Brembo M4 Monobloc Radial Caliper vs Brembo GP4-RS Caliper

Both are cast monobloc four-piston radial calipers with 108mm spacing, so the choice comes down to piston size and weight. The M4 uses 34mm pistons and suits riders who want strong initial bite and easy pad sourcing, since it shares pads with the Ducati 1098/1198. The GP4-RS is lighter at 935g without pads, uses smaller 30mm pistons for a more progressive feel, and adds finned cooling and titanium anodizing. Buyers report both are well made; the GP4-RS is the newer design and the better step up for track use.

• Choose the Brembo M4 if you want maximum piston area, a proven pad fitment and a simple bolt-on upgrade for a Japanese or European sportbike.
• Choose the Brembo GP4-RS if you want a lighter caliper with better heat control and a more modulated lever feel for track or hard street riding.