The most common reason for tough, rubbery pancakes is overmixing, which causes too much gluten in the batter. Mixing the wet and dry ingredients together forms glutens. These are strands of protein molecules that build the structure of cakes, breads, and other baked goods. A little gluten is good because it forms a loose, flexible structure and traps the bubbles from the C02 gas released by the baking powder. This makes your pancakes rise and become fluffy. But as you continue mixing, the glutens bond and form a tight, dense structure, leading to tough, chewy pancakes.