Two things.
Stiffer is NOT rough/harsh. It means the suspension moves a shorter distance for any given bump, nothing else. The shock controls/resists speed. A stiff shock fails to move quickly enough and transmits the jolt directly to the chassis. Wham!! A spring moves smoothly.
Eibach and others (stupidly) lower the car, often onto or nearly onto the bumpstops. Little compliance there, so it will feel unusually stiff. The relationship of the center of gravity to the roll center and roll axis of most Mazdas is quite good as is the suspension geometry. Lowering a car mostly gives up compression travel (the part that makes bumps smoother), making the lowering stupid.
Stiffer is NOT rough/harsh. It means the suspension moves a shorter distance for any given bump, nothing else. The shock controls/resists speed. A stiff shock fails to move quickly enough and transmits the jolt directly to the chassis. Wham!! A spring moves smoothly.
Eibach and others (stupidly) lower the car, often onto or nearly onto the bumpstops. Little compliance there, so it will feel unusually stiff. The relationship of the center of gravity to the roll center and roll axis of most Mazdas is quite good as is the suspension geometry. Lowering a car mostly gives up compression travel (the part that makes bumps smoother), making the lowering stupid.