Hi Mike,
OK, no problem. Let me answer your questions and take you through my decision logic. (But only time will tell if I got it right
)
My brakes currently are all standard BMW, but I am a little different to most BMW builders as my donor car was only a 2 litre so was fitted with drum brakes at the rear.
According to realoem there are lots of options fitted to these cars with some fitted with dual bore MC's 22,20/17,46MM.....others were fitted with 20.6mm,
but that's now irrelevant as I fitted a new MC that I bought as NOS from eBay.
Unusually for BMW parts, I can't read any part numbers on it but I can now see that the back section of my current one has a larger external diameter than the front. The front piston drives the real wheel cylinders which are quite small in volume so presumably Dr. BMW decided they needed less fluid than the front disk callipers.(for the same piston travel)
My longer term strategy is to upgrade the back axle brakes to disks (but don't tell my wife
), so I opted for the 22mm bore Sierra MC.
I was close to ordering a Cortina MC with the 20.6 bore but I was concerned that when all four wheels have disk callipers they might need too much pedal travel.
Can you see my logic?
...peter