Steeda ever so popular S550 clutch spring assist is now available with a heavy duty spring perch assembly. Therefore eliminating the chances of you breaking the factory one upon installation or removal. Your 2015-2018 Mustang comes with a 185 lb./in clutch assist spring installed from the factory. This high-rate spring is what causes such a vague and disconnected clutch pedal feel. The clutch pedal travels in a circular arc, with the spring assist in the middle of that clutch pedal travel. The middle of that motion compresses the spring initially and then allows it to extend after the first 30 degrees of travel. The combination of a high-rate assist spring and motion of the pedal during engagement causes a non-linear and sometimes confusing pedal feel. Having a non-linear pedal feel makes it hard to modulate the clutch on your Mustang get, Eco Boost or V6.