What goes wrong with Coil Springs?

Coil Springs have a tendency to sag over time, however breakage has become more common in the last 15 years.
If this happens it is a serious fault and needs addressing urgently, it can also have devastating consequences – on some cars, the broken section of the coil spring can pierce the tyre sidewall, increasing the chances of the driver losing control.
Coil Spring breakage has been blamed on the materials the springs are made of, they are lightweight and often have a high recycled metal content. Poor design, increased forces and bad road quality have been listed as other contributing factors, but none of these have solely been confirmed as the cause.
Coil Springs must be replaced in axle pairs, to reduce the chance of an imbalance and care must be taken during removal to ensure that any part of the broken coil spring doesn’t fly off the suspension and cause injury.
Manufacturers are becoming more aware of the ongoing issues surrounding springs and started to introduce some new materials to the market for some models. Audi introduced a glassfibre reinforced plastic coil spring in 2014.
So there is hope that in time manufacturers may be able to improve the longevity of these parts.