The design of helical coil springs with variable coil diameters is attractive for its ability to reduce packaging requirements. The reduction of end coils can be achieved by spring shape like double cone or barrel. But the development of such springs has been limited by their large additional cost compared with cylindrical coil springs.A new process of production by cold coiling of wire pre-hardened by quenching and tempering has now proven its ability to meet automotive performance requirements and is now used on large scale in Europe. This process allows complete design freedom without additional cost.Design variables for barrel springs produced by this new process are presented for both constant and for variable rate springs. Capability data are derived from laboratory tests on numerous lots of springs. Cost information is likewise given.