the exhaust. It's stays the same height.

[B21]

If you fit a damper for an E89, beit M sport, standard, Ohlins, KW's etc, they have no influence on ride height. If I wind my KW's up to full hardness it doesn't jack the back of the car up to look like a dragster, same for if I set them to fill softness, it doesn't squat on the ground scraping the exhaust. It's stays the same height.

That maybe so on some of those dampers but not Ohlins R+T you can adjust the static ride height by at least 40mm if you so wish..

Ohlins suggests a ride height analogous to MSport ride height but you can vary it by quite a large amount.

I’ve changed them on mine by about 30mm at various times to see what effect they have on ride and handlimg.

https://world.ohlins.com/app/uploads/20 ... MSMP50.pdf

Refers

So in the case of Ohlins they pitch the nose down by 5mm compared to a stock MSport setting.

[javis20]

I had this problem and it was finally solved today. Local BMW indie mechanic found that the rear sway bar shifted to one side and came out of the bushing. Don't know how or why, but he put everything back into position and it's clunk free now.

[warmasice]

Check your rear anti-roll bar links. Especially if you replaced the rear springs without disengaging the hand brake.

Are you sure the noise isn't coming from the rear roof clamshell hitting the rear deck. It should sit around 3mm off the black boomerang bit that sits on the top of the boot lid.

[stannie203]

That's not a bad shout re the clam shell. When the weather has been cold and the car has a layer of frost on it I get a really distinctive noise coming from back there, as if it's creaking/scratching and breaking the ice as the shell moves.

And looking at the shell where it meets the rear of the car, there are two blobs (as if the paint has dropped and set) on either corner which takes that part of the shell much closer to the rear shelf. Could be that those are hitting?

Is there a way to adjust this gap to 3mm? But in doing so, is there a danger that the seal won't meet and water will get in?

[javis20]

I had the knocking sound. Turned out to be the rear sway bar slipped to the side and out of the right side bushing.