Abstract: A wheel cylinder for drum brakes having a mechanism for automatically adjusting the excess clearance formed between the lining on each brake shoe and the inner surface of the brake drum due to the wear of the lining. Excess clearance may be produced in different amounts by the respective (two) brake shoes. The wheel cylinder of this invention has incorporated in its cylinder body a mechanism for adjusting such excess clearance caused by each of the brake shoes. There are provided guide gears designed to rotate in accordance with piston movement and clutches making ratchet engagement with the guide gears, and the excess clearance is adjusted by the axial movement of each piston corresponding to the angle of rotation made by a new ratchet engagement. Also, clamps are provided between the brake shoes for ensuring the correct amount of piston movement corresponding to the angle of rotation. The present wheel cylinder finds best application to drum brakes for vehicles.