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Discussion Starter #1
I wanted to document for others the FTR "Working Man's Big Brake Kit" conversion from stock 11" to 14" Boss/GT500 rotors and drum brakes to rear disc. I wasn't able to find anyone do this on a foxbody yet, so i wasn't sure on some of the fitment issues that I would run into. I thought everyone would enjoy this for future projects.

Old Stock Combo:

FRONT
- Stock GT 11" front drilled/slotted rotors
- Stock GT single 60mm piston calipers
- Koni Orange SRT-T Struts
- MM 87-93 stainless steel brake lines
- Eiback Pro Springs
- Hawk HPS brake pads
- Stock spindles
- Stock balljoints

BACK
- Stock drum brakes
- Koni Orange SRT-T Shocks
- Eiback Pro Springs

New Combo:

FRONT
- Boss/GT500 14" drilled/slotted/cryo treated rotors
- Stock S197 GT twin 43mm piston calipers & bracket
- FTR SN95 14" S197 Retrofit Brake Kit bracket
- 94/95 Front Spindles
- MM 87-93 stainless steel brake lines (Reused)
- Stock balljoints (Reused with washers/spacer)
- Koni Yellow Struts
- MM front coilover with 350lb springs

BACK
- 98 GT rearend with disc brakes
- Koni Yellow Shocks

WHEEL/TIRES
- AMR 18" Drift Wheels
- Cooper Zeon RS3-A 245/40/18 Tires

MASTER CYLINDER/PROPORTIONING VALVE
- Ford Racing PP Valve
- 50Resto PP Valve Plug

Start of the Project:
IMG_20160415_202441875.jpg
IMG_20160415_203023401_HDR.jpg
IMG_20160415_203035236.jpg
IMG_20160415_214842247.jpg
 

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Discussion Starter #4
Test fitting to wheel:
IMG_20160403_141708064.jpg

There was some issues with this part. The top of the S197 GT Caliper needed to be ground down to fit in the wheel. There is a mountain type shape on the top that has to be removed and flatten. After, many test fitting attempts I was able to get everything to fit correctly.

Final fitting:
IMG_20160409_083318736.jpg

Assembly of the MM Coilovers:

IMG_20160407_192810541.jpg
IMG_20160408_103920203.jpg

This is pretty straight forward since MM installations are awesome.
 

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Discussion Starter #5
Installation on car:

I installed the coilover assembly first with the top nut just hand tightened. Then installed the spindle assembly as a whole mounting it to the balljoint and strut.

IMG_20160416_092201850.jpg
IMG_20160416_092213312.jpg

I installed 3 flat washers that I got from tractor supply with a thickness of .33, so the balljoint nut could be tightened down and cotter pin installed. Then reinstalled the endlinks and outer tierod.

Brake Line Adjustment:

As seen in the above pictures the brake lines were not going to fit at full lock. Since the hard line mount needed to be moved anyways for the MM coilover kit I was able to reuse the MM 87-93 Brake Lines.

Moved Driver Side 2":
IMG_20160416_103537864.jpg
IMG_20160416_103603148.jpg

Moved Passenger Side 3":
IMG_20160416_110647262.jpg
 

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Discussion Starter #6
Completed Install:
IMG_20160416_243507400.jpg
IMG_20160416_243514652.jpg
IMG_20160416_114107366.jpg

I set the ride height to 25.5" to give run between the fender and wheel. Since I was using a 05-09 offset wheels it pushes the wheel out further then the stock 87-93.

Under Hood Installation:

Installing
- Ford Racing PP Valve
- 50Resto PP Valve Plug

This was one of the easiest parts of the install since after talking the Jack Hidley at MM we were able to determine that I didnt need to replace the stock 87-93 GT Master cylinder. I just removed the stock PP Valve Plug, and removed its guts. Then removed the O-ring from the old plug and installed it on the new plug. Finally, installed the plug in the PP valve. DONE

I know this is everywhere on the installation of the PP Valve, but I took the time to do a "clean" install. I removed the connector on the passenger side of the car. Then cut the brake line 2" or so, reflared the line, and installed the PP Valve rather than bending all the lines.

IMG_20160417_175204258.jpg
 

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Discussion Starter #7
Final Pictures:
IMG_20160417_175026208.jpg
IMG_20160417_175050020.jpg
IMG_20160417_175008455.jpg

First Drive:

The drive was awesome!!!! Going from stock brakes to this is crazy as the car stops on a dime. I haven't needed to push the brakes any harder then half way as it just stops. After I put a couple miles on it I will be testing the stopping power even more.
 

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I wonder how they compare to the 03/04 13inch cobra brakes. We should get some people to do some side by side testing.
 

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With a 14" rotor and twin 43mm piston caliper, 10.5" rear with 38mm single caliper, I get F/R torque bias at about 81/19. Even if you went up to the Cobra rear rotor bias only moves a little to 77/23 - which is better. That is way too much on the front. Should be around 70/30 or less depending on suspension and tires.
 

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can i ask how you came up with those numbers?

why does it have to be 70/30 or less?
 

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can i ask how you came up with those numbers?

why does it have to be 70/30 or less?
Used a calculator that takes into account rotor size, piston size and count, pressure, friction material, etc. Generally, I hold some of the factors at preset since in most cases those are standard values.

On a Mustang (Fox; sn95) we all know the car is front heavy. It's very hard to get close to a 50/50 weight balance. With this in mind, Ford set F/R brake torque bias to about 70/30 given weight, anti-dive, wheelbase, friction material, etc. and used the brakes systems with which we are familiar. After market designers have played with this ratio and believe the Ford engineers got it right. But, when you mod the suspension and change other factors (e.g., move weight around; alter wheel base) then one can get perhaps a bit more from the rear brake - maybe a 68/32 ratio or better.

Remember, the tires stop the car; the brakes facilitate this. We want all four tire's fiction patches working at maximum. With a 70/30 torque bias we get near that perfect point without overworking or overpowering one end of the car, and our stopping distances improve. You can see that with an 80/20 torque bias, the front is doing all the work and likely will overpower the front traction long before the rears begin helping. This means longer and less optimal stopping distances.
 

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Test fitting to wheel:
View attachment 687849

There was some issues with this part. The top of the S197 GT Caliper needed to be ground down to fit in the wheel. There is a mountain type shape on the top that has to be removed and flatten. After, many test fitting attempts I was able to get everything to fit correctly.

Final fitting:
View attachment 687857

Assembly of the MM Coilovers:

View attachment 687865
View attachment 687873

This is pretty straight forward since MM installations are awesome.
I was going the exact same route you have taken but on my SN-95. I was debating on the 19" wheels, when I found a FTBR 14" brembo brake conversion kit that
fits 18s...
 

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thank you fir the great info!

what would be the ideal or logical upgrade to the fronts while keeping the cobra rears (this is a fox notch)?

Used a calculator that takes into account rotor size, piston size and count, pressure, friction material, etc. Generally, I hold some of the factors at preset since in most cases those are standard values.

On a Mustang (Fox; sn95) we all know the car is front heavy. It's very hard to get close to a 50/50 weight balance. With this in mind, Ford set F/R brake torque bias to about 70/30 given weight, anti-dive, wheelbase, friction material, etc. and used the brakes systems with which we are familiar. After market designers have played with this ratio and believe the Ford engineers got it right. But, when you mod the suspension and change other factors (e.g., move weight around; alter wheel base) then one can get perhaps a bit more from the rear brake - maybe a 68/32 ratio or better.

Remember, the tires stop the car; the brakes facilitate this. We want all four tire's fiction patches working at maximum. With a 70/30 torque bias we get near that perfect point without overworking or overpowering one end of the car, and our stopping distances improve. You can see that with an 80/20 torque bias, the front is doing all the work and likely will overpower the front traction long before the rears begin helping. This means longer and less optimal stopping distances.
 

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thank you fir the great info!

what would be the ideal or logical upgrade to the fronts while keeping the cobra rears (this is a fox notch)?
Other than the standard Cobra PBRs? Well, the 2000R Brembo was designed with the rear Cobra brakes in mind. Torque bias is the same as with the 2-pot PBR. StopTech makes a 4-pot as well as a 6-pot designed for Fox and sn95 cars with the rear Cobras. I opted for the ST40 (4-pot) 14" rotor for my 86 which yields about 69/31 torque bias. Others, such as Wilwood, Baer, Brake Man, etc. would need to publish the piston sizes and then run through the calculator to see what is optimal. Or trust the vendor (there are some that take this stuff seriously and put packages together specifically for a particular system).

One can also alter the F/R bias with different friction material (not advised); a larger rotor and/or larger rear caliper (meaning total piston area); of course smaller front rotor/caliper. The mistaken idea is that all of this can be adjusted with the prop valve - it can't; not designed for that.
 

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Wouldn't the ratio change if it has a torque arm? What is the proportioning valve doing if it is not adjusting the bias?


Sent from AutoGuide.com Free App
 

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Wouldn't the ratio change if it has a torque arm? What is the proportioning valve doing if it is not adjusting the bias?
I believe there is some impact when using a T/A, or the Steeda 5-link and/or moving weight around. But these differences are not included in the calculator I use. Perhaps a more sophisticated version would. But for general comparison purposes, the torque bias calculator gets the user very close.

The adjustable prop valve adjusts knee-point bias. This is for panic stop type situations. The pressure slope to the rear wheels is linear when used in normal driving. But when you hit the brakes hard, if the slope stayed linear most likey you would lock the rears before the fronts - due to weight transfer, rear jacking, etc. This is bad since the rear generally wants to come around. The prop valve (factory or manual) is designed to reduce pressure to prevent rear lock before front lock. It does this by changing the pressure slope at a preset point - it looks like a knee - hence knee-point - the point on the slope where the pressure changes.

Factory prop valves are pre-set based upon all the factors previously discussed. The manual prop valve moves the knee-point up/down the slope depending on driver preference given friction material, tires, suspension, etc. Torque bias is not affected by the prop valve; torque bias is a brake system design issue.
 

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thanks qtrracer
 

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Discussion Starter #19
Very cool. I didn't know this kit existed till now. Do you have to run a S197 offset wheel? The FTR site doesn't say.
I dont believe so

I just did to push the wheel out a little more and to compensate for the 94-98 rearend I was using due to the increased width.
 

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^^^^ I think you mean to pull the wheels in a little to account for the wider rear axle. Typically S197 wheels have more offset than Fox/SN95 wheels, so they work well with the SN95 rear on a Fox.
 
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