03 front, SVO rear brake questions

[montegoman351]

So I have a Lincoln Mark VII with the rear discs, seems to be a fairly common swap back in the day among fox owners. My air ride is going out so I am converting to coils, all SN95 front components, and 03 Cobra front brakes. I already plan on the '93 booster due to the sheer weight of the car, but am stuck when it comes to master cylinder sizing. I was thinking surely somebody here could shed some light on this and help me decide.

Thanks!

 

[Mustang5L5]

Mark 7's have hydroboost setups. Typically those offer more boost than vacuum boosters so I wouldn't change that out just yet.

There's no ideal MC here as your setup never came factory on a car. You'll need to do a little math to figure what is the best to use.

So your stock setup would be:
SVO calipers: 73mm piston
-8370mm^2 for 2calipers
SVO REAR calipers: 54mm piston
-4580mm^2 for 2 calipers

Giving you 12,950 square inches of slave piston surface area as a stock Mark 7 setup


Now, you've changed to this
99-04 COBRA 40.5mm pistons
-5152mm^2 for 2 calipers
SVO REAR calipers: 54mm piston
-4580mm^2 for 2 calipers

Now giving you 9732 square inches. If you ran your stock 1 1/8" MC, you'd have a hard pedal.

So lets look at the 94-95 GT setup which uses a 1 1/16" MC which is the next smallest size down.

94-98 GT/V6 calipers : 66mm piston
-6842mm^2 for 2 calipers
94-04 rear calipers all : 38mm pistons
-2268mm^2 for 2 calipers

That's 9110 square inches of total piston surface area using that 1 1/16 MC.

That's not too far off from the setup you would be running. I'd leave the MC alone for now and try this MC instead. Of course, undure if it will physically bolt to the Mark 7 hydroboost setup. I'm assuming yes? Not a common brake setup you are going with here, so you might have to play around with it


My info came from here if you want to play around with numbers a bit yourself
https://www.stangnet.com/mustang-fo...onversion-upgrade-thread.801400/#post-8075734

 

[montegoman351]

Now it has the Teves ABS circa 1980 something. Its gone out. Parts are made of unobtainium and the system, quite frankly, sucks.

From a little research I have done, the '93 Cobra R came with Mark VII rear brakes and an earlier version of the twin piston calipers, all with a 1" master.

 

[montegoman351]

So, by those calculations, a 1" Cobra master would net me a 15.2:1 ratio braking. Center line of the 13-17 desired ratio.

 

[Mustang5L5]

Now it has the Teves ABS circa 1980 something. Its gone out. Parts are made of unobtainium and the system, quite frankly, sucks.

From a little research I have done, the '93 Cobra R came with Mark VII rear brakes and an earlier version of the twin piston calipers, all with a 1" master.

Correct, but the 91-92 mark 7 brakes used on the 1993 cobra R used 45 mm rear pistons and 38mm 2-piston front calipers with the 1" master

99-04 Cobra front brakes are 2-piston 40.5mm calipers and the 84-90 mark 7 rear brakes are 54mm. Your working with a bit more piston surface area hence the 1 1/16" recommendation

What year Mark are you working with exactly? I'm assuming a few things here so I want to understand what you have. Do you have the 54mm or 45mm rears?

 

[montegoman351]

92 Mark VII

 

[montegoman351]

So that combo work out to 14.5:1 by my calculations. I hate a soft brake pedal and a soft clutch lol. I think the 1 1/16" would work best. Thanks for the help!

 

[Mustang5L5]

92 Mark VII

Roger that. Then you'll have to disregard some of the info I gave as it pertained to the 54mm rears. 1 1/16" is what I'd try out. Good luck.