# Big brake troubleshoot



## Pcx (Dec 7, 2004)

Hello.. 

My setup last year was 6 piston brembo from a cayenne and R32 discs worked really well and the brake power was outstanding. 










Then the car was in the workshop for 8 months and not been driven other that from the floor to the dyno room.. 

When i picked it up the brake pedal was really strange. had to push it 4-6" before it was hard had brake power.. Kinda hard to explain how exactly it felt like.. and the ABS light was on. 


I got it home and took the brakes apart (was going for a upgrade) 

So now i mounted 12 piston brakes.. and new oem rear calipers. 

Same problem.. pedal falls toward the floor.. But can sustain pressure.. 

Is it my master brake cylinder? or something else?


----------



## greyhare (Dec 24, 2003)

Air in system or the calipers are too big.


----------



## Aloa (Apr 7, 2010)

Possibly you´ve got air in your system. 
Sounds like that. 

BUT: ABS light was on and you mounted a different brake system? 
12 pistons for a mkiv? seriously? 
Your master brake cylinder is for sure to small for 12 pistons. 

but that doesn´t explain your first main problem.


----------



## Pcx (Dec 7, 2004)

Hehe yea seriously.. buuut 380mm disc's sucks.. minimum wheels is 19" 

Cant understand why it is too big.. the 6 piston brembo's worked as they should.. And the 12 piston brakes are 12 small piston compared to the Brembos witch are pretty big pistons.. i would think its the same in the end.. 

But have to match the power with the brakes.. The car has 608.9 hp


----------



## Aloa (Apr 7, 2010)

What disc diameter did you drive with the 6 piston brembos? 
Has to be 342mm? 
Imo the 6 Piston is big enough for 600hp, but the disc might be to small. 

Again: Did you change your brake fluid, when you mounted the 12 pistons?


----------



## Pcx (Dec 7, 2004)

Yes the whole system was drained.. 

The disc with the 6 pistom brembo's where R32 disc's.. 334 as far as i can remember..


----------



## Aloa (Apr 7, 2010)

Brembo 6 Piston with 350mm discs should be big enough. 

Which manufacturer did the 12 piston?


----------



## Pcx (Dec 7, 2004)

Works great now.. It was air!!


----------



## Aloa (Apr 7, 2010)

:thumbup:


----------

