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  1. #1

    Default 86 mustang gt brake booster question 5lug rear disc related

    Ok I have an 86 gt, I'm finishing up my 5 lug rear disc conversion. I have 99 pbr dual piston up front and 95 cobra in the rear. Now I have a 93 cobra mc and brake booster but before I start "massaging " my strut tower I wanted to ask you guys with similar brake set ups does the stock booster work ok? Or is there a way I can get the bigger booster in there without damaging my strut tower? I don't want to hurt the integrity of my car long term. Any advice would be great! Thank you

  2. #2
    Moderator wraithracing's Avatar
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    In my experience the 93 booster isn't worth all the hoopla. The early cars usually take the most amount of massaging to fit the Cobra Booster. You can do a test fit to see how much if any "massaging" you need to do. Slotting the mounting holes can help too. Personally, I would run the stock booster if its in good shape, but I am sure others will disagree.

    I will also state that the 93 Cobra MC will most likely give you a stiff/short brake pedal just FYI. I have the same basic setup on my 79 PC and when it gets redone in the future, I will swap in the 94/95 Cobra 15/16" MC rather than the 93 Cobra 1" M/C. I personally prefer a bit more pedal travel to help modulate the brakes when street driving. If nothing but autocross or road racing, then a short firm pedal is fine IMHO. Good Luck!
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  3. #3

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    I just purchased a cobra booster. I have yet to install it. on my 84 I have 93 cobra brakes front and rear with a 1” master and the pedal is just too stiff it feels like manual brakes. I will report back once it’s installed. My advice would be to install it but everyone has a different preference on the pedal feel.
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  4. #4

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    Quote Originally Posted by Lowetlx View Post
    I just purchased a cobra booster. I have yet to install it. on my 84 I have 93 cobra brakes front and rear with a 1” master and the pedal is just too stiff it feels like manual brakes. I will report back once it’s installed. My advice would be to install it but everyone has a different preference on the pedal feel.
    let me know how you go about installing it, I know ultimately ill have to do something to my strut tower, I was just trying to get a feel for all options before going that route

  5. #5

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    How about a brake booster from an SVO? They were disc all the way around... Around are year models too... Don't know for sure but I'm about to be in the same boat too very soon...

  6. #6

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    I have the stock booster w/ SN Cobra brakes, works just fine. I bought an SN booster and attempted installing it, but decided it wasn't worth beating up my strut tower for.
    Thomas

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  7. #7

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    Quote Originally Posted by 85MUSTANGTGT View Post
    I have the stock booster w/ SN Cobra brakes, works just fine. I bought an SN booster and attempted installing it, but decided it wasn't worth beating up my strut tower for.
    What would you think about massaging the brake booster instead of the tower? If anything its easier to replace a booster than repair a messed up strut tower.

  8. #8

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    The SVO power booster has a pilot diameter for the m/c which is about 0.1" smaller than standard Fox and SN95 m/c have. If you use it, the m/c that will fit in it are very limited.

    95% of the time there is a brake pedal effort problem when SN95 brakes are installed on a Fox Mustang it is because the brake pads are low friction (ceramic) or the pads have not been bed into the rotors yet. When used rotors and/or pads are installed, this takes much, much longer to do.
    Jack Hidley
    Maximum Motorsports Tech Support

  9. #9

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    I have all 94 brakes except a 79 booster(I have not yet added the adjustable prop valve). It really works pretty well. Well enough that I can get tire contact to the front fender when I mash the pedal. Travel and effort both feel right to me. (Side note: I really need to get the isolator spacers for the front springs)

  10. #10
    FEP Senior Member 83gt351w's Avatar
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    I installed a 93 Cobra booster with a 94 Cobra MC. Easy to do, I’m just not sure it’s “worth” it. My brake pedal effort is really light. If I could compare it to anything, it would be like the turning effort with my old fox rack vs my new Cobra unit. Feels more sporty, and firm. IMHO, you have it already, I’d try both if you have the patience, and time.

    http://vb.foureyedpride.com/showthre...ooster+install

  11. #11
    FEP Super Member erratic50's Avatar
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    I run stock 86 booster with M1858 and one line adapter on my car. 99GT calipers with Baer rotors. Rear is 1995 GT. Adjustable proportioning valve and LMR plug. Performance friction or Hawk HPS pads (can’t remember which) — they work absolutely outstanding imo.

    You couldn’t pay me to fight with swapping boosters.


    The only thing that I might do someday is go up to 2003 Cobra style front brakes just to combat fade on repeated hard stops.

    You can do a lot one way or another on brake feel with braided steel lines vs rubber - FYI.

  12. #12

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    Quote Originally Posted by Mustang_86_gt View Post
    What would you think about massaging the brake booster instead of the tower? If anything its easier to replace a booster than repair a messed up strut tower.
    I can't say with any certainty, but I would think that you would most likely ruin the booster.

    Seems the consensus, though, is stick with the stock booster.

    For the record, I'm currently running a '95 Cobra 15/16" bore master cylinder. When I first installed the brakes I went with the Lincoln 1" bore master cylinder. I swapped mostly out of curiosity, but did noticed a slight decrease in pedal effort.
    Thomas

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  13. #13

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    [QUOTE=erratic50;1888931]I run stock 86 booster with M1858 and one line adapter on my car. 99GT calipers with Baer rotors. Rear is 1995 GT. Adjustable proportioning valve and LMR plug. Performance friction or Hawk HPS pads (can’t remember which) — they work absolutely outstanding imo.
    Well I reckon ill try running the stock on first just to see how it feels. That way if its tolerable I won't be mad I smashed my tower for no reason. If for giggles I want to change the booster is there a way to remove the master cylinder without being in the way and getting air in the lines?

  14. #14
    FEP Senior Member 83gt351w's Avatar
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    I don’t think there’s a way to do it without getting air in the lines. As for the strut tower, tapping with a ball peen hammer is all that’s needed. It follows the factory lines nicely. Doesn’t need much at all. You can’t tell I even did mine.

  15. #15

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    Quote Originally Posted by 83gt351w View Post
    I don’t think there’s a way to do it without getting air in the lines. As for the strut tower, tapping with a ball peen hammer is all that’s needed. It follows the factory lines nicely. Doesn’t need much at all. You can’t tell I even did mine.
    Would you say it was worth doing? And did you use the ball side or the hammer side lol. If I do it I just want to be as thorough as possible

  16. #16
    FEP Senior Member 83gt351w's Avatar
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    I used the ball side of the hammer. It’s a nice upgrade, brakes are really power assisted. I’d use it as you’ve already bought it, but if I were to do it over, I’d just use an 87-93 GT booster. Above I’ve posted a link to my booster install.

  17. #17

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    I have 2000 GT pbr dual piston front and 2000 Cobra rear brakes, MM braided brake hoses, and Wilwood proportioning valve, '93 Cobra MC and stock '86 booster.

    As wraithracing thought, the pedal is stiff/short. I don't mind it for now, but I may try fitting the Cobra booster and 94/95 MC as a winter project since I do have the big booster in a box. Or I may just do the MC first, and see what happens.
    Last edited by banzaibullitt; 08-29-2018 at 12:04 AM.
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  18. #18

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    I too vouch for the 15/16" master cyl bore of the 94-95 Cobras with a stock booster. It works very nicely in our cars. I'm also running 13" Cobra front brakes as well as SN95 rear discs.

    In the past I started with a 1 1/8" SVO master cylinder, as well as a 1" bore from a Lincoln Town car. Both had overly stiff brake pedals. With the SVO unit braking was extremely poor and I could not even lock up the brakes no matter how hard I tried.
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  19. #19

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    Zap's 85 GT , does your car brake better with the 15/16" MC compared to the 1" MC?
    Project "WinBacK" 1986 LX Hatchback
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    - Cobra 17x8.5's + Modded Mach1 Chin Spoiler + 83-84 Hood & Scoop/85-86 "Blackout"+ FMS Mass Air Kit+ MM Clutch Cable & Quadrant + Fiore Cable Adjuster + MM SFC's+ Wild Rides "Battle Boxes" + Explorer Intake, Converted TB & Injectors, 70 mm Mass Air Meter + BBK Ceramic Shorties + 2.5" Bassani O/R X-Pipe & Cat-Back Exhaust w/ 3" Tips + 3L27 w/ Carbon Fiber Clutches​(out of retirement) + Pistol Grip Shifter + 99-04 GT Front/00 Cobra Rear Disc Brakes

  20. #20
    FEP Super Member erratic50's Avatar
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    15/16 vs 1” is a little like splitting hairs.

    Do you want the brake engagement to feel stock-like where it’s closer to the floor or more modern where it’s right there?

    The 1” will engage sooner in the stroke and require a bit more effort.

    I have dual piston 99 calipers, Baer rotors, Hawk or performance friction pads (can’t remember right now) in front, braided lines. Summit proportioning valve and LMR plug. 95GT rear brakes with hawk pads.

    Personally I love the 1” with stock booster. They come in very similarly to my truck and I can basically stand on them — I have to try — before the brakes lock but I can lock them at will.

    If you want more pedal movement and less effort to lock use the 15/16”

    1 1/8” is near useless for practical purposes. Remember the late 70’s LTD’s with “full power” brakes that you barely touch and they launch you? Yep, that’s them.

  21. #21
    FEP Senior Member
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    Is there any downside to using the 94/95 Cobra m/c with a stock booster other than having to adapt from metric to standard threads on the brake lines?
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  22. #22

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    The SN95 m/c are better in every respect.

    They weigh less.

    You can see the fluid level and tell how dirty the fluid is without removing a sample.

    They don't leak.

    You can purchase off the shelf lines to install them.
    Jack Hidley
    Maximum Motorsports Tech Support

  23. #23

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    Quote Originally Posted by Mustang_86_gt View Post
    Ok I have an 86 gt, I'm finishing up my 5 lug rear disc conversion. I have 99 pbr dual piston up front and 95 cobra in the rear. Now I have a 93 cobra mc and brake booster but before I start "massaging " my strut tower I wanted to ask you guys with similar brake set ups does the stock booster work ok? Or is there a way I can get the bigger booster in there without damaging my strut tower? I don't want to hurt the integrity of my car long term. Any advice would be great! Thank you

    I did a 5 lug on an 1987 LX.... beat the heck outta the strut tower. Totally NOT worth it. I noticed no difference. A lot of work to make it fit.

    I will 5 lug my 1984 T-Top, and will not touch the brake booster.


    Dont waste your time

  24. #24

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    Quote Originally Posted by banzaibullitt View Post
    Zap's 85 GT , does your car brake better with the 15/16" MC compared to the 1" MC?
    My car brake pedal feels much better with the 15/16 master cylinder that I would not consider using a 1" unit again. It is very much worth the money and time to install it. The Cobra master cylinder is also much less messy and an all around better choice IMO.
    Black 1985 GT: 408w, in the 6's in the 1/8 mile
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  25. #25
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    Quote Originally Posted by Jack Hidley View Post
    The SVO power booster has a pilot diameter for the m/c which is about 0.1" smaller than standard Fox and SN95 m/c have. If you use it, the m/c that will fit in it are very limited.

    95% of the time there is a brake pedal effort problem when SN95 brakes are installed on a Fox Mustang it is because the brake pads are low friction (ceramic) or the pads have not been bed into the rotors yet. When used rotors and/or pads are installed, this takes much, much longer to do.
    The Ford parts book lists 1 booster F0ZZ-2005-A for the all of the following applications:
    84-89 3.8L and 5.0L
    84-89 GT and SVO

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