How do I adjust grind size to improve my espresso?

Grind finer when: shot runs too fast (under 20 seconds) or tastes sour/thin/weak. Grind coarser when: shot runs too slow (over 35 seconds), drips unevenly, or tastes bitter/harsh. Make small adjustments — one click or step at a time — and pull one shot before tasting again. The goal is a balanced shot: sweet, with some acidity, rich body, and no harsh bitterness. Temperature and dose can also be adjusted but grind is the primary lever.