# Pressure to swapped/big, brake calipers



## macster9090 (Jul 1, 2008)

ok so i have a technical question.. 

i have a Passat 1.8t engine code :AEB 

say i swap my front calipers with Porsche Boxter S calipers and my rear with something else that i can find that will fit.. 

Whats to say that the pressure to each caliper is the correct amount that the car is supposed to have. how do i kno that when i do apply the brakes that my brake wont just lock up when i just feather them or worse they dont stop when i apply the brake?? 

will my ABS control modual automaticaly adjust when i bleed the brakes.. 


lookin for some good advice... opcorn:

NO BS please!


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## viasevenvai (May 8, 2006)

The answer is; when you change anything with the brakes the balance from the factory will be upset. 

So, yes, the balance for the front and rear will change. ABS should prevent lock-ups though. 

THIS IS WHAT I DID: 

I replaced my front discs with larger ones. Then I put Hawk HPS pads at all 4 corners. 

My front wheels stop noticeably harder than the rears. Keep in mind the rear brakes SUCK, so if you improve them they are going to do a BETTER job in my experience. This type of balance upset is only noticeable in really severe moments of emergency braking, otherwise in straight line stops nothing is different. However if I am slightly turning and get on the brakes quickly the rear end wants to get ahead of the front, it's still pretty controllable, but you can tell it's not exactly balanced. 

I would suggest going to a track or huge parking lot to learn how the car reacts.


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## macster9090 (Jul 1, 2008)

ok thats what i thought..:banghead:..... but is there a way i can upgrade the brakes all around and then adjust the balance as if it were a track car??


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## GTijoejoe (Oct 6, 2001)

macster9090 said:


> Whats to say that the pressure to each caliper is the correct amount that the car is supposed to have. how do i kno that when i do apply the brakes that my brake wont just lock up when i just feather them or worse they dont stop when i apply the brake??
> 
> will my ABS control modual automaticaly adjust when i bleed the brakes..
> 
> ...


 modulator will not adjust, it is tuned and balanced with the OEM system. 
The pressure in your system is not depending on the wheel cylinders, meaning you didn't change you pedal, booster, engine vacuum, or master cylinder. 

You need to understand the % difference, the gain that you have changed the system. You need to judge the brake disk diameter to understand the effective radius between the two setups and the piston area difference between the two systems. (honestly you also need to know the friction mu as well to properly do it).


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## macster9090 (Jul 1, 2008)

alright im not a mechanic but if a get a book or somthing to read up on this and learn more i can. ive learnd most of the stuff for my car out of manuals and books.. any ideas and what if i did the upgrade to the front and rear. would that work?


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## GTijoejoe (Oct 6, 2001)

macster9090 said:


> alright im not a mechanic but if a get a book or somthing to read up on this and learn more i can. ive learnd most of the stuff for my car out of manuals and books.. any ideas and what if i did the upgrade to the front and rear. would that work?


 At least you're willing to learn 

http://www.google.com/products/cata...og_result&ct=result&resnum=1&ved=0CE4Q8wIwAA# 

High Peformance Brake Systems, By James Walker, Jr will give you the basic fundamentals for specing a brake system and comparing brake gain. For $9 it will be well worth your education :thumbup:


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## macster9090 (Jul 1, 2008)

thanks for the help guys:thumbup: 

and im rebuilding my Passat and i want a bigger brake kit for looks and i want it to work right! i also tend to need them as i like taking corners ect. as fast as i can!


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## macster9090 (Jul 1, 2008)

:what:what? i cant upgrade my brakes because i want the good look and quicker stopping?
common now!!


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## macster9090 (Jul 1, 2008)

aight.. well thanks for the constructive criticism, but its my car so im doin it!


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## ColoradoBob (May 5, 2000)

On my racing A4, I am running Boxster S calipers with B5 S4 rotors and Hawk HT60 pads on the front and stock rotors / calipers with Hawk Blues in the rear. ABS is currently connected and the master cylinder/booster are stock. 
It obviously is biased heavily to the front, but it stops very well, never fades and is very stable. The car would stop better with more rear brake and the plan is to upgrade the rear brakes as well. The trick will be to ensure that the balance front to rear is either neutral (ideal but tough to achieve) or balanced slightly to the front to maintain stability. The worst thing you can have is too much rear brake as it typically makes the car very unstable under hard braking. Balance can be achieved by choice of rotors and calipers (piston area), limiting pressure to the rear brakes and pad compound selection.
For the street, the biggest concern I'd have is that that the car is stable under hard braking so you can better deal with any emergency situation. For normal braking, the balance is not really an issue unless it's way off.


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## macster9090 (Jul 1, 2008)

yea. i would want to have it work properly no matter what even if it is just for show.. u never kno what could happen..


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## Kazan (Feb 4, 2005)

I find it strange that no one mentioned adjustable proportioning valves . 

http://www.jegs.com/c/Brakes-Drivetrain_Proportioning-Valves-and-Balance-Bars/10165/10002/-1

Here is a write up on installing them from a Chevy Forum .

http://www.chevyhiperformance.com/techarticles/71398_install_brake_proportioning_valve/index.html


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