Thread: Brake troubles

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Awful small, Jerry

Click it in post #92---------

Update Starting with basics, increasing the ratio means rebuilding the brake mount.
I very well may end up with booster of some sorts as Jerry has suggested but this is my 1st step.
I'll have a longer pedal with a shorter arm connected to the push rod. Going from 5:1 to 8:1 ratio.
This will help but I know it isn't going to fix the entire problem.

one of the reasons I was reluctant to do this was because of the lines that I'll have to replace now. $#it happens.

Went to junk yard and got complete brake setup off a Ford Explorer and will test this system before any painting ect. pic's of the new/old set and the Explorer stuff.

$85. for both sides vise $450 I spent on the new stuff that doesn't work for my app.

No-good, bad and ugly !! That's the results of changing out the bakes system to to the Ford Explorer disc brakes.

No difference in the way the brakes act. Only stops the rotors from spinning ( barely) when I hit 900 + psi and that's lots of pressure on the pedal. I even went and by-passed all the valves etc.
Jacked the front up and just a light touch of the brakes and they lock up hard ( can't turn by hand ) with under 100 psi showing. The Explorer calipers have a smaller piston than the GM calipers I thought that would make a difference but no.
2 sets same results means its got to be ?
Master cyl. 2 new ones ( disc/ disc ) have been tried 1 " and a 1.125" bore not much difference
Power booster works as tested and with out vacuum connected its very hard to hit 500 psi.
No air in system bled the system twice no air bubbles using power bleeder lots of fluid flow.
Changed the ratio on the pedal still no go.
Slight toe pressure on my 2500 dodge brakes begins to slow it down and that weights 7000 lbs. and this
won't even stop just the spinning rotors.
An the winner is ? I don't know but my ears are open.

I always wonder if I needed bigger line going to the rear, usually one line for 2 calipers. Jonathan

Originally Posted by Hotrod46

As I said earlier, I have the Explorer brake setup on my 46. Brakes work fine and the parking/emergency brake will hold the car in gear (NSRA Safety 23 test).

HotRod46: Could you please tell me exactly what parts are on your car ? Is it all Explorer on all 4 wheels ?

1" bore Corvette MC with double diaphragm 8" booster. It MAY be a 1 1/8. Sorry, I can't remember for sure. Vacuum is high. 18+ inches.

2 pound residual valves front and rear.

Adjustable proportioning valve set to max pressure (not needed)

Stock Ford brake pedal (7 or 8 to 1 ratio)

80's Thunderbird front calipers on Chassis Engineering brackets. Granada rotors.

Explorer rear brakes. Just like the ones you have.

OK. I remembered a few things while on my way to work.

The MC is a 1" bore. I wanted to change it to a 1 1/8" last year before we did the Power Tour, but couldn't find one with the correct port setup.

I started out with an 8" DD booster, but it failed and I replaced it with a 7" DD unit that I had in the shop. So the current unit is 7".

The lines are 3/16" and I'm using -3 braided stainless hoses at all 4 corners.

The pedal travel is pretty long with the stock pedal. That is the reason I wanted to go with the larger MC, but the brakes work fine and the pedal effort is very light.

Navy, I feel your pain, I was hoping to hear all was good this time around.
JMO, but the only thing left that you have not changed out is the the line to the rear itself. Is it possible the bends or something else is restricting the rear line?

This has probably been mentioned before. Assuming the same pressure on the pedal and the same pedal ratio, a smaller bore master cylinder gives more pressure, but takes a longer stroke to move the same volume of fluid. A 7/8" bore will give 1.7 times the pressure of a 1- 1/8" bore, and 1.3 times that of a 1" bore.

Navy, My front calipers have a 2.358 bore and the rears have a 1.886 bore. That alone may contribute to my success. They just aren't that different in size.

I wanted to go to a larger MC to reduce the pedal travel. With my high pedal ratio and a booster, I could afford the increase in pedal effort.

I still would call Master Power Brakes and go over your system with them, it will only cost a phone call. I still am a firm believer in swapping known good for known bad, pull off one rear caliper and one front and swap them, put a socket in if you want to simulate the rotor if they won't bolt to the brackets, neither of these will cost a dime, and will tell you if its a valving or line issue (backwards RPV?). Just my two cents worth that I have mentioned long ago, I am sorry for your trouble but throwing money at it is something I have done before as well and it is not always the solution, could be your old calipers where fine.

what is that object marked cpp? in the photos

Originally Posted by jerry clayton

what is that object marked cpp? in the photos

Classic Performance Products Adjustable Proportioning Valve w/ Brake Light Switch:
Adjustable Proportioning Blocks With Brake Light Switch

Look at the second picture down on Speedway's ad to see the logo side.

Originally Posted by Matthyj

I still would call Master Power Brakes and go over your system with them, it will only cost a phone call. I still am a firm believer in swapping known good for known bad, pull off one rear caliper and one front and swap them, put a socket in if you want to simulate the rotor if they won't bolt to the brackets, neither of these will cost a dime, and will tell you if its a valving or line issue (backwards RPV?). Just my two cents worth that I have mentioned long ago, I am sorry for your trouble but throwing money at it is something I have done before as well and it is not always the solution, could be your old calipers where fine.

I agree.