Optimization of Hydraulic Disc Brake Caliper Parameters to Achieve Near Zero Residual Drag in Two-Wheeler Brake Systems

Residual drag in hydraulic disc brake systems is an inherent phenomenon caused by elastic deformation of piston seals, geometric tolerances, and frictional interaction between piston, seal, and brake pads. Even minimal unintended pad-to-disc contact after brake release can generate residual torque, leading to increased rolling resistance, temperature rise, accelerated pad wear, and reduced vehicle efficiency. With growing emphasis on performance optimization and energy efficiency in two-wheeler applications, minimizing brake drag without affecting braking response has become an important design objective. This paper presents the design, analysis, and experimental validation of a zero-drag floating brake caliper concept developed to reduce residual brake torque through optimization of piston seal characteristics and groove geometry. The study focuses on understanding piston rollback behavior as the primary mechanism governing pad clearance after pressure release. Analytical evaluation of seal deformation and groove fill ratio was combined with controlled laboratory experimentation to quantify piston return displacement and its influence on drag torque. Baseline drag measurements were conducted using a disc rotation test setup with hydraulic actuation, followed by comparative testing of optimized configurations involving seal material modification, groove dimensional refinement, and piston surface finish improvement. Key performance parameters including residual drag torque, pressure release response, and thermal behavior were evaluated to ensure braking effectiveness was not compromised. The optimized design demonstrated a significant reduction in residual drag torque along with improved consistency in piston rollback and reduced temperature rise during free rotation conditions. The results establish clear correlations between seal design parameters and drag performance, providing practical design guidelines for cost-effective implementation in production brake systems. The proposed methodology aligns with component-level validation practices recommended by SAE International and supports the development of efficient and reliable hydraulic brake systems for modern two-wheeler platforms.