To fully enjoy Dinan performance spring sets we highly recommend pairing them up with our supplemental ride quality and handling kits. This additional kit includes tuned, progressive rate bump stops that maximize suspension travel on the lowered car for improved handling capabilities and ride quality when compared to just a spring set. By allowing for full compression travel within the spring the possibility of a sudden "bottoming out" is negated a common unwanted side effect when lowering a vehicle. Bump stops also have the added benefit of optimizing the spring rate rewarding those that use them with added mechanical grip and cornering power. Simply put, the Dinan supplemental ride quality and handling kits amplify performance and comfort when paired with performance spring sets.. Installation labor time is 7.8 hrs (RWD) or 8.2 hrs (xDrive) if supplemental ride quality & handling kit is installed by itself. Installation labor time will be negligible if installed at the same time as the corresponding Dinan Spring Set.. Dinan 17-20 BMW 340i/430i/440i/14-16 BMW 428i/435i (F30/F32/F36) Ride Quality & Handling Kit. Dinan Supplemental Ride Quality & Handling Kit - 2016-2020 BMW 340i/430i/440i. Bumpstops are made from OE quality material for progressive characteristics.. Dinan Supplemental Ride Quality & Handling Kit - 2014-2016 BMW 428i/435i. Bumpstops are carefully tuned for use with Dinan springs.. HANDLING KIT 340i 428i 435i. Includes 4 bumpstops.. Handling Kit. F30/F32/F36. DIN SBSK

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