# Porsche brakes? lock up? master cylinder?



## VOLK5WGN (Nov 4, 2012)

Hey guys,

posted this in the hybrid/swap forum but didn't get as much traffic, rightfully so, there is a brakes forum.... still sorta new here... did not know there is so many different forums and sub forums everywhere :thumbup: to VWVortex

here is my question/discussion for everyone here:

helping a friend with his Mark II Golf, he wants to put porsche 944 turbo brakes on the front

currently he has girling 54 brakes, which have a 54mm piston


The 944 turbo brakes have 2(28mm) and 2(30mm) pistons in each caliper

doing some quick numbers to see how much increase we have in piston area


A=pi*r^2

girling 54 brakes
A=3.14*(54mm/2)^2
A= 2290mm^2

porsche brakes
A=2(3.14*(30mm/2)^2+3.14*(28mm/2)^2)
A=2645mm^2

the effective increase is then:

2645mm^2/2290mm^2=1.15

or 15% increase over the girling 54 brakes

my question here is, does anyone change their proportioning valves? what about the master cylinder? i see lots and lots of people put porsche brakes on their VW's but is it really bolt them on and go? (the adaptors of how you bolt them on is a different question, but much more simple then the brake pressure/bias)

i will continue to update this thread

any constructive comments/input are always welcome


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## 35i 2000 (Jan 27, 2005)

hey mate

here is a guy on the http://uk-mkivs.net 

website that put Lamborghini diablo brakes on his Mark IV Golf

they are 330mm discs with 4 pistons 2 x 40 & 2x 44mm piston diameter
































































he goes on to discuss that he is really happy with the mod and even takes it to the track

the master cyl size is 23.8mm


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## 35i 2000 (Jan 27, 2005)

here is a quick print screen of the quick excel sheet i whipped together with the numbers above.... seems like a MASSIVE increase given the stock MC


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## 35i 2000 (Jan 27, 2005)

anyone else?


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## GTijoejoe (Oct 6, 2001)

Because its an opposed caliper you don't double its effective piston area... every action is a reaction on the other side of the caliper, same with floating caliper despite no pistons on the out board bank.... hope that helps..... 

If you change the system FR and RR the same % the bias of the car won't change.

In addition, how do you know the effective radius of the new calipers are the same as the old calipers? only because they mount to the same size disk doesn't mean they are the same. piston placement......


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