In some examples, a brake system includes a piston configured to cause a compression of a disc stack. The piston includes a piston body configured to compress a cap face of a piston cap against a pressure plate to cause the compression of the disc stack. The cap face may define a convex surface. The piston cap may be configured such that the convex surface reduces it curvature when the cap face is compressed against the pressure plate. In examples, the piston cap is configured to elastically deform to cause the cap face to reduce the curvature when the cap face is compressed against the pressure plate.