Brakes question, donor related. GT1995

[Grande]

I know most don’t use donor builds anymore, but when Canadians purchase a kit from Factory Five, no complete kits are available. That and my dream to build was a budget build. So that being said, I started with the components of a 1995 Gt. The issue is with the brakes, I am running new original rotors and pads front ,caliper from mustang 1995, master cylinder and removed the booster, modified the push rod,and pedal pivot, removed proportional valve and installed a willwood adjustable valve. Basically the car doesn’t stop safely. I would have thought hard effort is normal, but should lock the wheels and basically adjust bias. Any guys remember what was done when builds were built this way, different master? Please give me your suggestions,thanks....

[wallace18]

I would have kept the booster. Power brakes are the best way to go IMO.

[Norm B]

I had the same brake setup initially minus the the Willwood adjustable valve. I gutted the stock Mustang valve and kept it because it is required for registration where I plan to retire. Brakes were okay but not great. I tried the Whitby adjustable pushrod and that improved things a little. Could have tried different pads to get more improvement but decided to go the power brake route instead.

Very happy with the brakes now. More confident driving the car, most likely due to the fact that the brakes feel the same as our daily drivers.

If you decide to go power brakes you will need the booster for an 87-93 Mustang because the sn95 ones are too big.

HTH

Norm

[CraigS]

The easiest solution is better pads. I am familiar w/ the Hawk brand although there are others. Hawk HPS is a great compound that has good grip and very little dust. HPS 5.0 is the newer version. HP+ have even better grip but dust more. I am using them along w/ this;
https://armorall.com/products/wheels/brake-dust-repellent
I also have a dedicated small shop vac w/ a brush attachment which helps a lot. I and others have had good results running HP+ on the rear (because the mustang brakes were engineered for a front heavy car and therefore lack rear brake effectiveness on a slightly rear heavy FFR) and HPS up front.

[Grande]

Ok thanks, I thought I had heard about manual brakes and changing master cylinder bore to compensate for pedal feel, but it’s not just about the feel,it’s about the brake stopping issue. I will see if I choose the power booster option,when I take body off for paint.

[Joel Hauser]

I did a donor build with a 1996 mustang GT. I used the stock front and rear calipers, which I rebuilt with new seals from a place called discbrakesrus in Rockland MA. I did not use any of the power brake parts; It is a true manual brake system. The stock master cylinder from the 96 mustang would not work in my build (the pedal rod could not be removed or adjusted to reach the brake pedal). The good folks at FF told me to use a master cylinder for a 1987 - 1993 mustang. I got the master cylinder from Summit, part number DHB-M39637. I also had to use an adjustable pedal rod part number RSD-RC14, which I also had to modify. I am using the original rotors from the donor, and OEM stock pads (the cheap ones). It takes some getting used to, as we're so used to driving cars with power brakes, but I think my brakes work ok. I haven't had to or even tried to lock up the wheels since the car was registered a few years ago, but remember being able to intentionally lock up the wheels (on bald tires) while go carting in the driveway. It definitely takes effort though. Other people who have driven my car have said they think the brakes are fine.
At some point I will replace the brake pads with something better, like the Hawks mentioned by others. But I've gotten used to driving it the way it is, and don't feel an urgent need to upgrade at this time.
good luck
Joel

[rich grsc]

I would remove the adjustable valve, it only reduces pressure to the caliper. Something you don't need obviously.

[Murd]

You mentioned pushrod and pivot point, did you do the manual brake mod to cut and weld the pedal arm shorter to change the ratio?

[Norm B]

Check that the pushrod is straight into the master cylinder. Mine was at an angle and that is why the Whitby adjustable pushrod helped. Its pivot point is straight inline with the rod whereas the donor is offset. If you want the Whitby one you can have it. PM me.

Norm

[Grande]

I have the pedal modification done, 1.5 inches lower, cut pedal and even made the pushrod adjustable.so all good there, I have no proportioning valve like someone state to remove, have the wilwood. So really dissapointed to know I can’t lock wheels up, thought I would be enjoying adjusting front rear bias with valve no way can I keep it like this, strangely some guys say it brakes good, I must be doing something different , keep on giving me advise...thx

[Grande]

So if I decide to go back to booster, which booster is suggested ? I keep the original master? Do I have to place back and original pedal since this one was modified?

[Jeff Kleiner]

So if I decide to go back to booster, which booster is suggested ? I keep the original master? Do I have to place back and original pedal since this one was modified?

Fox booster, 15/16" master from 1995 Mustang SVO Cobra, unmodified pedal.

Jeff

[CraigS]

I have the pedal modification done, 1.5 inches lower, cut pedal and even made the pushrod adjustable.so all good there, I have no proportioning valve like someone state dto remove, have the wilwood. So really dissapointed to know I can’t lock wheels up, thought I would be enjoying adjusting front rear bias with valve no way can I keep it like this, strangely some guys say it b4akes good, I must be doing something different , keep on giving me advise...thx

And you need to hack the frame for it to fit.

[mike223]

Try a 21mm bore master cylinder - no booster.

The one I'm using is from about an 87 Thunderbird - AutoZone p# NM-1907.

Works "perfect" (for me) with SN95 single piston fronts + Thunderbird rear calipers (IRS) + about a 4:1 pedal.

It will be even closer to power brakes with a 6:1 pedal.

If you need the Mustang type MC for the three metric brake line fittings, look for a 21mm MC in the fox body time frame, maybe like this (but double check everything on the fitting sizes):https://lmr.com/item/LRS-2140C/1987-93-Mustang-Brake-Master-Cylinder-For-23L-50L?gclid=Cj0KCQjwnv71BRCOARIsAIkxW9FG5bxRoMOYtNjH mO9TnccHMn9zAh8VFeet9qaSxYsgCqj53dL-UEYaAoDhEALw_wcB




Regarding rear bias - too many variables to give advice over the internet.

You just have to try it and proceed with caution.

You never want the rears locking first in a panic stop.

[Grande]

I had the same brake setup initially minus the the Willwood adjustable valve. I gutted the stock Mustang valve and kept it because it is required for registration where I plan to retire. Brakes were okay but not great. I tried the Whitby adjustable pushrod and that improved things a little. Could have tried different pads to get more improvement but decided to go the power brake route instead.

Very happy with the brakes now. More confident driving the car, most likely due to the fact that the brakes feel the same as our daily drivers.

If you decide to go power brakes you will need the booster for an 87-93 Mustang because the sn95 ones are too big.

HTH

Norm
OK Norm, so I will go that route cause it isnt acceptable, i have valve Wilwood because I thought I would be adjusting brake lock front rear,which doesnt exist. So if I go 87-93 booster route, do I use the original 95 master?, I will have to install a original non modified pedal again,right, is the push road booster side match the brake master,thanks.

[Grande]

Fox booster, 15/16" master from 1995 Mustang SVO Cobra, unmodified pedal.

Jeff

ok, so my 95 GT master is to aggressive with the power setup, if I use booster(FOX) like in original (SN95)GT car?

[Grande]

ok thanks all of you from all the valuable advice, will try to take it all in and see which route should be taken, already new pads(original) installed so I dont think I will buy new replacement aggressive pads, maybe will think about a Fox booster addon, body is coming off for paint soon, so not a big deal, and pedal box will be accessable. Thought after booster addon I could have used original 95 GT master....guess not..

[Jeff Kleiner]

ok, so my 95 GT master is to aggressive with the power setup, if I use booster(FOX) like in original (SN95)GT car?

Actually no, the opposite. You need to understand the fluid dynamics involved; a master cylinder with a smaller bore will create more line (and therefore caliper) pressure at a given application force (note that I said force, not pedal travel) than one with a larger bore. The 1995 GT master has a bore of 1.062" while the Cobra master has a bore of .937". When you perform the math a 100 pound application force will produce a line pressure of approximately 113 psi with the larger bore. That same 100 pound application force will create a line pressure of 145 psi with the Cobra master. In a nutshell, the same pedal/leg pressure at the pedal will produce 28% more clamping pressure at the caliper piston. Understand that the master with the larger diameter piston can produce the same line pressure as the one with a smaller piston but it requires more pedal/leg force to do so. I think this is what you have discovered by using the original 1995 Master without power assist---it becomes difficult if not impossible to apply sufficient force at the pedal to produce enough line pressure to fully engage the calipers. Now on to the second part of the equation...he smaller piston obviously does not move the same volume of fluid as the large one when they are depressed equal distances so the pedal will travel farther when 100 pounds of force are applied. This longer travel however can allow for finer brake modulation through the pedal...this is a bit of an exaggeration but an especially large diameter master cylinder piston will perform kind of like an on/off switch because of the short range of travel between fully released and fully applied. Long story short is yes, the original 1995 GT master cylinder can be used and will work with a booster---but in my experience the 15/16" diameter one works better for our purposes, especially if not boosted.

Good luck,
Jeff

[Grande]

Actually no, the opposite. You need to understand the fluid dynamics involved; a master cylinder with a smaller bore will create more line (and therefore caliper) pressure at a given application force (note that I said force, not pedal travel) than one with a larger bore. The 1995 GT master has a bore of 1.062" while the Cobra master has a bore of .937". When you perform the math a 100 pound application force will produce a line pressure of approximately 113 psi with the larger bore. That same 100 pound application force will create a line pressure of 145 psi with the Cobra master. In a nutshell, the same pedal/leg pressure at the pedal will produce 28% more clamping pressure at the caliper piston. Understand that the master with the larger diameter piston can produce the same line pressure as the one with a smaller piston but it requires more pedal/leg force to do so. I think this is what you have discovered by using the original 1995 Master without power assist---it becomes difficult if not impossible to apply sufficient force at the pedal to produce enough line pressure to fully engage the calipers. Now on to the second part of the equation...he smaller piston obviously does not move the same volume of fluid as the large one when they are depressed equal distances so the pedal will travel farther when 100 pounds of force are applied. This longer travel however can allow for finer brake modulation through the pedal...this is a bit of an exaggeration but an especially large diameter master cylinder piston will perform kind of like an on/off switch because of the short range of travel between fully released and fully applied. Long story short is yes, the original 1995 GT master cylinder can be used and will work with a booster---but in my experience the 15/16" diameter one works better for our purposes, especially if not boosted.

Good luck,
Jeff
Oh my God, picking your brain is always a pleasure. Now that could not have been explained better. I again thank you Jeff, and of course the other gentlemen who make building these cars so much easier. When someone says you built that car, I say we built that car.