1965 Dart front disc brake conversion low brake pedal

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Stumpy

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So I had a shop install the Dr Diff front disc brake kit. I had a cast iron disc/drum brake master cylinder laying around that I bought in error when I replaced the single pot master cylinder a couple years ago so I had them install that. Also installed the correct proportioning valve.

Everything works. It brakes well, with nice pedal feel. I think the pedal is too low when depressed. The pedal arm sits about an inch off the carpet when fully depressed.

When I got it home from the shop, I noticed the brake lights were out. Turns out the brake pedal was a couple cm forward than when I brought it in so it wasn't making contact with the stop light switch. I adjusted the switch.

The other problem is when I tested braking on gravel the rear drums seem to lock up slightly before the front discs. I want to test this on wet pavement to make sure.

I didn't replace the brake master cylinder push rod. It still has the stock rod. Maybe this is why the pedal arm was a couple cm forward from the original position? Should I replace the rod with an adjustable? Could this cause the rear brakes engaging before the fronts?

If so what rod do people suggest? If not what should I do to chase down these two issues.
 
How far UP is the pedal at rest? Can you pull it up any by hand? You may simply need to adjust the length of the master cylinder rod.
 
How far UP is the pedal at rest? Can you pull it up any by hand? You may simply need to adjust the length of the master cylinder rod.
It’s up nearly as much as it was when I brought it in. It is about 2 cm down from where it was. Is the stock rod adjustable?
 
It’s up nearly as much as it was when I brought it in. It is about 2 cm down from where it was. Is the stock rod adjustable?
How on Earth would I know that when the car is where you are? You're going to have to exert yourself and actually look. I bring it up because sometimes there are slight variations in machining and tolerances in master cylinders and sometimes the pedal can slightly change positions. Just as an example, I replaced the master cylinder on my Ford truck several years ago. Upon initial test drive, it was fine. But the longer I drove it, the more I realized the front brakes were trying to lock down. I ended up slightly shortening the rod between the booster and master cylinder, as the new master cylinder's dimensions were slightly different and it was barely applying the front brakes sitting static. Although yours would be in the opposite direction, it's worth looking at. Unfortunately, since this is the internet, I cannot do that for you. I think some of them are adjustable and some are not.
 
It’s up nearly as much as it was when I brought it in. It is about 2 cm down from where it was. Is the stock rod adjustable?
2cm. I had to look it up. That's gettin close to a full inch. Like .787" That's a ton. So if the pedal rod is adjustable, that could solve your issue.
 
How on Earth would I know that when the car is where you are? You're going to have to exert yourself and actually look. I bring it up because sometimes there are slight variations in machining and tolerances in master cylinders and sometimes the pedal can slightly change positions. Just as an example, I replaced the master cylinder on my Ford truck several years ago. Upon initial test drive, it was fine. But the longer I drove it, the more I realized the front brakes were trying to lock down. I ended up slightly shortening the rod between the booster and master cylinder, as the new master cylinder's dimensions were slightly different and it was barely applying the front brakes sitting static. Although yours would be in the opposite direction, it's worth looking at. Unfortunately, since this is the internet, I cannot do that for you. I think some of them are adjustable and some are not.

From what I can see the rod is not adjustable. I thought maybe I was missing something. I think I will try an adjustable rod.
 
From what I can see the rod is not adjustable. I thought maybe I was missing something. I think I will try an adjustable rod.
Can you tell how much "play" you have before you actually start pushing the piston in on the master cylinder? If you have little to none, the adjustable rod might be a waste of money. If there's some play there, then it could help. You don't want to have it too long so that it hangs the brakes on at all.
 
Can you tell how much "play" you have before you actually start pushing the piston in on the master cylinder? If you have little to none, the adjustable rod might be a waste of money. If there's some play there, then it could help. You don't want to have it too long so that it hangs the brakes on at all.

I don't know. I suppose I'd have to drain and look in the MC to tell for sure? Is there another way to tell? From full neutral to where the brake pedal starts getting hard to push by hand, the pedal play is about 2.5".
 
I don't know. I suppose I'd have to drain and look in the MC to tell for sure? Is there another way to tell? From full neutral to where the brake pedal starts getting hard to push by hand, the pedal play is about 2.5".

It almost sounds like you got the wrong master cylinder.
 
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