Fork Springs for Harley Davidson FXR 35mm forks  Sportster 84-89 Forks LOWERING KIT PROGRESSIVE SUSPENSION 10-1559 bnib ONLY FITS 35mm FXR and FXE models not later 39mm types  Harley Davidson Sportster Forks LOWERING KIT PROGRESSIVE SUSPENSION 10-1559 bnib  - ideal for shorter riders and for the latest slammed look- we also keep shorter progressive shocks in stock- too- ., Suspension should be personalized in the same way a seat or any other component of your motorcycle is tuned for comfort and performance. The Original Progressive Rate Fork Springs soak up the small road bumps, yet are firm enough to absorb the molar-rattling ones. Spring rates have been chosen to reduce front end dive during braking, yet still provide excellent ride comfort. Better yet, we warranty our fork springs for life! Progressive Rate Fork Springs have several advantages over straight rate springs. A Progressive Rate Spring has the advantage of a rising rate resistance to compression. The benefit of this is that the spring can be soft enough at the start of the travel to offer a plush ride, yet be firm enough at the end of the travel to soak up the big bumps