Actually i would have thought just the fact youve reduced the bore by a 1mm would increase the pressure
No... Same fluid in = same fluid out.
Indeed but to increase the pressure of any liquid passing through a tube is you decrease the inner diameter.
plus you increase the speed of passage
In the pipe, yes, but you still have exactly the same quantity of fluid entering the caliper cylinder that leaves the master cylinder. Hence any improvement in braking is due to the increased stiffness of the hose wall, not the tube bore.
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