yeah i get what your saying Amtrapid. ABS itself shouldnt affect things as im plumbed in post ABS. But in keeping ABS, it means keeping individual circuits for each wheel. which means you need a twins or tandem handbrake cylinder. If im using a twin cylinder, then that means im effectively halving the pressure i can build because its split on 2 cylinders. (double cylinders = double the surface area = half the pressure)

But the STi tandem shouldnt suffer from that same problem. Because its cylinders are inline with each other instead of parralell, then the force thru each cylinder section should be equal to the total force on the entire cylinder. That means that im not halving the pressure generated like when going twin cylinders.

This is evident by the fact that the tandem cylinder works significantly better than the twin cylinder. Even though it uses a slightly LARGER bore. 0.625" on the twins and 0.7" on the tandem. So even though its bigger cylinder, its only working like 1 instead of 2. So its an improvement, but it just isnt enough to fully lock up.

if i had a race pedal box with front and rear cylinders, balance bar, no ABS etc, then i could use a single handbrake cylinder and make large pressure in the lines with it. No ABS and no Diagonal split braking means a single cylinder would be possible. So a single cylinder with the smallest possible bore size eg, 0.625" would make the most pressure.

But even still, it still may not lock the rear end up fully if the rear calipers are too small. The rear brakes on any road car are always gonna be pretty pathetic. (Even brembos.) Because being rear brakes, they simply arent meant to do large braking forces. Infact on a road car, they specifically try to avoid large brake forces at the rear to prevent the rear from locking up. They add rear bias valves to prevent the rear from locking up and use alot smaller piston areas, disc diameters etc. Reason is that if you lock up a front, the car will massively under steer. Its not desireable, but its manageable. but if you lock up the rear, you get a massive and very difficult to control oversteer. OEMs will do anything to avoid the latter. (although in the case of a handbrake, it is exactly what ypu are trying to achieve) Also because the weight transfer during braking means the front brakes can work alot harder than the rears before locking up.

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