Rear disc brake conversion

M

Mean_n

Not-quite-so-new-guy
Dec 30, 2014
25
0
1
#21
Installing a prop valve will not fix your rear brake issue. Volume and pressure come from the master cylinder only.
How did your car stop before the conversion?

Are you running the stock Jimmy emergency brakes? They might be engaged and causing the drag.
If you remove the rear calipers, does the rotor turn freely. You can remove one caliper at a time to see if it is just one caliper causing the issue or both.

What master cylinder are you running?

Does the master cylinder hold pressure? Plug both ports at the master cylinder and pump the brake pedal. The pedal should become rock hard with little to NO movement. If there is excessive movement in the pedal, you have air in the master, or a bad master cylinder.
I am actually not running the emergency brakes and the car stopped fine before conversion, since the video I haven't took the calipers back off to see if the wheels turn freely but here's a video showing how there is a struggle to turn, it's like they are locked up, the car is in drive.
 
M

Mean_n

Not-quite-so-new-guy
Dec 30, 2014
25
0
1
#22
Yes you will be replacing the original disc/drum proportioning valve with the new adjustable or disc/disc one. From the info in your original post I believe this should fix your problem.
 
ssn696

ssn696

Comic Book Super Hero
Supporting Member
Jul 19, 2009
3,553
2,385
113
New Mexico
#23
Couple more basic thoughts.

Are the calipers centered on the rotors? I had to make some shims because I thought the brake pads might not wear evenly.

Are the parking brake shoes up against the rotors? You can't see this with the rotors on...

These may be peanut gallery questions...I did this conversion, but did not put the car on the road yet, so don't know if I'll hot this problem myself.
 
M

Mean_n

Not-quite-so-new-guy
Dec 30, 2014
25
0
1
#26
Guys if you watch the video you will see how I left the car in drive and recorded both sides and the resistance is has when it turns, Its like they're stuck, when I wrapped for the day it like the wheels would not turn anymore unless I got in the car to accelerated. I'm going to take them apart today before I head in to work to see if they are correctly centered. Also I am not running e brakes on this setup.
 
pontiacgp

pontiacgp

Canadian Prime Minister
Mar 31, 2006
24,631
10,055
113
Kitchener, Ontario
#27
I would remove the brake line from the calipers to see if it's a problem with the disk brake set up or if it has something to do with hydraulics in the brake system. If you do remove the brake lines to the calipers make sure you use some method to prevent the lines from losing too much brake fluid.
 
M

malibudave

Apprentice
Mar 12, 2010
88
64
18
Houston, TX
#28
If you are using the stock master cylinder for an 81 cutlass, you may be running out of fluid for your rear calipers. The front reservoir (for the rear brakes) is pretty small and the rear calipers may be draining all the fluid out of the front reservoir.

This has nothing to do with the rear calipers dragging, but it is most likely the reason your pedal goes to the floor.

The stock 24mm master cylinder is most likely too small to supply the fluid needed for the 4 wheel disc brakes. I would step up to a 1.0" bore.

I am not sure it will fit your vacuum booster, but a RIGHT HAND DRIVE (think postal truck) S-10 should be a bolt it. It is a 1.0" bore, has a large reservoir, and uses the stock brake lines fitting.

http://www.maliburacing.com/forum/viewtopic.php?f=25&t=124945

Also, double check to make sure that the bleeder screws are at the top of the caliper and not the bottom.
 

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