The brief
The A6 had been bouncing and swaying excessively, the ride gone rough and bumpy, the car leaning to one side, the tyres wearing unevenly, and the stopping distances had stretched. Those are the signs of worn shock absorbers across the car. A shock absorber controls how the spring moves so the body settles after a bump instead of bouncing, working by pushing oil through small valves inside it. When the seals wear and the valving tires, it loses that control, so the body floats, sways and crashes over bumps, the car feels less stable, and the tyres and the braking suffer because the wheels aren't being kept planted. When the whole car feels unsettled, the shocks have generally worn together, and they only get worse from there.
The diagnosis
On the lift the shocks were checked, and bouncing each corner by hand confirmed all four had lost their rebound damping past spec, one no better than another. When they're all tired together you do the lot, shocks work as a pair across each axle and a mix of fresh and worn leaves the car behaving unevenly, so it was the full set, front and rear.
The work
All four shock absorbers came off, and a full set of genuine Audi-spec shocks went on, the mounts torqued to the manual figures, fresh top mounts where the originals were worn. A road test confirmed the bouncing and swaying were gone, the ride had settled, and the car stayed planted through corners and under braking.
The outcome
No bounce or sway, a settled, composed ride, and the car planted through corners and braking, with the tyres set to wear evenly again. The A6 went home with the suspension back to how it should ride. Shocks wear together and they take the car's composure, handling and braking stability down with them, so a fresh full set brought the whole car back to spec.