Brake Master Cylinder for Dual Line Systems Mini ’78-’88

The Mini Sport Precision Brake Master Cylinder GMC227MS is a critical upgrade for owners of Minis with dual line braking systems operating between 1978 and 1988. This meticulously designed master cylinder features a stepped bore size of 17.8 to 19mm, ensuring precise control and efficient braking power across both front and rear brake systems.

Introduced to replace earlier models and improve upon them, the GMC227MS comes equipped with a failure switch on the reservoir cap, marked by a yellow identification tab, enhancing safety through improved reliability. It serves as a direct replacement for front to rear square type reservoir cylinders like GMC173/198 and GMC192/195, and it is notable for having two different size metric unions (10mm top and 12mm bottom) to accommodate the larger stepped bore size for the rear brakes.

This master cylinder requires new pipe kits for installation, specifically BAU5654LHD for left-hand drive and BAU5654 in copper nickel for right-hand drive vehicles. Additionally, the GRK1035 repair kit is compatible with this model, ensuring long-term maintenance is straightforward and efficient.

Compatibility with DOT4 or DOT5.1 brake fluid is critical, as this master cylinder is not designed for use with other fluids like Castrol SRF racing fluid or any mineral fluid. Now supplied with a new style cap GRK6009, the GMC227MS represents the pinnacle of braking system upgrades for classic Minis.