bleeding brakes.

[jsimpson]

Yeah, me too. My old MGTF had manual brakes, drums at that! And it had no problems hauling down the car at any speed its 327-375hp FI Vette engine would push it to!

 

[Gunther]

Hi all
Thanks for all the input.
ChuckG, you got me worried for a moment. Thanks, I also received this confirmation about the MC bleeders.
So , bleeding the complete system in the car does not need the MC to be bled, only from the 6 each caliper bleed ports.
I saw some interesting automatic bleeders that install instead of the caliper bleed nipples and only require 1 man for the pumping bleeder procedure, which is in my oppinion the best procedure.
( personal privilege )
They are some kind of a check valve that close automatically when the brake pedal is released.
Of course, it's difficult to watch the airbubbles from the drivers seat to the right hand callipers, so still requires somehow 2 men/women.
This bleeders are pretty cheap, about 7 US$ each. ( x 6 )
I will see if the aft brakes suck air again during driving and than will have to check rotor runout play, I guess.
For the moment, the pedal feels tight.
Thanks a lot for all help.
Gunther

 

[ChuckG]

Also learned that the PB master cylinder is 1 1/8 inch ID, while the standard brake MC is 1 inch ID. Chuck

 

[jsimpson]

1-3/16 would be nice...

 

[mgms_1968]

jsimpson;

It would be better to go with a 7/8 bore instead.
The reason being that break pressure is a function of pedel force and piston area. The pedel force is the same (same for each driver) so if you have a 1 inch MC and a force of 500 lbs (at the MC) the pressure=force/area, note that area is (pi*d^2/4).

So 500/(pi*(1^2)/4)=637 psi (brake pressure).
Now if you used a bigger MC diameter your break pressure will go down. 500/(pi*((1-3/16)^2)/4)=451.5 psi

Now if you use 7/8 the pressure would be 831.5 psi.

The higher the break pressure the more force is applpied to the break pads and therefore quicker breaking (unless you lock them up).

 

[jsimpson]

Only problem with your theory is that you will run out of pedal travel before you clamp all thwe calipers. Easy pedal effort is reaaly useless when the pedal hits the floor before you stop! A larger piston, while increasing braking effort (which is not a bad thing!), also increases the volume of fluid being pushed, thereby giving some additional insurance against the brake pedal bottoming out. By the way, brakes are a LOT easier to modulate without vacuum assist than they are with vacuum assist. Power brakes are for family sedans and SUV's, not sports cars and race cars!

 

[mgms_1968]

Well yeah if you do not find the correct type of MC that has the additional reservoir capacity.

I talked to Vette Brakes about this and they mentioned that if one can find a Grand National MC it has the 7/8 bore and required capacity, but it will not bolt on directly and still have to do some fabrication work.

 

[jsimpson]

Reservoir capacity has nothing to do with running out of pedal. Only cylinder bore size affects the problem. Thanks for the GN tip!

 

[mgms_1968]

I think I understand what you are saying now.

You are talking about the capacity of the fluid with in the bore itself, right?

 

[jsimpson]

Correct! The more capacity in the bore, the less pedal travel required for braking. C-3's have notoriously little room left under the pedal when it's pushed hard!