Brake Master Cylinder Help Needed!

[Hill Bullock]

Hey Folks,

I have a question on brakes and master cylinders. My car has separate master cylinders, one for the front brakes and one for the rear. My brakes have never been very strong (bought the car turnkey), but someone with the same kit who has the same rotors and calipers, said my brakes should be much stronger than they were.

Analyzing the setup, I noticed the front master was 7/8 and the rears were 3/4. From everything I had heard, to keep the brakes biased to the front, the front master should be smaller. While looking at the 7/8, I noticed it was leaking and that there was a flaw in the cylinder.

I went to Racer Parts Wholesale online to get a replacement master. Since the 3/4 was okay, I could either get a 7/8 and end up moving both masters, or I could get a 5/8 and put it in the front, leaving the 3/4 in the rear.

As a side note, I also ordered some braided steel brakes hoses for the front, hoping that getting rid of the rubber flex would add some brake power.

This weekend a friend of mine and I installed the 5/8 on the front with the 3/4 on the rear. We also managed to get one of the braided steel lines installed, but not the other side as the person who had built the car had tightened one of the connections down to the point where we were stripping the crap out of it trying to get it off.

Anyway, we bled the fronts and got all the air out, but it would never develop any real pressure. The pedal would go to the floor every time (with some effort). The 5/8 master is supposed to require more travel, but give more braking force, in theory. But is 5/8 too small? Is it requiring so much travel that I am getting to the floor before it firms up? There were no leaks anywhere that we found, and pumping/bleeding yielded nothing but fluid.

Suggestions?

Thanks!

[niles]

Without knowing more; such as, how big are the pistons in the front; etc to determine if the 5/8 was running out of volume before pressing out the slack in the pistons.
Tell me your observations relative to the following: If your pedal firms up after 1 or 2 in of travel and the brakes start dragging; more pedal pressure doesn't increase greatly the braking force; just the pedal continues down without much change in braking.

Then a likely candidate is a small bubble being compressed.
I have seen examples of where normal bleediing will not remove a air pocket because it in a high spot. The solution if this happens to be the case is you need to remove the calibre and lock it with a metal spacer the same thickness as the rotor and rotate the calibre while bleeding such that the bleed screw is exactly at top, forceing any stray air to the bleed screw hole.
gn