Originally Posted by DuaneC63

It's not a bad batch or a bad install. The factory uses rubber pads between the springs and perches. This absorbs naturally occurring spring noise. Coil- overs use a height adjustable alloy collar instead of the rubber pads in the rear (the rear of the C63 is not true coil-overs as the shock does not sit inside the coil). Hence some spring noise is transmitted into the cabin. Its a trade off for better handling. If you just use lowering spring, the pads are retained, but the shocks will wear out pretty fast.

Originally Posted by Scottie46

How fast will shocks go out with just springs on the car?

Originally Posted by DuaneC63

Scottie,
Very hard to say how many miles. Too many variables such as, how many miles do you have on the car now, what type of driving are you doing mostly, conditions of the roads in your area.