4 wheel disc questions

[SMOKEDYA]

I searched on here,and from the sounds of it since my car is 4 wheels disc. You just caint go out and buy then install a 93 cobra master cylinder and be done with it?Is this correct or not? I was reading a link to a mustang 4 disc conversion site and they make it sound like i need the cobra master cylinder plus a 2-3 port conversion (WTF is this)plus a proportioning valve also???? Am i reading correct or will just swapping out my stock 89 master cylinder out for a 93 cobra one cure the 4 wheel disc conversion?I blead the brakes after my bay project and they are mushy,i'm assuming due to the 4 wheel disc and a stock disc/drum master cylinder? peace





john

 

[Mustang5L5]

Well, if your car is 4 wheel disk, then you need to change the MC.

Which MC to use all depends on what brakes you are running. The 1993 cobra MC isn't ideal for every setup. It's just one of the easiest to install.

You may need a booster as well, but it would help first to know what you are working with before we can recommend parts

 

[SMOKEDYA]

03 cobra fronts and not 100% on the rears,but i think a t bird? peace






john

 

[Shaolin Crane]

Sounds like you should use the 95 Cobra MC, 3-2 port conversion from MM like 35 bucks, and a Cobra brake booster

 

[Mustang5L5]

That's my exactly setup.

I run a 1993 Cobra MC and booster.

 

[Shaolin Crane]

im running the 95 cobra r pair up

 

[SMOKEDYA]

That's my exactly setup.

I run a 1993 Cobra MC and booster.

so you have 03 fronts and t bird rear brakes? cool whats the diffrence between a cobra brake booster and a 5.0 booster? peace








john

 

[281pony]

Mustang5L5, this is the same car/brake setup you gave me information for. I sent you some pics I believe to show track width/caliper brackets on the rear.

 

[Chuckman]

cool whats the diffrence between a cobra brake booster and a 5.0 booster? peace








john

size. since the cobra cylinders are bigger, they need more pressure to be able to push them. the bigger the booster, the softer the pedal will feel. im running 93 cobra cylinder/booster with 04 cobra brakes/ranger drums, and that booster DEFINITLY made the car driveable, brakes were rock hard without it.

 

[SMOKEDYA]

my pedal is mushy. so by installing the cobra master cylinder and booster i'll have good pedal and braking with 4 wheel disc?peace


john

 

[Mustang5L5]

Mustang5L5, this is the same car/brake setup you gave me information for. I sent you some pics I believe to show track width/caliper brackets on the rear.

Oh, i remember that now. Wasnt it an SVO rear disk setup? 54mm calipers??

If so, that changes things. I think i said the 94-95 GT MC was the way to go for this?

Unfortunately i deleted those PM's

 

[281pony]

i think it is svo stuff. it looks alot like the setup my old fox had, and it was svo.

measure those rotors john, i think the svo stuff is 11.35". i know its atleast an 11" rotor, i took rough measurements.

 

[Mustang5L5]

Yup, u remember now. Sorry, i get a TON of PM's about brake stuff.

With the SVO rear brakes, you need a HUGE MC. The 94-95GT or the SVO are your two choices. I'd give the 1 1/16" GT MC a shot first. Pedal might be a little soft, but it will be better than the stock 21mm bore MC on there now

I'd do the 1993 Cobra booster as well.

 

[89gt89]

I'm rolling 01 pbr's in front w/01 rear's. Northracecar brackets w/stock length 5 lug axles. I have used th e SVO MC on all 3 conversions I have done and love it. You have 2 reservoirs which can be a plus. I gutted a Fairmont propvalve and plugged it. The SVO/Lincoln VII/Fairmont prop valves eliminate the need to add all that extra plumbing. They already have provision for your rear line. I addded a Wilwood adjustable prop valve in line at the coupling point next to the passenger fender. In my opinion, the stock booster has a better feeel to it. I installed a 95 booster and I feel that it's a bit much for my notch. Had to cut a mounting stud in order to squeeze it in w/o massaging mu strut tower. I'm just going to leave it as is. Anyway, my 2cents.

 

[SMOKEDYA]

Yup, u remember now. Sorry, i get a TON of PM's about brake stuff.

With the SVO rear brakes, you need a HUGE MC. The 94-95GT or the SVO are your two choices. I'd give the 1 1/16" GT MC a shot first. Pedal might be a little soft, but it will be better than the stock 21mm bore MC on there now

I'd do the 1993 Cobra booster as well.

will do i'll also measure the rear dia of the disc.Alittle soft huh? well as long as i have good braking and the pedal dont go almost to the floor i'll be happy!Thats how it is now Is the 94-95 V6 mastercylinders the same as the GT ones? Do the lines on the 94-95 master cylinders match directly up to my lines ,or do i need to redo the lines? OR would it be better to order a SVO master cylinder?If this route what year SVO matser cylinder?And same question,will the brake lines just hook right up or will i need to redo them also?If i was to put drum brakes on the rear and left the 03 cobras up front,would i still need a new master cylinder and booster?peace




john

 

[Prime Lord]

I've got 04 Cobra brakes out front and SN95 GT discs in the back. The Cobra M/C and booster are 100% necessary for pushing the Brembo twin piston calipers. You can use the the SN95 GT M/C if you are running the PBR calipers (from what I understand).

You're going to pay a pretty penny for the booster in new condition...but its well worth it.

 

[SMOKEDYA]

By useing the 95 cobra booster i gotta do some custom modifacations to make it work in a fox right? What all needs done?peace

john

 

[Mustang5L5]

Lol, too much info to comprehend.

SMoked, measure your rear rotors. If they are 11.35" in diameter, then they are the SVO rear disk. If they are about 10.5" in diameter then they are the 91-92 Mark 7/Cobra R rear disk.

WHich ones you have plays a role in what MC to use. The larger the rear calipers the larger the MC bore you will need. I beleive I told 281pony to use a 94-95 GT/V6 MC for that setup. The GT and V6 MC is the same. You can get them cheap...under $30. I've seen plenty because I was trying to sell one but decided to keep it for future use. (may go with Brembos)

As for the booster, 1993 Cobra and 1994-1995 SN95 are the same 205mm tandem booster. Only difference is the studs. Different thread pitch on the SN95 boosters and 1 stud is moved. You can prob pick up a used SN95 booster for cheap , but the 1993 cobra booster is easier to install. Just cut the studs down a little an slot the holes. You can get them new for around $100.

Your local parts stores will have these, but check out RockAuto Auto Parts as they are pretty cheap too

Now, 1993 Cobra, 94-95 GT/V6 and SVO are all going to require a 3-2 conversion. There is no one MC that is easier to install on an 87+ Mustang. You will need to purchase a 3-2 conversion kit for the MC you choose available from Maximum Motorsports :: The Leader In Mustang Performance Suspension

You will also need to purchase an adjustable prop valve, and the plug to gut the factory prop valve. With the large SVo rear disk, you'll have a TON of rear brake, so being able to turn down the pressure is key.

These are what you need

Summit Racing SUM-G3905 - Summit Racing® Brake Proportioning Valves - Overview - SummitRacing.com

or if you want the Ford Racing version for a few bucks more...same part

Ford Racing M-2328-C - Ford Racing Brake Proportioning Valves - Overview - SummitRacing.com


And the plug

Ford Racing M-2450-A - Ford Racing Brake Proportioning Valve Plugs - Overview - SummitRacing.com

 

[SMOKEDYA]

Lol, too much info to comprehend.

SMoked, measure your rear rotors. If they are 11.35" in diameter, then they are the SVO rear disk. If they are about 10.5" in diameter then they are the 91-92 Mark 7/Cobra R rear disk.

WHich ones you have plays a role in what MC to use. The larger the rear calipers the larger the MC bore you will need. I beleive I told 281pony to use a 94-95 GT/V6 MC for that setup. The GT and V6 MC is the same. You can get them cheap...under $30. I've seen plenty because I was trying to sell one but decided to keep it for future use. (may go with Brembos)

As for the booster, 1993 Cobra and 1994-1995 SN95 are the same 205mm tandem booster. Only difference is the studs. Different thread pitch on the SN95 boosters and 1 stud is moved. You can prob pick up a used SN95 booster for cheap , but the 1993 cobra booster is easier to install. Just cut the studs down a little an slot the holes. You can get them new for around $100.

Your local parts stores will have these, but check out RockAuto Auto Parts as they are pretty cheap too

Now, 1993 Cobra, 94-95 GT/V6 and SVO are all going to require a 3-2 conversion. There is no one MC that is easier to install on an 87+ Mustang. You will need to purchase a 3-2 conversion kit for the MC you choose available from Maximum Motorsports :: The Leader In Mustang Performance Suspension

You will also need to purchase an adjustable prop valve, and the plug to gut the factory prop valve. With the large SVo rear disk, you'll have a TON of rear brake, so being able to turn down the pressure is key.

These are what you need

Summit Racing SUM-G3905 - Summit Racing® Brake Proportioning Valves - Overview - SummitRacing.com

or if you want the Ford Racing version for a few bucks more...same part

Ford Racing M-2328-C - Ford Racing Brake Proportioning Valves - Overview - SummitRacing.com


And the plug

Ford Racing M-2450-A - Ford Racing Brake Proportioning Valve Plugs - Overview - SummitRacing.com

i measured the rear disc,off the car they measure 11.25 ish.SO i will need a 94/95 master cylinder and a 93 cobra booster correct? I will also need the 3-2 conversion AND one of the proprtioning valve's you listed?When i was measuring them i noticed the rear pads are dam near shot would this also cause the pedal to be mushy and go almost to the floor?Even tho i blead the brakes when i reinstalled the master cylinder after i took it off to do the bay? NOW what i dont understand is my buddy has a 89 LX hatch he converted to the 4 piston willwood system with 12" willwood rotors on his stock reaend,he is using a stock 89LX master cylinder and booster and thats it nothing else! He says his car stops on a dime and with great pedal pressure! HTF is this possible?peace





john

 

[Mustang5L5]

Master cylinder size is directly related to the area of the pistons. It's all hydraulic ratios really.

Basically, the smaller the bore MC you use, the softer the pedal will be. But go too small and it won't move enough fluid and you get a mushy feeling.

Stock MC is 21mm bore. This is fine for rear dums because the wheel cylinders require very little fluid to move far. Basically all you are moving is the front calipers. The smallest 4-wheel disk MC is the 94-95 Cobra MC at 15/16...or basically 24mm. The '93 Cobra MC is 25.5mm. The larger you go, the more fluid gets pushed and the stiffer the pedal becomes.

Which MC to use depends on the caliper piston area. So you can't go by someone else's setup if they are using different calipers. It really all depends on the total piston area.

Your setup with the 03 cobra front and the SVO rears is very unique. Basically, the stock Fox has 5654mm^2 of piston surface area (not including the tiny wheel cylinders in the rear) and now with the '03 Cobra fronts and SVO rears, you have 9732mm^2 of caliper piston area....so you nearly doubled it. You need to increase your MC bore proportionally to compensate.


Basically, here are the available MC's

87-93 fox - 21mm bore = 346mm^2
15/16 CObra = 23.8mm = 445mm^2
1" Cobra= 25.4mm = 507mm^2
1 1/16" GT/v6 = 26.98mm = 572mm^2
1 1/8" SVO = 28.5mm = 638mm^2

You have the smallest right now...reason why the pedal is mushy. Either of the two largest will be fine. The GT/V6 MC will give you a hydraulic ratio of 17.0:1...which is what the 99-04 V6's are, while the SVO MC gives you a ratio of 15.2:1...which is more ideal.

Most Factory OEM setups are ina range of 13:1 to 16:1....the lower the ratio, the firmer the pedal.