'Ballast' weights inside rear bumper corners

[Paul Weller]

Hi
Does anyone know the design intent of the massive cast iron weights hidden inside the rear bumper corners? I would guess they are about 10kg per side.

Could it be:-

To reduce scuttle shake?

Part of the shock absorption crash protection?

BMW marketing wanting to improve the weight distribution?

Acceleration would certainly be quicker without them!

 

[the Nefyn cat]

Pretty sure these have been mentioned before on here, some kind of vibration damper seems to be the conclusion. There used to be a weight on my silencer, took it off a while ago as it had unbonded itself and doesn't seem to have made any difference.

 

[Paul Weller]

Pretty sure these have been mentioned before on here, some kind of vibration damper seems to be the conclusion. There used to be a weight on my silencer, took it off a while ago as it had unbonded itself and doesn't seem to have made any difference.

Suspect it has a greater importance on the bigger engine/ heavier models and less on the basic ones.

 

[the Nefyn cat]

Perhaps they're just too fussy. Having heard something on Radio 4 a while back about some sound lab that " a premium German car manufacturer" was using to make the doors make the right sound as they were closed I feel they just might be too damn fussy at times. May be wrong, I have been at times.

 

[Sean d]

They are indeed vibration dampers and I don't believe BMW would have gone to the trouble and expense had they not been needed.

 

[Stevo7682]

I'm with Sean on this if they weren't needed they would not be there .
Even the very newest 3 series still have a version of these in the rear and have various rubber dampers on diffs and exhausts.
Also the fact that these are mounted right at the rear will give more pivotal load than a heavier weight more centrally mounted.

 

[Paul Weller]

They are indeed vibration dampers and I don't believe BMW would have gone to the trouble and expense had they not been needed.

I guessed as much. However you could extend your response to '' they wouldn't........springs and dampers........ So by the time everyone has done their own thing in these the vibration/ frequency dampers will have well and truly missed their sweet spot, so might as well be taken off anyway??!

 

[Sean d]

I guessed as much. However you could extend your response to '' they wouldn't........springs and dampers........ So by the time everyone has done their own thing in these the vibration/ frequency dampers will have well and truly missed their sweet spot, so might as well be taken off anyway??!

It often makes me laugh when I see peeps trying to take weight off the car as most of them are about 5 stone overweight

 

[gookah]

scuttle shake dampeners...
they are not fitted to the coupe...

 

[Dino D]

scuttle shake dampeners...
they are not fitted to the coupe...

And they do sweet f’all about the shaking about lol.
They should have spent more time making it more rigid in the first place!

Anyway at least it has the accolade of most flexible German car ever made. Adds character to handling, after all anyone can drive a stiff chassis fast (all you coupe boys )but it needs real skill to get roaster round a bend

 

[gookah]

it needs real skill to get roaster round a bend

Agreed. My missus can get the potatoes out of the oven, and around a sharp corner to the dining table without dropping them.....

 

[5harp3y]

And they do sweet f’all about the shaking about lol.
They should have spent more time making it more rigid in the first place!

Anyway at least it has the accolade of most flexible German car ever made. Adds character to handling, after all anyone can drive a stiff chassis fast (all you coupe boys )but it needs real skill to get roaster round a bend

Go drive a mk1 golf convertible .

 

[Dino D]

Go drive a mk1 golf convertible .

Really, even with the massive bar in the middle, guess it was ancient design and very lightweight in the first place....Probably more rigid than this though. Made the Z3 feel like an F1 car!

 

[littlefeller]

It often makes me laugh when I see peeps trying to take weight off the car as most of them are about 5 stone overweight

There was a post a few years ago on another forum where some chap was asking questions on weight loss as he had a large passenger, I suggested the cheapest option was to dump the passenger and he replied sorry fat ar**as and big ti*s is how I roll.

 

[5harp3y]

Really, even with the massive bar in the middle, guess it was ancient design and very lightweight in the first place....Probably more rigid than this though. Made the Z3 feel like an F1 car!
View attachment 82518

Super floppy compared to the z3

 

[Sean d]

Super floppy compared to the z3

I thought my 2.0l went around corners like it was on rails until I had @billz behind me on a run in his Z4, I was getting out of shape all over the place and pulled over to let him and @MAURICE THE MARTIAN pass me

 

[Paul Weller]

Agreed. My missus can get the potatoes out of the oven, and around a sharp corner to the dining table without dropping them.....

Does she have a pair of mass dampers though?

 

[the Nefyn cat]

Really, even with the massive bar in the middle, guess it was ancient design and very lightweight in the first place....Probably more rigid than this though. Made the Z3 feel like an F1 car!
View attachment 82518

Hmmm. Them blokes off Top Gear been in town, perhaps?

Not suggesting that the weights aren't needed, just that the one on my cars' silencer had come un-bonded so I took it off after four years, and there doesn't seem to be any difference. No better, no worse. Just a few ounces lighter, which makes all the difference with a 2.2.