Spring rates refer to the measure of how much a spring compresses or extends under a given load. It is typically expressed in units like pounds per inch (lb/in) or Newtons per millimeter (N/mm). A higher spring rate means the spring is stiffer and requires more force to compress, while a lower spring rate indicates a softer spring that compresses more easily. In automotive applications, spring rates play a crucial role in determining ride quality and handling. For instance, coil springs in a vehicle's suspension system must be carefully selected to balance comfort and performance, ensuring that the vehicle responds well to road conditions while providing a smooth ride.