Granada Front Disc, 9” Drum Rear, 86 Bronco II MC, and Manual Brakes - Pedal Slack

AeroCoupe

lube between the nut and the face
Founding Member
Oct 28, 2001
2,504
1,459
153
Claremore, OK
Buddy has the car and it’s a 69 Sportsroof which is dad owned and was the one that installed the Granda front brakes. His dad used the orginal drum/drum MC and it was bypassing so we installed a new MC for an 86 Bronco II with manual brakes. After installation there is about 2” of slack in the brake pedal and then it’s solid. We bench bled the new MC and bled the brakes with my Motive power bleeder.

I know drum brake adjustment will slack the pedal and they are properly adjusted. My doubt is with the Granada disc brake setup. I’m used to floating calipers on pins and the Granadas are a bit different. Is it possible for them to be stuck and the piston having to travel farther than normal to engage? I know the bleeders are correct as they are facing the rear of the car so we did get all the air out of them. The way the calipers slide on the spindle is suspect to me in that I do not think any anti-seize or lube was applied. His dad cannot remember if he used new calipers or the ones of the donor car which leads me to believe that he used the donor car units and possibly the soft lines as well.

We removed the rod from the old drum/drum MC by cutting it apart but the inside was nasty.

1688852039671.jpeg


I’m starting to think this crap is also in the front calipers and combination valve. I think I have him convinced he needs to get new calipers and we need to clean the combination valve. IF the combination valve has issues we will most likely gut it and install a manual proportioning valve but I would like to avoid that as he wants this car simple. There may even be an issue with the front soft lines (rubber lines from the body hard lines to the calipers) being old and soft so if we do calipers those will be replaced as well. When we bled the system we ran over a quart of fluid through it and the fluid was clear when we finished. Doesn't mean the calipers and combination valve were clean but just thought I would throw that out there.

Anyhow any suggestions (other than bleeding the MC and lines as we have beat that up) would be appreciated.

He had manual brakes on his 86 GT and the brakes on it were fantastic. Stock 87-93 front brakes and 9” rear drum brakes with a 93 Cobra MC. Had a 408 with nitrous and the brakes were more than capable to slow the car to make the first turn out with ease. His 68 Mustang was drum/drum manual brake car and he said the pedal did not have this kind of slack. Being he has driven manual brake cars before he is not happy with the pedal slack this one has.

The car stops good now with the new MC and the nose dives down a harder than it did before which is telling me the front brakes are now doing the majority of the braking as I am pretty sure they were not working with the old MC. It’s just the slack in the pedal he does not like and it’s not confidence inspiring at all.
 
Last edited:
  • Sponsors (?)


We are going to adjust the rear brakes tight so the drums cannot turn and then check the pedal slack. Next we are going to recheck the brake push rod and ensure that is it in fact long enough to fully stroke the MC. After that we are going to watch the front caliper pistons and see how far they are traveling to engage the pads to the rotors. My guess is its the front calipers just about seized up on the spindles. This type of caliper was used up into the late 80's on the F150's so Ford liked the design but calipers on pins are a far superior design. My other guess is that his father (originally installed the Granada setup) probably used the calipers off the donor car so there may be issues with them. Will clean up the contact areas on the spindles and the existing calipers and see what that does for operability and if that doesn't pan out then replace them. If we replace them then I will remove the combination valve, tear it down, clean, reassemble, and reinstall and check again. His dad did mention he never liked the brakes on the car.... :doh:
 
So he runs bigs and littles on it with drag radials. 408W with a shot of nitrous and a reverse manual valve body C4. All he is worried about is making the local cruises and hitting the drag strip so no big blingy brakes as they will not fit behind the wheels. Gotta get what he has working.
 
  • Like
Reactions: 1 user