Offers increased clutch capacity. Reduces clutch slippage and resultant heat build-up under heavy use. Stage III for 98 cu. in.: The spring rate is about 7% stiffer than the stock spring for 98 cu. in. engine to handle the increased power output from Stage III configuration. Stage IV for 98 & 102 cu. in.: The spring rate is about 25% stiffer than the stock spring to handle the increased power output from Stage IV configuration. SPD-5PX09-84-00: The spring rate is 20% stiffer than the stock spring for increased clutch capacity. Reduces clutch slippage and resultant heat build-up under heavy use. Designed to handle increased power output from Stage IV configuration.