23 mm Master cylinder?, From a 930? Options

[HalfMoon]

A friend of mine who owns a race shop that does alot of Porsche work said when queried about reducing travel on the 914 brake system that the 23mm master cylinder from a 930 would far better reduce the travel over a 19mm master cylinder.
Has anyone done this mod and if so, what were the performance gains/differences?
Thanks
D

[Dave_Darling]

When you change the diameter of the master cylinder, you are changing the hydraulic advantage over the brake pads. The effect is almost exactly the same as shortening the arm on the pedal. You get less travel but you have to push harder for the same clamping force.

--DD

[tomeric914]

...on a bone stock brake system

When you change the diameter of the master cylinder, you are changing the hydraulic advantage over the brake pads. The effect is almost exactly the same as shortening the arm on the pedal. You get less travel but you have to push harder for the same clamping force.

--DD

[Dave_Darling]

...on a bone stock brake system

No, that's on any brake system. If you keep the rest of the system the same in either case, you have to push harder and get less travel. Period. (Up until you have such a massive disproportion between master cylinder and caliper diameters that you cannot move enough fluid to actuate the brakes.)

The same applies in reverse if you just change out the calipers for those with larger piston diameters. You effectively make it the same as a longer lever on the pedal, meaning you do not have to press as hard but you have to move the pedal a greater distance.


The real question is, how is the pedal throw/pedal effort tradeoff to each individual driver? That's a very subjective question...

--DD

[tomeric914]

The reason for going with a larger master cylinder is that something else in the brake system has changed. In my case, I changed out the front and rear calipers to those which have piston areas equal to a 911 which goes to your statement in BOLD below. Please read my write-up.

...on a bone stock brake system

No, that's on any brake system. If you keep the rest of the system the same in either case, you have to push harder and get less travel. Period. (Up until you have such a massive disproportion between master cylinder and caliper diameters that you cannot move enough fluid to actuate the brakes.)

The same applies in reverse if you just change out the calipers for those with larger piston diameters. You effectively make it the same as a longer lever on the pedal, meaning you do not have to press as hard but you have to move the pedal a greater distance.


The real question is, how is the pedal throw/pedal effort tradeoff to each individual driver? That's a very subjective question...

--DD