clanging noise from drivers rear suspension

[Adam D]

Hmm have those all also had to have the spring replaced needed a alignment check done, BMW charge a fortune for that.

Springs shouldn't go twang though, who are they made by?

 

[Curtis]

Wondermike

Your quite right. Coil springs through time will start to sag and loose their "memory" in other words they will start to loose their ability to return to their original length or shape. This is quite natural, it's the same thing that happens to the springs in your mattress. Over time they will start to sag or dip in the areas that get most use. ( I'm sure someone will think of a smutty remark regarding this!)

The problem however is this and it may be more apparent to those of you who have ever fitted coilovers. The adjustable platforms on coilovers are designed primarily so that you can adjust the cornerweight of the car, in other words you can dictate the percentage of the cars total weight that is over each corner ie pressing down on each tyre. In racing this is crucial for adjusting the handling characteristics of the car both from side to side and front to rear. OEM suspension is non adjustable and the cornerweight is predetermined by BMW. It's not very good by the way, 50/50 weight distribution my ass!

If you were to replace one rear coil spring and keep the other worn and "dipping" spring you will effect the original cornerweighting and the car will have different handling characteristics between left and right hand turns, it can also have an effect on braking because their can be a dramatically different weight pressing down on each of the rear tyres which can cause one brake to prematurely lock under heavy breaking. There are other symptoms other than these examples but I'm sure you get the picture.

Long story short, replace both springs at the same time so you don't loose the symetry and balance.

Adam D

There should be no reason to have your alignment checked after spring replacement however it is always good to check your settings have not gone out of tolerence from time to time simply from bumps and knocks during day to day driving. It is more likely that replacing the springs will return the alignment settings to their original position (assuming the alignment hasn't been compromised due to some other incident). The geometry is more likely to wander out of spec as the old springs wear and start to sag.

 

[Screamer]

im hearing some noise from the rear(metal to metal) but very randomly but constantly comes back. My car doesn't seem to have handling issue and I checked the springs(shook em around while the wheel was off) and it was pretty firm

Hi BSZ - does yours seem linked to the rotation of the car's wheel? I've got a funny metal scraping sound coming from the right-rear of mine at the moment, and like yours, it comes and goes. Did it all the way back from a cinema trip recently, so I was planning on getting some to have a good listen while I rolled the car forwards slowly... Unfortunately, I turned 90 degrees right 1 turn from the entrance to our street and the sound stopped, so i'm still unsure of what's causing it. Apparently clips on the brake calipers can go (on all cars), and it might well just be one that's come loose but hasn't pinged completely away..? I'm off to the Nurburgring at the end of Sept, so i'm gonna have to see if I can get the noise back and have a look myself/get it to a dealer asap. I'll definately be having a look at the springs, although I can't imagine how they'd cause this sorta sound...