Fox Cobra Style Brake booster kit

C

Crigano

Active Member

Mar 27, 2022

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Aug 17, 2024

#1

• Aug 17, 2024

• #1

Hi all. So I just changed over to disc brakes in my 93 5.0 hatch.

I had a new cobra style brake booster and master cylinder installed.

Part: disc brake kit

https://lmr.com/item/LRS-20206K93/mustang-4-lug-rear-disc-brake-conversion-kit-1993

Part: brake booster master cylinder

https://lmr.com/item/LRS-2005CB-K/mustang-50-resto-1993-cobra-style-brake-booster-kit-87-93

The lines were bled , and theres no air but the pedal has more travel and feels softer than the original brake booster that was in the car.

Has anyone changed over to this style and had the same results?

It’s a bit spongy but I’ve never known these cars to have any other feeling lol.

 

Trogdor

5 Year Member

Aug 30, 2018

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Aug 17, 2024

#2

• Aug 17, 2024

• #2

Did you set the pushrod gap per spec?

 

C

Crigano

Active Member

Mar 27, 2022

111

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Aug 17, 2024

#3

• Aug 17, 2024

• #3

I didn’t do the install but I would assume so. The mechanic I have likes to make things perfect.

 

Mustang5L5

That is…until I whipped out my Bissell

Mod Dude

Feb 18, 2001

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Aug 17, 2024

#4

• Aug 17, 2024

• #4

That kit uses SN95 rear calipers (38mm piston)

The 93 cobra uses the stock 60mm calipers and 45mm rear calipers. With a smaller rear piston (that what the 93 Cobra would have had stock) your pedal feel should actually be a bit on the firm side as you probably should have used a 94-95 cobra 15/16” bore MC. In fact once you have this setup dialed in if you find braking response not where you’d like I’d recommend changing to the 15/16” MC



But Since your pedal is soft, it likely means you still have air in the system, and usually when a new MC is installed it likely is in the MC.

With engine off, if you pump the brake pedal, does it ever really firm up? No sponginess? Or is there still travel and give?

If so, I’d bench bleed the master cylinder again followed by a full bleed.

 

Reactions: mattcrp1 and Habu135

C

Crigano

Active Member

Mar 27, 2022

111

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Aug 17, 2024

#5

• Aug 17, 2024

• #5

with the car off, the pedal feels solid when pumping, no sponginess.

 

Reactions: Scrapla347

Mustang5L5

That is…until I whipped out my Bissell

Mod Dude

Feb 18, 2001

43,244

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Aug 18, 2024

#6

• Aug 18, 2024

• #6

What are your front brakes?

 

C

Crigano

Active Member

Mar 27, 2022

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Aug 19, 2024

#7

• Aug 19, 2024

• #7

Stock front disc brakes

 

M

mattcrp1

Active Member

Nov 16, 2023

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Aug 24, 2024

#8

• Aug 24, 2024

• #8

Do you know if they power bleed the brakes, or used the old school way? Power bleeding is usually the best.

 

C

Crigano

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Mar 27, 2022

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Aug 24, 2024

#9

• Aug 24, 2024

• #9

I’m assuming the traditional way. Not sure what power bleeding is

 

M

mattcrp1

Active Member

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Aug 24, 2024

#10

• Aug 24, 2024

• #10

It requires a machine that lightly pressurizes the master cylinder. It forces fluid from the top down. I've had very good luck getting stubborn trapt air out. Alot of service centers sell a machine brake flush for a decent price.

 

C

Crigano

Active Member

Mar 27, 2022

111

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Westchester NY

Aug 24, 2024

#11

• Aug 24, 2024

• #11

Thanks for the explanation. No, I don’t think that was done. From what I’ve researched over the past few days, it looks like this is normal pedal feel with a bigger booster.

If I want a firmer pedal, I should replace the front brakes with a 4 piston caliper from bremo, (since they’re the only ones that maker bigger brakes for a 4 lug)

 

M

mattcrp1

Active Member

Nov 16, 2023

94

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Arizona

Aug 24, 2024

#12

• Aug 24, 2024

• #12

I'm getting ready to swap new edge front calipers and rear calipers. I'll need a manual proportion valve for it.

 

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AeroCoupe

lube between the nut and the face. I know my lubes

Founding Member

Oct 28, 2001

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Aug 25, 2024

#13

• Aug 25, 2024

• #13

Pressure bleeder:

0107 Ford & Asian Import 3-Prong Power Bleeder – 1986+ Ford & Nissan

Motive 0107 3-prong power bleeder: fits 1986+ Ford, Nissan, Mitsubishi, Hyundai & Kia with 3-tab cap. 2 qt tank, one-person brake bleeding.

www.motiveproducts.com

On of the best tools I have bought.

 

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