5 replies to this topic

[peasoup39]

Purchased a new after market master cy;inder for my 1978 Mini Clubman estate about a year ago. Now starting the reassembly. Went to fit the pipes to the cylinder but founf the lower pipe thread is a larger size than standard. I assume this may be to prevent putting the wrong pipe in the wrong port. How do iget around this problem and what size is it. I make my own brake pipes so if i can get the fitting i can solve the problem

[Spider]

Sounds like you might have the GMC227, aka Yellow Tag ?

The lower port on these if for the rear brakes and top for the fronts. This is because the bore in them is stepped and so they aren't really interchangeable otherwise the brake balance will be quite wrong.

The lower port on these is M12 x 1.0 and the upper is M10 x 1.0.

Mini Spares have a pipe kit that from memory, includes an adaptor for the lower port.

[peasoup39]

I have sourced M12 and M10 fittings so i can now pipe it up correctly but your comments are worrying. My car has two lines running to the back and no pressure limiting valve which suggests this a dual diagonal system. If the pistons are a different size then i will be applying more pressure to one front brake than the other. Surely this would cause the car to pull to one side whilst braking. Have i bought the wrong replacement master cylinder for this set up?

[mad4classics]

I think you need GMC167 for a diagonal split system; GMC227 is for front rear split system.

[peasoup39]

Think your right but having studied the option i can understand why they did not run the option for long. Sounds a bit dangerous to me that only one front brake working in an emergency a spin is inevitable. I have decided to repie the system to give me front to back split as the new master cylinder is fitted. My only query is does the larger piston for the rears means a lower braking force. Does this mean you do not need A COMPENSATING VALVE

[Spider]

You can't use the GMC227 in a Diagonal Split system, you need to use the GMC167, which is still available.

Though, as you have already thought about it, the diagonal split isn't wise. You can convert to a front / rear split easy enough.

If you do, you can leave the rear wheel cylinders that you have in there (they'll likely be 1/2") and then you won't need a rear shut off valve.