Well, today was the day I decided to tackle my Brembo 38/42 brake pedal travel on my Alfa Spider...mainly due to the fact I nearly mounted Contigo's GTS during a spirited drive in Wales over Xmas.
Whats been happening is I have referred all the callipers, discs and pads plus replaced all the fluid and bled and bled and bled but still have excessive brake pedal travel.
It went to the local garage in the end who bled it, then bled it again, and once more for luck. We know this....there is no air in the system!
What the garage did that was clever was to clamp off each flex brake pipe in turn to isolate the problem and rule out the master cylinder, servo and any other part of the system.
When clamping off the front callipers, the pedal went firm which points to the problem being 100% with the front callipers.
So, yesterday, in readiness for summer, I decided to get on with it.
I remove the front callipers, which will be taken apart again and have another set of seals and dust cover plus replace the front hoses.
So, callipers came off easy but the hoses where they connect to the brake pipe was seized solid on both sides. I use heat and the correct slotted 11mm brake pipe spanner but it still jumped and rounded off. In the end I had to cut them off which means I have to now replace the brake pipes all the way back to the ABS unit. Its not costly, got the copper kit which you bend into place for £35 delivered from
http://www.automec.co.uk who were really helpful. They did not have a kit registered for the GTV 3.2 so I had to remove mine (nightmare) and measure them with a piece of string to get the length. The near side is 40" and the off side 66" with M10 fine (1.0) thread short (15-17mm) male connectors.
The difficulty is access. In the end I had to cut the longer one in 2 places to get it out and am not looking forward to refitting them. The ones going back in are copper and very malleable but I am expecting a lot of swearing and cut knuckles.
Once this is done, I will strip the callipers and replace the seals again and also adjust the over return this Brembos seem to have issues with:
The pistons in a brake caliper depend on the distortion of the D shaped seal to return them to the brakes off or resting position. When changing pads on these cars great care should be taken not to push the pistons back too far in the caliper to get the old pads out. You should just push them back sufficiently to release the old pads. If you don't do this, stiction of seals on the caliper bore can cause the piston to move forward but not bring the seal with it down the bore surface & cause the piston to over return when you release the brakes. You then need more fluid to bring the pads back in contact with the disc (rotor) which gives you a low or mushy pedal
Partially worn rear pads & new fronts leaves you with greater fluid requirement to engage the rears than the front. This unbalances the 2 circuits requiring just one light pump of the pedal to regain the ideal pedal movement or firmness of pedal. It's hit and miss depending on stiction in the rear calipers. Sometimes you get away with it & sometimes you don't. You have no idea how many cars this plagues. Mine included.
Your braking bias front to rear is correct but has nothing to do with this situation.
BTW - the term stiction comes from the shock absorber industry & describes the stick/slip action of seals on the shaft. The sames applies to the action of the D shaped cross section seal on a caliper piston operating in the bore. The D section seal looks a bit like an O Ring. If it sticks to the bore instead of sliding down the bore you suffer over return. We are talking pretty small movements here.
You are lucky you don't own an Alfa - they are chronic for doing this. Our cars don't do it as badly but it's irritating nevertheless. I would have said it was a Brembo thing but older Alfa's with Lockheed Bonaldi brakes were even worse.
Its never easy its it!