BB drop measures how far the bottom bracket (where your cranks attach) sits below an imaginary line drawn between your front and rear wheel axles. It affects two key things: how stable the bike feels and whether your pedals might hit the ground in tight corners.
A higher BB drop (72–75mm) lowers your center of gravity, which can feel more stable and planted at speed. The downside is less pedal clearance when cornering — you're more likely to experience pedal strike if you're leaning hard into a turn. A lower BB drop (65–70mm) gives you more cornering clearance but raises your riding position slightly.
Most road bikes land in the 68–72mm range, which balances both traits well for everyday riding. If you're racing criteriums with fast, tight corners, lean toward the lower end to avoid pedal strike. For steady endurance rides and gran fondos, a slightly higher drop often feels more confident. For most shoppers, this spec is a tiebreaker rather than a dealbreaker.