The brief
The 520i had gone soft up front: excessive nose-dive under braking, and the front bobbing up and down after climbing a bump instead of settling. He brought it in for a check. That's worn front shock absorbers, the struts on the front of these. The strut damps the spring, it controls the body so it doesn't keep bouncing after a bump and it limits the weight transfer under braking. As the strut wears, the damping fades, so the nose dives further when you brake and the front carries on bobbing after a bump, which hurts ride quality, handling and braking stability. Shocks fade gradually so you get used to it, but it's a real safety issue, so worn ones need changing.
The diagnosis
On the lift each front strut got a bounce-and-inspect. Both were past it, weak damping, weeping, the body carrying on after a push instead of settling in one. The rears were still doing their job. When the pair on an axle have gone together, you do them as a set, a fresh strut next to a tired one gives you a car that handles differently side to side, so the call was both fronts.
The work
Both front struts were unbolted and removed, and a new genuine BMW-spec pair fitted, with the top mounts checked and renewed as needed, every fastener torqued to the manual figures. With both sides back together, the front geometry was checked and set so the new struts weren't fighting a misaligned corner. A road test confirmed the nose-dive was controlled and the bobbing gone, the front settling in one motion.
The outcome
Controlled braking with the nose staying level, no bobbing after bumps, a composed ride, and the front planted again. The 520i went home riding properly again. Worn shocks only get softer and they take ride quality, handling and braking control down with them, so doing the pair as a set reset the front end rather than leaving one side lagging the other.
