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Brakes, HELP!!!

sta500666

sta500666

1/2 ton status
Joined
Apr 16, 2004
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Location
Dubuque/Ames, Iowa
Just converted my 14-Bolt Full-Float to disc, blead through 64 ounces of brake fluid, and still spoungy brakes... wtf? I dont know if this matters but when I put the calipers on the brackets I have from ruff stuff specialties make the outside brake shoe fit tight.

Anyone know why my brakes are still so soft???
 
Are you still using the factory master cylinder? If so that's your problem.

The new calipers require a larger volume of fluid to push the piston out where the old wheel cylinders took much less fluid to push the shoes. The stock master cylinder piston is to small to move the amount of fluid needed. Someone should chime in with the part number for the M/C you need.
 
a 73-76 vette master cylinder will work. it was an all disc master cylinder and will bolt right in and needs no line adapters.
 
its an 86 k5, I thought it could be the master cylinder... Do I need to use that vette master cylinder, cuz it sounds expencive haha. Will a 3/4 ton chevy master cylinder work??
 
No, in this case it will need the vette master cylinder. Basically, you have to have a master cylinder that is designed to push the fluid to four disc brake calipers, not just the front two.
 
I just intstalled a 1 ton master from an 80s pickup, and they work perfect. I am running a 60/ 14 bolt in an 88 k5.
 
mudboggink5 said:
I just intstalled a 1 ton master from an 80s pickup, and they work perfect. I am running a 60/ 14 bolt in an 88 k5.
Click to expand...
But do you have the 14 bolt converted to disc brake? That is the issue he is having.
 
I'd suggest an adjustable proportioning valve - you can get one from Summit. That way you can tune the brake system to what you need.

A reman '74 Vette MC is $29 with the core charge from Autozone.
 
alright, thanks for the info, too bad I wont beable to work on it for a week... I've been tryin to get this project done over the summer before I headed back to college but i guess its ganna have to wait a while

Do a lot of people use the vette MC with the rear disc conversion??
 
I think a lot of people just live with the mushy original MC, but that's just speculation on my part.
 
If you're using Caddy calipers out back, then don't go spending any money just yet. If you don't adjust the rear e-brakes correctly you will never get a firm pedal.

Read this old thread for the solution. :cool:
 
Well I can push my pedal to the floor, so there is no way i am just going to live with that! I have new/remanufactured chevy 3/4 ton front calipers that I mounted in back... they are the bigger of the 3/4 ton calipers. I'm also using new rubber caliper lines out back.

Does it matter with power brakes wheather the engine is on or not when you bleed??
 
JEBSR said:
Are you still using the factory master cylinder? If so that's your problem.

The new calipers require a larger volume of fluid to push the piston out where the old wheel cylinders took much less fluid to push the shoes. The stock master cylinder piston is to small to move the amount of fluid needed. Someone should chime in with the part number for the M/C you need.
Click to expand...
For some reason I didnt have to do anything to the M.C. and I have a 60/14 with disc brakes that work perfect:dunno:
 
The bigger the calipers, the bigger the problems. :( For movement of the pads, you have to push 4 large pistons out. The MC is basically just 2 small pistons, so take the ratio of piston sizes (x2 because there are 2 brakes on each axle) and multiply by the distance the pads need to travel and that is the distance the MC has to depress (assuming no air in the system and no swelling parts).

Smaller calipers in back help a lot (like the Eldorado calipers). When swapping MC, look for one with larger bore, like a 1-ton truck with 4-wheel discs. This will increase the pedal effort, but decrease the pedal travel. If you are out of travel, you have no options. If you have too much effort you can look into a hydroboost swap (or possibly a gym membership :D ).

Probably the best way to reduce pedal travel is to put drum brakes on the back. :(

That being said, I had my pedal going to the floor about a week ago after some parts swapping and it was just a bad MC.
 
there is no way i'm putting drum brakes back after all the time and effort I have spent trying to get the discs back there... i didnt mention im running 15'' wheels and had to grind down the calipers... (takes a while)...
 
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