The GMC153 is the early 0.75" BORE BRAKE MASTER originally used on 1959 minis to approx 1963 with single front wheel cylinder per wheel drum brakes and most 997 Cooper with booster valve and 7" disc brakes. Also fits Austin A40 Farina Mk2.

Originally the top of this master cylinder would have either a removable union top shaped like a nut, or a smaller hexagonal nut shape machined into it, unfortunalty these parts are no longer available,therefore the only alternative was to have this copy made with the flat topped shape as this was the version that was made once the hexagonal nut type ceased production.

This looks much more period correct than the later cone shaped top versions, and of course is the correct bore size to suit the early brake systems.



this cylinder also has the original size small base foot



Often used by racers many years ago on certain applications such as 4 pot calipers which required more fluid and pressure, this cylinder helped as it would move more fluid for a given amount of lever travel but produce less force at calipers, brakes engage faster but weaker. The way round this was to change size of wheel cylinders or fit an adjustable brake regulator valve.

Colour is electroplated bright zinc followed by a clear hexa-valent chrome free passivate to stop surface contamination. 60mm high top tin tank, many owners fit the BHA4661 plastic master cylinder sleeve which effectively increases fluid capacity





The master cylinder is the heart of any hydraulic system, and the hardest to troubleshoot. A pedal that can be slowly pushed to the floor indicates the master cylinder is worn. Fluid dripping off either the brake or clutch pedal is a sure sign that the respective master cylinder is leaking.



Brake and clutch masters look similar with the clutch also being 0.75" bore but cannot be used for brakes as it has no internal feed return so can lock up leaving the brakes locked on when activated.





the matching early flat topped clutch master cylinder is AAU4969FLAT