Composite leaf springs constructed of glass fiber reinforced polymeric material have been recognized as a viable replacement for steel leaf springs since their introduction on the 1981 General Motors Corvette. This acceptance of composite leaf springs has given rise to applications in high volume production passenger cars and vans. The increased reliability and utility of composite leaf springs is clearly demonstrated in these applications.This paper will discuss the design, laboratory testing, field testing, and development over the past three years that has led to the commercialization of the Liteflex trailer spring. This will include the design process for high and low deflection composite leaf springs and the stress analysis for common springs used in various axle spacings worldwide. An explanation of laboratory tests will be given and the rationalization for these tests compared to current steel spring test standards. An attempt will be made to correlate laboratory, test track, servo-hydraulic simulator, and field tests of Liteflex trailer springs. This testing will demonstrate the soft failure mode of the composite leaf spring and the advantage this brings to fleet owners. The other advantages of weight reduction and increased durability will be discussed.In conclusion, the paper will discuss the design limits imposed by fitment of the Liteflex composite spring into existing suspension hardware and suggestions for future suspension modifications to better utilize the advantages the Liteflex composite spring brings to truck trailer applications.