Help! upgraded all brakes- car doesn't stop!

[205ash 9 1 Cars]

Hi!

 

I have upgraded all the brakes on my 205 and the brakes hardly slow the car, like almost not at all! The pedal is incredibly light and almost goes to the floor but fully down it feels like there is only around 10% braking force when i' m standing on the pedal, it doesn't actually hit the floor as if there was just air in the system. The rears will just about lock up on a wet road if i give it a lot of force but it doesn't seem like there is a lot happening up front. I have bled it manually and with an air bleeder and gone through a few litres of fluid. 

 

I have read loads of posts and gathered a lot of information but the setup I have is quite different to most.

 

-base model master cylinder/servo (19mm I believe- so same as all models except late 1.9GTI)

-front from 1.1 brakes to C2 VTS discs and calipers  (54mm caliper pistons- for reference standard 1.9GTI front are 48mm)

-rear from 1.1 drums to 1.9 rear discs using 1.6GTI front calipers (48mm pistons- again for reference standard 1.9GTI rear are 30mm)

 

The rear calipers I will change to standard 1.9GTI anyway as i can't use a cable handbrake, the setup came with the 1.9GTI axle which only used hydraulic handbrake, the car it came off also had a twin master cylinder pedal box. I also have no rear brake compensator valve which a 1.9GTI with rear discs would have. (do I really need this??)

 

I have several theories but I sometimes overthink and end up over complicating things, if anyone here who is familiar with 205 braking systems and upgrades or had overcome something similar please let me know- my next step I was thinking of changing to a pre-99 406 Master cylinder but if this isn't going to make much difference I would rather not waste the money, time and more brake fluid!  (I see from the forum that some say upgrading to this makes the pedal better, some say it makes no noticeable difference)

 

TIA!!!! Ash

 

 

 

 

 

[Anthony 1,003]

Two things that immediately jump out:

 

1. Your 19mm non-GTi MC is going to be too small with the front and rear calipers you're running, and will give you a lot of pedal travel.  I'm not sure even a 406 MC will be large enough with 1.6 calipers on the rear, but it should be much better.

2. Without some kind of compensator / bias valve, I suspect that you're going to have too much rear brake effort and the car will lock the rears up before the fronts.

 

I've not tried using 1.6 calipers on the rear and the significantly larger pistons that brings with it, but certainly a 266mm front brake setup like a C2 VTS coupled with standard 205/306 rear calipers is very effective, even with standard pads.

[205ash 9 1 Cars]

Thanks for the reply! Yes that does make sense, in my head I was thinking the issue I have is the M/C is maxing out and the amount of fluid it can physically displace at full travel is not enough to move all the pistons out very far, the rear pistons having less surface area are moving out more than the front hence why it feels the back is trying harder.

 

As I was going to change the rear calipers anyway maybe its worth fitting the 406 M/C at the same time- I haven't looked into compensators what do people normally use/recommend as a retrofit solution?