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Discussion Starter #1
I have a mark 4, base kit( can’t get completes in Canada ). So I have been using donor parts from a 1995 GT. My issue is with terrible brake stop. Can’t lock brakes and if a sudden stop is needed would probably not be nice seen,slows down but no lock. Here is my setup, stock 1995 Gt front and rear caliper,rotors, pads and pedal box. I have no proportional valve,but did I stall a wilwood valve to adjust bias front rear which does nothing in my situation. The mod has been done to change pivot by 1 1/2 inches. No booster was installed, I even modified the push rod and made it adjustable. I can’t figure out what is wrong with my manual setup. So basically do I change master to different bore, or should I just find a way to put a booster, if so, which booster do I use, master cylinder, pedal must be returned original?
 

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A different master cylinder would help you a ton as well as upgrading brake pad compounds.
 

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You've probably done this already, but I'll put it out there anyway: Make absolutely sure you have no air in the lines. I used an '04 donor, and I had to bleed the system quite a bit before the air bubbles completely stopped.
 

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Discussion Starter #5
I bleed quite a while, gravity and vacuum bleed,manual bleed, btw I have no valve just the wilwood. Original is gone
 

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I have a mark 4, base kit( can’t get completes in Canada ). So I have been using donor parts from a 1995 GT. My issue is with terrible brake stop. Can’t lock brakes and if a sudden stop is needed would probably not be nice seen,slows down but no lock. Here is my setup, stock 1995 Gt front and rear caliper,rotors, pads and pedal box. I have no proportional valve,but did I stall a wilwood valve to adjust bias front rear which does nothing in my situation. The mod has been done to change pivot by 1 1/2 inches. No booster was installed, I even modified the push rod and made it adjustable. I can’t figure out what is wrong with my manual setup. So basically do I change master to different bore, or should I just find a way to put a booster, if so, which booster do I use, master cylinder, pedal must be returned original?
I have a similar setup but with a 1991 donor. Stock MC, pedal mod, no power. Deleted stock proportionating valve so both fronts are pressured directly from MC. Recently went with Hawk HPS front pads and no trouble locking when system properly bled. It took a couple of times to get it right.
Calipers are sided so be sure they are mounted correctly so that the bleed screw is at the top.
 

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If you’re sure you’ve got the brakes properly bled, try more aggressive pads! I have ‘93 donor brakes with drums on the rear and can lock them up with OEM type pads. No booster.
 

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Are you confident the rotors are not seized?


Sent from my iPhone using Tapatalk
 

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If you are using rubber hoses one of them may be "ballooning". I had a new one that was doing this. Changed to braided stainless lines and got brakes back.
 

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EBC Yellow stuff pads. Night and day difference, literally! Make sure you break them in exactly like they tell you to. I can't believe the difference it makes. I went from horrible stopping to being able to lock them up. Again break them in like they say to.
Also the above recommendation is all based on everything is bleed properly.

Good luck,
Jim
 

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What Gordon said, smaller bore Master Cylinder and more aggressive pad will help.
Or add a brake booster.

On my Cobra, it was braking OK but required really a lot of force with the donor setup... I went Vacuum Brake booster... night and day, I love it now.

On my Daytona, brakes were way too strong (Hydroboost setup):
I reduced the Hydroboost pressure and flow from the PS pump, slightly better but still touchy
I changed the pads to less aggressive ceramic pads, better but still too touchy and still not enough rear brake
I finally replaced the stock Master Cylinder with a larger bore one with a new Proportioning Valve (Willwood MC combo), I finally have a good feeling.

Master Cylinder bore seems to go a long way... but it's not cheap.

More than anything, make sure you set the correct Front / Rear bias.... it's absolutely vital for you.
 

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I have a mark 4, base kit( can’t get completes in Canada ). So I have been using donor parts from a 1995 GT. My issue is with terrible brake stop. Can’t lock brakes and if a sudden stop is needed would probably not be nice seen,slows down but no lock. Here is my setup, stock 1995 Gt front and rear caliper,rotors, pads and pedal box. I have no proportional valve,but did I stall a wilwood valve to adjust bias front rear which does nothing in my situation. The mod has been done to change pivot by 1 1/2 inches. No booster was installed, I even modified the push rod and made it adjustable. I can’t figure out what is wrong with my manual setup. So basically do I change master to different bore, or should I just find a way to put a booster, if so, which booster do I use, master cylinder, pedal must be returned original?
Round numbers, but a 1/16 smaller master cylinder will result in 13-15% more pressure, (larger diameter)^2 / (smaller diameter)^2.
Some sort of track pad like Hawks, PFC, etc will give you 25-50% more friction. OEM stock is usually around 0.35 for friction and "track pads" are usually 0.45 and higher..
 

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I have had my MKII on the road for 14 years now with unassisted brakes for over 20,000 miles. My car has 4 wheel disc brakes, along with the Jeep master cylinder that FFR recommended for use at that time. My only additional brake modification is the addition of a proportioning valve to allow adjustment of the brake bias from front to rear. Regarding that bias adjustment, I set the valve at mid-range at time of installation and have had no reason to make changes to that setting. Unassisted braking of course requires firm activation of the pedal, but that has been no problem for me. My car has all of the Spec Racer equipment modifications except for the full roll bar, inoperable doors and smaller windscreen. I've never had it on the track. I have needed to brake in emergency situations a couple of times, and I have never locked my brakes. To me, the ability to lock brakes is not necessarily a good one since braking forces are diminished when the tires are sliding on the road. If I felt the need to test brake locking capacity, I would try it on a low traffic paved road with a light coating of sand or fine gravel on the pavement.
 

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ake sure you break them in exactly like they tell you to. I can't believe the difference it makes. I went from horrible stopping to being able to lock them up. Again break them
Jim, did you go yellow in both front and back or just the front?
 
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