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Soft Brake Pedal (Circle Track Mustang)
#1
Let me explain the brake system on my car.
 
Originally all Drums, manual brakes
 
Now
 
- Manual brakes
- 74 Maverick Master Cyl for Manual Disc/Drums (AutoZone)
- Proportioning valve from Disc/Drum Mustang donor car.
- Fatman 2.5" drop spindles which require:
  -- 78 Granada Rotors/Bearings/Seals/Caps (Rockauto)
  -- 78 Camaro Calipers (from Camaro Donor Car) (I hated doing that)
  -- Carbon Metallic Brake Pads (AutoZone)
- Rear Shoes (AutoZone)
- Rear Brakes are stock 9" 10"x2"
 
I've blead it 100 times
Bleed ports are on top
 
My pedal is still way too soft.  It feels like my rear brakes are working harder than my front brakes. Any suggestions?
Do I need a residual valve for the rear brakes?
The front brake lines are from a donor car too.  I'm going to replace them because weak/swelling lines can cause a soft pedal but... to me it seems more than that.
 
Any suggestions are greatly appreciated!

   
   
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#2
Have you tested pressure at the calipers?

[Image: 1_01_07_15_8_53_18.png]

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!
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#3
(05-21-2018, 04:35 PM)Jeff73Mach1 Wrote: Have you tested pressure at the calipers?

No, I have never done that.  I'm assuming they make a gauge for that, which connects to the brake line?  Any idea how much pressure it's supposed to be?
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#4
The gauge usually mounts where your bleeders go. Pressure for front brakes varies and with your combo it is hard to say, but I would think 1400psi up front and 650-750 on back brakes would be close.

I used this when I was having some issues with my set up.

https://www.summitracing.com/parts/ssb-a...gIj5_D_BwE

Master cylinder piston bore size is pretty critical in getting the proper feel. You my want to go smaller to increase pressure and get a firmer pedal, but a guage and testing would be where I would start.

I went back to semi metallic pads and my braking feels much better than with race type ceramic pads

[Image: 1_01_07_15_8_53_18.png]

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!
  Reply
#5
(05-21-2018, 05:00 PM)Jeff73Mach1 Wrote: The gauge usually mounts where your bleeders go.  Pressure for front brakes varies and with your combo it is hard to say, but I would think 1400psi up front and 650-750 on back brakes would be close.

I used this when I was having some issues with my set up.  

https://www.summitracing.com/parts/ssb-a...gIj5_D_BwE

Master cylinder piston bore size is pretty critical in getting the proper feel.  You my want to go smaller to increase pressure and get a firmer pedal, but a guage and testing would be where I would start.

I went back to semi metallic pads and my braking feels much better than with race type ceramic pads




That will definitely take out the guessing game, I will definitely try that.  You also said something else that made a lot of sense.  I have not raced on the Carbon metallic pads yet, I only tested them out in my driveway.  I have been told that they need to heat up a bit before they really start to work good.  Maybe that is also what I'm feeling.
 
Thanks for the tip!  Now to buy another tool I don ‘t have.
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#6
If you're feeling a soft pedal only in your driveway, you might want to adjust your rear brakes such that the rear wheels do not spin more than 1/2 turn with no brakes applied. That puts the adjusting wheel about where it should be for the rears, and with manual brakes, you'll have a firm pedal right off the bat.

Let me check your shorts!
http://midlifeharness.com

[Image: Flamicon2.jpg]


[Image: oldfart.png]
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#7
2nd on Midlife's post.

Drums require adjustment, especially since nobody profiles brake shoes to the drum diameter anymore.
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#8
(05-21-2018, 05:13 PM)midlife Wrote: If you're feeling a soft pedal only in your driveway, you might want to adjust your rear brakes such that the rear wheels do not spin more than 1/2 turn with no brakes applied.  That puts the adjusting wheel about where it should be for the rears, and with manual brakes, you'll have a firm pedal right off the bat.

I have adjusted the rear brakes twice. I don't think that is it. I'm going to try and adjust them again but I'm also thinking about installing a 10lb Residual Pressure Valve. I think mine was removed when I swapped Master Cylinders. The all Drum M/C probably had it inside the fitting.

Also, it's not that I only feel it in my drive way. I haven't raced with these pads yet. I'm assuming it's going to brake the same but I don't know. They might grab better when they get some heat into them. At least that is what I've been told.

Thanks for the advice!
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#9
You probably don't need a residual pressure valve. Generally not necessary with a high mounted master cylinder.

[Image: 1_01_07_15_8_53_18.png]

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!
  Reply
#10
What method did you use to bleed your brakes?

I would recommend an adjustable proportioning valve.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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