Suspension Confusion

[Craig-SM]

The rear off side is sagging by around an inch compared to the others. I noticed this as the wife was about to go to work in it. Stopping her thinking it was a broken coil, I then took her to work in my car so i could inspect hers later.
Jacked up, wheel off and there is nothing wrong with the coil or the shock. No worn bushes or bent arms, taking it for a spin and no unwanted bangs or scraping. Now confused as to what it could be. Any suggestions?

Background: 2013 F30 320D M Sport, around 66K miles and original suspension

 

[mr haynes]

Couple bags sand in boot on that side?

 

[Ashley Burton]

Collapsed top mount?

 

[mr haynes]

What measurements did you take?
Arch to ground
Compressed coil length etc

 

[stuvy]

Collapsed top mount?

that’s where I would look

 

[Craig-SM]

Nothing of any weight in the boot.

The coil just sits in a cup at the top of the subframe and the bottom on the lower arm. All rubber springs caps are there and no broken ends of the coil.

The measurement is taken from the tyre to the arch on level ground

 

[Rannsachair]

Nothing of any weight in the boot.

The coil just sits in a cup at the top of the subframe and the bottom on the lower arm. All rubber springs caps are there and no broken ends of the coil.

The measurement is taken from the tyre to the arch on level ground

Sounds like a new spring is needed as one has sagged then, I always used to replace pairs of springs per axle, though not sure if that is still the normal practice.

 

[mr haynes]

If mountings are fine i would compare the spring length both sides.
As said above that spring may well just be more tired.

Not lost the end off the spring has it? Edit: Already answered that one

 

[Craig-SM]

Cheers, I've never had a spring sag on just one corner before as they've normally just snapped on other cars.

I'm also replace both sides as I don't see the point in just doing one side. I may as well replace the shocks whilst I'm at

 

[Ashley Burton]

@Craig-SM If your going the full distance, Then I would do the top mounts also!

Can't remember which BMW has it, But one of them has also has a bottom mount on the shock which bolts to the suspension which seems to fail

 

[Craig-SM]

Only the front has top mounts on the BMW F30, the rear spring is just compressed in rubber cups between the subframe and lower arm

 

[Ashley Burton]

@Craig-SM I'm with you!

Is your m sport lowered suspension do you know?

 

[stuvy]

@Craig-SM If your going the full distance, Then I would do the top mounts also!

Can't remember which BMW has it, But one of them has also has a bottom mount on the shock which bolts to the suspension which seems to fail

e46 has that issue

 

[Craig-SM]

No, just the standard M Sport suspension - non adaptive

 

[minimutly]

Now then - is it down at the front or rear? If its the rear have a long hard look at the top arm, been known to suffer from corrosion, semi collapse.
Rover made copies from steel, known to totally collapse.

 

[Ashley Burton]

e46 has that issue

It was a later model, Possibly E60 maybe it was an E60/61

They're all BMW to me!

 

[colnerov]

Sounds like a new spring is needed as one has sagged then

Especially if it's driven solo most of the time, other people of a different weight are also available.

 

[Craig-SM]

Especially if it's driven solo most of the time, other people of a different weight are also available.

Are you saying my wife is fat

If it was me driving it then you'd be spot on

 

[brightspark]

Sounds like a new spring is needed as one has sagged then, I always used to replace pairs of springs per axle, though not sure if that is still the normal practice.

its preferable yes
if ones worn and one isn't going over bumps will make the car chassis twist

 

[stuvy]

its preferable yes
if ones worn and one isn't going over bumps will make the car chassis twist

This happens on m3’s