Before revision:  Simulating growing actin and microtubule bundles, considering both sequential and random hydrolysis, we make quantitative predictions of the excess forces  .
After revision:  Employing an exactly solvable toy model, we analytically prove the above result for N=2. We, further, numerically show the existence of this collective phenomenon, for N>=2, in realistic models (with random and sequential hydrolysis) that simulate actin and microtubule bundle growth. We make quantitative predictions of the excess forces .