Hyperco Transfer Assist Springs are special tuning springs used in Midget Sprint and Micro Sprint racing.  With a free length of 4in, an ID of 1.875” and rates of 25lb/in and 50lb/in; these springs are used in series with the main springs in the suspension.  They offer much of the same function of a Helper Spring, but have a higher rate to provide some tuning of the suspension to improve roll control.  They are designed in an under-stressed condition because they spend much of their operating life at coil bind.