Brake pedal height question

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my68barracuda

my68barracuda

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I have the 73 and up disks on the front, 10.95 rotors with the 2.75 inch diameter caliper pistons and the Dr Diff rear disk brakes on the back.
The master cylinder is the Dr Diff 15/16 piston unit. going from the stock 4 bolt MC to the 2 bolt MC I used the Dr Diff adapter. I also believe that re used the stock MC push rod.

The car stops OK, certainly nothing outstanding, I am considering changing to the 11.75 front rotors and some performance front brake pads, currently the front pads are basic OE parts.
but that is not my question.

It has always seemed to me that the brake pedal height was a bit low in the car. I measured it today and the brake pedal with no pressure on it is 5 to 5.5 inches, measuring from the carpet to the top of the pedal.
Using a lot of hand - arm pressure on the brake pedal and again measuring from the carpet to the top of the brake pedal I get 2 to 2.5 inches.

I know that putting all the foot pressure that I can muster, I cannot get the brake pedal to bottom out on the carpet-floor, which is good.

So is a brake pedal travel of 2 to 3 inches sound right? And does a free height of 5 to 5.5 inches sound right?
I have aftermarket seats in the car, so perhaps to get the brake pedal where I want, I should raise the brake pedal pad.
just asking to see if these measurements are typical and sound right.

Thanks
 
This is stock 1" mc and KH front disk.
Pressed hard but not two foot hard.

My rear brakes are not adjusted correctly right now. The pedal went down to close to 2 to 3 inches from the floor. The measurement photo was after a double pump.

BTW I find the pedal to be a bit high and I tend to bump it with my foot going from gas to brake.


15/16 " mc will travel farther but need less pressure to get the same brake effect.

PXL_20221216_024455255.jpg


PXL_20221216_024412226.jpg
 
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You might check your rear brake adjustment, to bring the depressed pedal height up a bit.
 
my68barracuda said:
I have disks on the back
Click to expand...
Good point:D (slapping myself on forehead)

I adapted rear disk brakes from 80s Lincoln Versailles to a Ford 9"

The piston had a special tool and a procedure to set the pad properly.

Don't know anything about the kit you used but might still look at the rear adjustment if it has built in e brake.
 
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It does have a built in e brake, the Dr Diff kits are based on Mustang Cobra calipers. I will look into that.
 
I've seen a lot of rear disc conversions and done several. I've YET to see one that I thought I liked the pedal feel on. Always came out what I call spongy. Maybe that's just one of the differences between drum to disc, I don't know, but I never have liked the feel. Thing is, most people will never, ever, EVER use the 4 wheel disc system to its capacity on the street, so a lot of times, it's.....maybe not money wasted, but IMO money that couldda been "better spent". It has just always seemed to me that 4 wheel discs was just one more thing to add to the list of things to bench race with.
 
Dana67Dart said:
Good point:D (slapping myself on forehead)

I adapted rear disk brakes from 80s Lincoln Versailles to a Ford 9"

The piston had a special tool and a procedure to set the pad properly.

Don't know anything about the kit you used but might still look at the rear adjustment if it has built in e brake.
Click to expand...
Watched a YouTube video on changing the rear brake pads on a cobra mustang. They used a special tool that turned the caliper piston as opposed to using a C clamp. Seems that the cobra caliper piston ratchets as it moves out. But all they did was spin the piston in to make room for the new thicker pads, no real ‘adjustment’. Is there more to it?
 
I have the same set up and my pedal is rock hard. Like others have said, make sure you have the rear brakes adjusted by pulling on the emergency brake several times to take up any slack.

Compared to the nine inch drums that I took off, my car stops on a dime. Compared to my new truck with power assist four wheel discs and anti-lock brakes it is quite primitive.
 
Brake light switch location? Not much adjustment there.
 
my68barracuda said:
Watched a YouTube video on changing the rear brake pads on a cobra mustang. They used a special tool that turned the caliper piston as opposed to using a C clamp. Seems that the cobra caliper piston ratchets as it moves out. But all they did was spin the piston in to make room for the new thicker pads, no real ‘adjustment’. Is there more to
Click to expand...
That sounds like the ones from the 80s. doing more thinking (it's been a LONG time) they auto adjust out as you noted.
Probably not the issue.

Might be a non, issue just something to get used to. Like how some cars have extremely touchy brakes, the first few miles of driving people are tossed thru the windshield but after a while you get the feel for it.
 
BrianT said:
I have the same set up and my pedal is rock hard. Like others have said, make sure you have the rear brakes adjusted by pulling on the emergency brake several times to take up any slack.

Compared to the nine inch drums that I took off, my car stops on a dime. Compared to my new truck with power assist four wheel discs and anti-lock brakes it is quite primitive.
Click to expand...
"I have the same set up and my pedal is rock hard."
and I am not sure where the soft pedal comments are coming from, I never said that. The pedal resistance is fine. I my question has to do with free pedal height.
Thanks
 
Hope you are using a Disc to Disc junction block, instead of the original Disc to Drum junction block.

Discs take 3000 psi to operate, Drums take 300 psi to operate.
 
Manual brakes? Most likely cause of excess pedal travel is the m/c itself. May or may not be adjustable. When you push on the pedal, the seal has to close off the compensating port in the m/c before any pressure in the system is developed. If the piston/seal has to travel a long distance before this happens, you feel it as a lot of pedal travel.
 
Not an issue with excessive pedal travel either, as stated in the first post as well as post #14, the issue is the height of the brake pedal in the free state.
 
my68barracuda said:
Not an issue with excessive pedal travel either, as stated in the first post as well as post #14, the issue is the height of the brake pedal in the free state.
Click to expand...

I think that may have been a response after reading your first post, that with arm pressure you measured 3 inches travel, that is alarming to folks that are used to the pedal being near the top.
Disk brakes need very little volume of fluid (travel) to apply pressure, - when properly bled, and adjusted .
Cheers .
 
I have brake pressure gauges mounted in the car that show pressure right at the MC for the front and rear brake system. They both pick up immediately and show pressure on the gauges upon moving the pedal, and the pedal movement does not seem excessive, at full leg strength push I am no where near bottoming out the pedal.

A direct copy from the first post is: So is a brake pedal travel of 2 to 3 inches sound right, was not saying that the brake had to be depressed that far to get the brakes to apply. The 2 to 3 inches was total travel,

Post #2 shows about an inch and a half of travel, that guy said Pressed hard but not two foot hard. So that is probably in line with what I have

I probably have stronger than average arms, I was close to full brake pressures, had 650 PSI on the gauges with my arm pressure when I took my measurements. I can get 850 psi when I jamb on it with my leg.


Let me re phrase the question,
would going to an adjustable brake rod allow me to set the height of the brake pedal higher?
 
Good Question John,

I have the Same issue in Grune Holle.. Pedal is low compared to any stock Mopar stuff.
 
I was thinking that if you used the MC adapter, it would move the MC out the thickness of the adapter. Maybe like was said, try the adjustable push rod.
 
my68barracuda said:
"I have the same set up and my pedal is rock hard."
and I am not sure where the soft pedal comments are coming from, I never said that. The pedal resistance is fine. I my question has to do with free pedal height.
Thanks
Click to expand...
OK my bad. I'll shut up now. lol
 
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