Here we demonstrated, on the basis of CHARMM36m, that molecular force fields are not optimized for constant pH simulations, and suggest a possible solution based on the reduction of torsional barriers. In standard MD such modifications do not cause any noticeable drawbacks but allow the λ-dependent side chain conformational sampling to converge in constant pH simulations. Combined with the optimal fitting of V MM , the force field modifications constitute an essential preparation step for any constant pH simulations. In this paper, we also shared an extensive use case, showing how slow torsions can influence the titration behavior of proteins. Our modification of CHARMM36m force field and optimal parameters for Asp, Glu, His, Lys, and C-and N-terminus can be obtained from (constantph). There we will also collect parameters and other force field modifications as long as we create and test them. We ask the researchers interested in constant pH simulations to share the parameters they have developed for new titratable groups or force fields with us, The other important aspect of constant pH simulations is preserving the charge neutrality of the simulation system. In our implementation, we achieved this by the addition of buffer particles, which retain the box neutrality upon protonation events. Here we discussed issues associated with the introduction of such buffers into the simulation system (e.g. disruption of hydrogen bond network, clustering, binding to protein, penetration into the hydrophobic region), and how to overcome those issues. The optimal parameters of buffers might slightly differ for different water models and force fields used, but the parameterization strategy described here provides a comprehensive guide to obtaining the best buffer parameters.