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  1. #1
    FEP Power Member racerxmd's Avatar
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    Default Cobra Brake Booster Upgrade?

    Working on my new '85 GT T-Top car. Is there any benefit by swapping to a '93 Cobra brake booster over stock? I am doing the '93 Cobra m/c upgrade and was wondering if I should also get the brake booster?

    Thanks

  2. #2
    FEP Super Member erratic50's Avatar
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    Personally I do not see the benefit.

    I run my stock 86 booster with a Mark VII 1" bore master cyl with SN95 brakes. Dual piston 99GT calipers up front, summit adjustable proportioning valve, 95GT rears.

    Baer rotors, performance friction pads. I have a ton of control over the amount of force applied but this setup can really haul it down quickly if needed.

    While I could go to better rotors and calipers my current brakes do exceptionally well. The only thing I can see is that they would hear soak if ran really hard on a track.

    They work great so I don't see the extra effort needed to do such a swap as being worth it.

  3. #3
    FEP Power Member Mikestang's Avatar
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    Ill second the "not worth it". I've swapped a few for customers, can barely tell a diff imo.
    1986 Ford Mustang GT-

    Not much stock stuff left
    347 NA power, CNC ported heads, Extrude honed Trick Flow Intake, Custom Cam
    Suspension, custom k- member, TQ arm/pan hard rod... Much more
    Restored and ready to race, made to go fast while cornering

    1981 Mustang GT-

    Old SCCA A-Sedan National Champ car
    In the middle of rebuild

    1986 LX Sedan-

    Plans to be determined...

    "Every day I learn how much I don't know"

  4. #4
    FEP Super Member erratic50's Avatar
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    I would not bother with a 93 Cobra master cyl. The Mark VII is made of metal for better heat dicipation and it is easier to adapt and it is also 1" bore. Just my opinion.
    -- James

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  5. #5

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    Quote Originally Posted by erratic50 View Post
    I would not bother with a 93 Cobra master cyl. The Mark VII is made of metal for better heat dicipation and it is easier to adapt and it is also 1" bore. Just my opinion.
    Don't want to highkack the thread but my 79 has the stock booster and master cylinder but has the 5 lug swap and 95 plus brakes were swapped in as well as rear disks. Brake pedal is pretty soft but it stops car. Looking to greatly improve the strength and feel. Not sure i want to go hydro boost yet.

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  6. #6
    Moderator wraithracing's Avatar
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    IMHO the 93 Cobra Booster is not a requirement for good brakes. The Early 4Eye cars the booster is more of a PITA to install in my experience. The mid to late 4Eyes not as bad. I have done the Booster in two of my cars and few friends and I personally will not do another one. Just not worth the effort and labor. Your mileage may vary.

    In regards to the 93 Cobra M/C again depending on your brake setup it can be an upgrade and improvement. BUT . . . it all depends on your brake combination. I have the 93 Cobra booster & M/C on my PC with 03/04 Cobra brakes front and back and I am not a fan of the brake pedal "feel" as there is little pedal travel and modulation just has a "dead" pedal feel to me. Again your mileage may vary.

    In regards to swapping out to a Hydroboost setup. All I can say is that it is a lot of work and added expense, but once you do it, get used to different pedal feel. You will be amazed at how much brake pressure you can generate with that setup. No booster nor manual setup can ever come close.
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
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    1982 GT Stalled RestoModification
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  7. #7

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    Quote Originally Posted by wraithracing View Post
    IMHO the 93 Cobra Booster is not a requirement for good brakes. The Early 4Eye cars the booster is more of a PITA to install in my experience. The mid to late 4Eyes not as bad. I have done the Booster in two of my cars and few friends and I personally will not do another one. Just not worth the effort and labor. Your mileage may vary.

    In regards to the 93 Cobra M/C again depending on your brake setup it can be an upgrade and improvement. BUT . . . it all depends on your brake combination. I have the 93 Cobra booster & M/C on my PC with 03/04 Cobra brakes front and back and I am not a fan of the brake pedal "feel" as there is little pedal travel and modulation just has a "dead" pedal feel to me. Again your mileage may vary.

    In regards to swapping out to a Hydroboost setup. All I can say is that it is a lot of work and added expense, but once you do it, get used to different pedal feel. You will be amazed at how much brake pressure you can generate with that setup. No booster nor manual setup can ever come close.
    Weĺl that right there tells me A lot. You, still having that mushy dead brake pedal feel at times is not What I'm looking for. Right now it's impossible to heal and toe to down shift. Looks like I will go right to hydro boost.

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  8. #8
    FEP Power Member racerxmd's Avatar
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    I recently purchased a Wilwood rear brake set up w/parking brakes (12" rotors a nd 2-piston calipers). I am looking to buy the front Wilwood set up too. I am hoping that the 1" bore Cobra m/c will be the correct size.

  9. #9
    FEP Super Member erratic50's Avatar
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    The Mark VII master cyl does not feel - at all - dead on my 86. It's not mushy and it is not too little modulation either. They are well tuned to the foxbody booster as the Lincoln also runs one. The master cyl you want is #m1858.

    It's very inexpensive and easy to try one as it bolts up and one line fits. You only need one line adapter and the Mcparts store carries it.

    An LMR proportioning valve plug and a (Summit) adjustable proportioning valve is needed. I have as much rear brake dialed in as my car will hold without breaking the back tires loose before the fronts and running with no rear sway bar. Rear brake force is a ton!

    I don't know how much more stopping power anyone can generate with the better technologies as there is only so much tire under a car. I'm on a 245/45/17. It is hard for me to imagine stopping much faster. Especially the first hard stop situation. Pretty sure my friend with the 2003 cobra brakes up front can't stop any faster on the first hit.

    I don't have seat belts at the moment because I've been patching a few things. I would not want to see anyone in the passenger seat when I'm on full brakes - not even on a dare. Launching pad! I hit the steering wheel in a panic stop situation hard enough to bruise up my chest - I looked like I had been in a wreck.

  10. #10
    FEP Power Member Mikestang's Avatar
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    Default

    Quote Originally Posted by brian.aughe View Post
    Weĺl that right there tells me A lot. You, still having that mushy dead brake pedal feel at times is not What I'm looking for. Right now it's impossible to heal and toe to down shift. Looks like I will go right to hydro boost.

    Sent from my SAMSUNG-SM-G890A using Tapatalk
    Imossible because of brake pedal feel?
    1986 Ford Mustang GT-

    Not much stock stuff left
    347 NA power, CNC ported heads, Extrude honed Trick Flow Intake, Custom Cam
    Suspension, custom k- member, TQ arm/pan hard rod... Much more
    Restored and ready to race, made to go fast while cornering

    1981 Mustang GT-

    Old SCCA A-Sedan National Champ car
    In the middle of rebuild

    1986 LX Sedan-

    Plans to be determined...

    "Every day I learn how much I don't know"

  11. #11

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    I have the original 1985 booster and Lincoln mc. Running aero front brakes, turbo coupe rear brakes, gutted proportional valve with adjustable proportional valve opened about 2/3. Pedal feel is very good, close to my daily drivers 2010 Subaru Forester, 2015 Jeep Wrangler. Brakes lock when I pound the pedal.

    I had to fab up new line instead of an adapter.

  12. #12
    FEP Super Member erratic50's Avatar
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    The MarkVII master cyl is a near perfect companion to the foxbody booster. My experience is also that it's dead on. Same feel as my MKX but massively more stopping power thanks to my choice of discs and calipers and suspension and tires.

  13. #13

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    Quote Originally Posted by Mikestang View Post
    Imossible because of brake pedal feel?
    No because there is so much brake pedal travel I can't reach the gas pedal.

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  14. #14
    Moderator wraithracing's Avatar
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    Quote Originally Posted by brian.aughe View Post
    Weĺl that right there tells me A lot. You, still having that mushy dead brake pedal feel at times is not What I'm looking for. Right now it's impossible to heal and toe to down shift. Looks like I will go right to hydro boost.

    Sent from my SAMSUNG-SM-G890A using Tapatalk
    Sorry! Maybe I should have used a better descriptive term than "Dead" pedal. The pedal is stiff as can be with very little movement. My pedal does not go to the floor. The pedal is rock hard with very little travel. So it's makes it very hard to modulate the brakes because light braking to full braking is about an 1/8" (well at least it feels that way) of movement in the pedal. This is due to the 93 Cobra M/C and 1" bore. If I swap that out to a 15/16" bore such as the 94/95 Cobra unit I should have better pedal travel and more "feeling" in the brake pedal. Hope that makes more sense and clarifies my original statement.
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Stalled RestoModification
    1984 SVO Still Waiting Restoration
    1986 GT Under going Wide Body Conversion Currently

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Stalled in TX
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  15. #15

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    Reviving this older thread because it is related to my current project. Background: 1985 GT used strictly for endurance racing, up to 9 hour stints in length. Upgraded to '91 front spindles/struts/rotors, but still inadequate for 9 straight hours of road course racing with 80+ other cars. Rear shoes/drums are holding up fine and rear braking is currently optimal with stock proportioner - any more rear brake would cause lockup. Have purchased used 1994 (SN95) front spindles and lower control arms (longer to maintain -3.5 camber) from junk yard and plan to purchase new 13" rotors and Cobra (PBR?) 2-piston calipers. Will have to move to 17" 5-lug wheels up front to accommodate 13" rotor. Have many 15" performance tires (expensive) to use up before converting rear to 17", so thinking to retain the stock drums in the back for the next several races before upgrading to disk. I recognize this plan will lift front of the car by 1" due to desired 17" tire diameter will be 2" larger compared to 15" in the rear - a little weird. However, not doing this for looks, it's ALL about budget performance.

    Question: From erratic50's 2017 post above, part
    #M1858 is a Lincoln Mark VII MC with 1" bore that will bolt onto the stock 1985 GT brake booster, correct? If so, any concerns about this not working correctly with the proposed brake setup?

    2nd question: Makes sense that adding an adjustable proportioning valve in reach of the driver is needed to get the correct front/rear braking balance. Does this involve removing the stock proportioning valve? I see some reference to "plugging" the stock valve, so don't understand how that works.

    Appreciate insights from folks that have been down this road. Thx

  16. #16
    FEP Super Member erratic50's Avatar
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    One piece of info I've learned since 2017 ..... M1858 is not necessarily the best option because one brake line needs an adapter.

    Further research shows that a M1525 or 10-1525 (depending upon which parts store you go to) is a direct bolt-on. No need for any adapters or changes to the lines.

    The simplest answer is to gut the stock proportioning valve and install an adjustable. You could also simply remove it - although then you have to come up with fittings to put the lines back together.

    M1525/10-1525 is the best answer I've found for SAE line cars that need a 1" bore master cylinder.

    Both the ultimate 4 lug and 5 lug brake upgrade threads have more info that you may enjoy consuming. Good luck.

  17. #17

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    Quote Originally Posted by 85GT-EnduranceRacer View Post
    Reviving this older thread because it is related to my current project. Background: 1985 GT used strictly for endurance racing, up to 9 hour stints in length. Upgraded to '91 front spindles/struts/rotors, but still inadequate for 9 straight hours of road course racing with 80+ other cars. Rear shoes/drums are holding up fine and rear braking is currently optimal with stock proportioner - any more rear brake would cause lockup. Have purchased used 1994 (SN95) front spindles and lower control arms (longer to maintain -3.5 camber) from junk yard and plan to purchase new 13" rotors and Cobra (PBR?) 2-piston calipers. Will have to move to 17" 5-lug wheels up front to accommodate 13" rotor. Have many 15" performance tires (expensive) to use up before converting rear to 17", so thinking to retain the stock drums in the back for the next several races before upgrading to disk. I recognize this plan will lift front of the car by 1" due to desired 17" tire diameter will be 2" larger compared to 15" in the rear - a little weird. However, not doing this for looks, it's ALL about budget performance.

    Question: From erratic50's 2017 post above, part
    #M1858 is a Lincoln Mark VII MC with 1" bore that will bolt onto the stock 1985 GT brake booster, correct? If so, any concerns about this not working correctly with the proposed brake setup?

    2nd question: Makes sense that adding an adjustable proportioning valve in reach of the driver is needed to get the correct front/rear braking balance. Does this involve removing the stock proportioning valve? I see some reference to "plugging" the stock valve, so don't understand how that works.

    Appreciate insights from folks that have been down this road. Thx
    I'm running 94-98 Cobra brakes FR and Rear with the 94-98 Cobra Master cylinder and stock 86' booster, pedal feel and travel are spot on. Braking power and confidence are incredible.

    I deleted the stock proportioning valve entirely and installed the adjustable valve in it's place. Looks very clean and the bolt holes line up with the stock proportioning valve location.

    Edit: I'm also running the SN-95 A-arms with S197 17x8 wheels (+45mm offset), can turn lock to lock without any rubbing. 245/45-17's all around.
    Jeremiah

    1986 Mustang GT 5spd, 3.27's
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  18. #18
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    I switched the LCAs to SN95 on my SVO several years ago. I plan to switch over the spindles and PBR calipers next. I was told that I should switch to the Cobra MC and Booster. After reading this string, I might just leave the original SVO MC and booster. My concern was getting the adapters for the lines, to utilize the Cobra MC. I assume the the SVO MC is the same as the Mark VII MC.
    Bleed Ford Blue! '84 Grabber Orange SVO, '88 Saleen 1 of 4 w/Automatic, '89 Steeda, '71 DeTomaso Pantera GT5 Wide Body EFI 4.6 DOHC...soon to be a Gen3 Coyote and some Old Ford Muscle w/ BB power. 1.21 Jigawatts!!?? PETRO EXPRESS=CITGO=BOYCOTT!
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  19. #19
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    When you say PBR calipers do you mean the Cobra style calipers or the '99+ dual piston GT/V6 calipers? Like Two86fiveoh's I have Cobra brakes all around with the 94 Cobra MC and stock booster and it works pretty well although I haven't driven it much.

    Maximum Motorsports makes lines that go from the Cobra MC to the stock proportioning valve. https://www.maximummotorsports.com/M...ang-P1273.aspx
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  20. #20
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    The 99-04 2 piston Cobra calipers is the plan. Rear brakes are stock SVO. I was going to install a 93 Cobra MC and booster. Now, might leave the SVO MC and booster.
    Bleed Ford Blue! '84 Grabber Orange SVO, '88 Saleen 1 of 4 w/Automatic, '89 Steeda, '71 DeTomaso Pantera GT5 Wide Body EFI 4.6 DOHC...soon to be a Gen3 Coyote and some Old Ford Muscle w/ BB power. 1.21 Jigawatts!!?? PETRO EXPRESS=CITGO=BOYCOTT!
    State of Illinois - Taxation without Representation!

  21. #21

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    FYI--The 94-98 Cobra front calipers are 38mm pistons, 99-04 are 40mm. I personally went with the 94-98 front calipers and master cylinder, keeping the MC size as close to stock as possible.

    Use all factory type components, keep the system a match as designed by OEM (FR and Rear calipers/MC off the same car) and a lot of variables/potential issues are eliminated.
    Jeremiah

    1986 Mustang GT 5spd, 3.27's
    PimpXS ECU/Android Single DIN Touchscreen
    SN95 Cobra Brakes/SN95 Front LCA's/Axles/S197 Wheels
    1998 Explorer Engine/Stock HO Cam 281rwhp/326rwtq

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