well air bags is one way . and can just buy the rear set from most places. if thats toomuch then try buying a set of air shocks from your local auto parts store . you can air then up with a bike pump if need be but an aircompressor is best .and you can deflate them too therfor softing the ride . if all els fails swap out the leif springs for a set of coil springs . if you know how to weld thatd make it alot cheeper .How do you improve mini truck ride quality?
Lower the tire pressure but too low... maybe 24 PSI
