Check your springs!!
 

So a week or so ago I reversed off the drive, full lock only to be greeted with a loud metallic 'boing' noise! Knew instantly the spring had snapped.

Ordered a replacement pair (H&R) and had it in the garage today for fitting.

Turned out BOTH the front springs were broken, one fresh (last week), the other clearly some time ago.

The car drove perfectly, only making any noises after the second spring broke last week. I've had broken springs on several bmws in the past, it seems not even the mighty X5 is immune!

Might be worth checking yours? My car has 124k miles and only went through an mot some 7 weeks ago!

Thanks for the heads up!!! The Z4 is notorious for snapping rear springs

http://i147.photobucket.com/albums/r...gAlpina001.jpg

Amazing! I have always been taught, and taught to others, that springs are among the most reliable of engineered structures.

At a glance, that illustrated spring failed for contact between the coil and the seat-coil.

This may be informative: Engineering Failure Analysis 15 (2008) 1155–1174
Design and Failure Modes of Automotive Suspension Springs

http://www.scribd.com/doc/27577332/D...ension-Springs

I'm wondering if the fact that the springs are progressive has anything to do with it in particular since the progressiveness is achieved by changing the section of the spring: thoughts?

As long as section changes smoothly then there are no stress risers or concentrators.

As noted in the article, flaws internal and external, perhaps due to corrosion are common sources of failure - stress concentrators.

As above, I believe that it was contact with the seat coil that added to the expected stress and strain..

Yes I should add that the springs were broken just past the first coil, not smack in the middle