Bump (compression) damping
The damper’s resistance while compressing. More bump damping tends to speed up load transfer to the tire in transients — braking, turn-in, direction changes — which usually sharpens response and platform control while giving up compliance over bumps and kerbs. Less bump damping tends to recover mechanical grip on rough surfaces at the cost of a lazier, more floaty platform. Tune it for the surface and the transient behaviour, then let the springs carry the steady-state load.
Effect by corner phase
Front bump damping shapes turn-in response and how fast the front takes its load under braking.
Rear bump damping influences how the driven axle absorbs throttle-on load — too much tends to cost traction on rough exits.
Symptom tendencies
These describe tendencies, not rules.
The car skips or hops over kerbs and bumps
Less bump damping at the affected end tends to let the tire follow the surface again.
Entry understeer, or slow and vague turn-in Entry
More front bump damping tends to sharpen the initial response — watch grip over any bumps in braking zones.
Verify on track before you commit to a change.