Brakes The Ultimate 4-lug/5-lug Brake Conversion/upgrade Thread

Mustang5L5 · Dec 21, 2024

86VertFinland said:
Hi! You had good info on swapping sn95 brakes to
79-86 fox. I have one stupid question.. i already have swapped 11” brakes and spindles from 1996 Mustang to my -86. Its still on 5-lug drums rear and master cylinder is original.
I just bought rear disc kit from foxbodybrakes.com (sn95 10.25”) eith one piston GT calibers like i have in front.
Does my original master cylinder work with these? I also bought new proportioning valve.. Or do i need a mc from svo, 1985 town car or 1993 cobra? I am confused..

Thanks in advance if you would be so kind to help..

No, you would need to change the master cylinder with any rear disk conversion.

Sounds like you are doing GT rear brakes. With that said 94-98 Mustang GTs are the single piston 66mm caliper up front and the 94-95 cars and 94-98 v6 cars use a 1 1/16” bore MC.

You’d want to run a 94-95 GT master cylinder and you’ll need this adapter kit

Master Cylinder Installation Kit, 1993 Cobra/1994-95 GT m/c in 1980-86 Mustang

You will also want to gut the stock combo valve and install an adjustable valve. You may be able to find them cheaper elsewhere but here is one stop shopping

1-1/16" 1994-95 GT master cyl.

You may find you want to upgrade the booster. You can either try the 87-93 GT booster if you like a firmer pedal, or a 1993 cobra booster. Or you can try it as is and see how you like it. But if your initial thought is too much pedal effort, you’ll want to consider the booster swap as well

Good luck

Willybill32 · Dec 21, 2024

86VertFinland said:
Hi! You had good info on swapping sn95 brakes to
79-86 fox. I have one stupid question.. i already have swapped 11” brakes and spindles from 1996 Mustang to my -86. Its still on 5-lug drums rear and master cylinder is original.
I just bought rear disc kit from foxbodybrakes.com (sn95 10.25”) eith one piston GT calibers like i have in front.
Does my original master cylinder work with these? I also bought new proportioning valve.. Or do i need a mc from svo, 1985 town car or 1993 cobra? I am confused..

Thanks in advance if you would be so kind to help..

I put '87-'93 front brakes on my '86 for the larger rotors, then did the SSBC rear disc kit. SSBC's instructions said I could use the original '86 master cylinder, but required gutting the stock proportioning valve and adding a discrete proportioning valve. But once everything was done, I was dissatisfied with that arrangement and bought an '85/'86 Lincoln master cylinder, as it looked pretty much like the original, but with larger bore. My '86 has recently been redone, and the decision was made to replace the original booster with a '93 Cobra booster and master cylinder. As it turns out, getting the '93 Cobra booster into the '86 was a real chore...

Bill

86VertFinland · Dec 21, 2024

Mustang5L5 said:
No, you would need to change the master cylinder with any rear disk conversion.

Sounds like you are doing GT rear brakes. With that said 94-98 Mustang GTs are the single piston 66mm caliper up front and the 94-95 cars and 94-98 v6 cars use a 1 1/16” bore MC.

You’d want to run a 94-95 GT master cylinder and you’ll need this adapter kit

Master Cylinder Installation Kit, 1993 Cobra/1994-95 GT m/c in 1980-86 Mustang

You will also want to gut the stock combo valve and install an adjustable valve. You may be able to find them cheaper elsewhere but here is one stop shopping

1-1/16" 1994-95 GT master cyl.

You may find you want to upgrade the booster. You can either try the 87-93 GT booster if you like a firmer pedal, or a 1993 cobra booster. Or you can try it as is and see how you like it. But if your initial thought is too much pedal effort, you’ll want to consider the booster swap as well

Good luck

Thank you so much! So the 3-port system from sn95 will fit this 2-port system with this adapter from maximum motorsport? Sorry, i am not good on brakes.. I ask because i read from lmr.com that the only one that fits this car is svo mc..
And will a 1993 cobra booster fit in place? It has so little room..

Yours, Marko

KRUISR · Dec 21, 2024

I used a proportioning valve from an SN95 non ABS car. The non ABS cars used a single brake line to the rear (just like a foxbody) and had rear discs so the proportioning aspect should be good. For so far no issues. I will be doing this again with my son's 89 GT as we build it (I have a stash of non ABS prop valves).

Only thing you need to do is swap the brake line fittings at the prop valve as SN's use a different thread. Its not a big deal if you pull the prop valve from a wreckers as you can take a 4-6" section of brake line with it (then you have the fittings you need). Then you just cut the end off your stock brake lines and add the new fitting and re-flare the line.

Mustang5L5 · Dec 21, 2024

86VertFinland said:
Thank you so much! So the 3-port system from sn95 will fit this 2-port system with this adapter from maximum motorsport? Sorry, i am not good on brakes.. I ask because i read from lmr.com that the only one that fits this car is svo mc..
And will a 1993 cobra booster fit in place? It has so little room..

Yours, Marko

SN95 master cylinder is 2-port, just like the 79-86 mustangs. So you only need the adapter lines to change between the two for Maximum Motorsports

LMR is partially correct. Typically for the older cars the SVO 1 1/8” MC and the Lincoln town car 1” MC are what are typically used, however they probably don’t know Max Motorsports now sells the adapter kits for the 2-port modern metric MCs

jaygee15 · Jan 6, 2025

Mustang5L5 said:
Or you use 1" bore 1985 Lincoln town car MC and a couple Autozobe adapters.

1986 Mustang master cylinder swap - Ford Mustang Forums : Corral.net Mustang Forum

The SVO mc is just not ideal for his combo despite being the easiest to install. Just cuz it's easy doesn't mean it's right.

Fortunately...there are a few ways to do this. Above is one

Sent from my big ass iPhone 6 using Tapatalk

sorry to bring up this really old comment, but I am trying to design my budget brake upgrade for my 86 6 cylinder fox body that I will be v8 swapping as well as upgrading all suspension, brakes, rear end etc. i am building this car on as low a budget as possible while still getting quality improvement upgrades. From my research, I am planning on doing sn95 swap for front rotor,spindle, caliper, and doing the whole rear end with brakes for disc and 5 lug swap. Concerning the MC and BB, would this MC from towncar be a good fit for this setup? What would be a proper BB and proportioning valve with this setup, would I have to do the gutted proportioning valve thing? Would this be the best, easiest swap for this setup. Thanks for any help from anyone who can answer .

limp · Jan 6, 2025

jaygee15 said:
sorry to bring up this really old comment, but I am trying to design my budget brake upgrade for my 86 6 cylinder fox body that I will be v8 swapping as well as upgrading all suspension, brakes, rear end etc. i am building this car on as low a budget as possible while still getting quality improvement upgrades. From my research, I am planning on doing sn95 swap for front rotor,spindle, caliper, and doing the whole rear end with brakes for disc and 5 lug swap. Concerning the MC and BB, would this MC from towncar be a good fit for this setup? What would be a proper BB and proportioning valve with this setup, would I have to do the gutted proportioning valve thing? Would this be the best, easiest swap for this setup. Thanks for any help from anyone who can answer .

Start looking now for the sn94/95 spindles... If your local wrecking yards show cars online look a couple of times a week for a 94-95 car.... Much better deals on them there than buying them from any parts flipping whors.....
I paid around $70 for both sides....

Willybill32 · Jan 6, 2025

jaygee15 said:
sorry to bring up this really old comment, but I am trying to design my budget brake upgrade for my 86 6 cylinder fox body that I will be v8 swapping as well as upgrading all suspension, brakes, rear end etc. i am building this car on as low a budget as possible while still getting quality improvement upgrades. From my research, I am planning on doing sn95 swap for front rotor,spindle, caliper, and doing the whole rear end with brakes for disc and 5 lug swap. Concerning the MC and BB, would this MC from towncar be a good fit for this setup? What would be a proper BB and proportioning valve with this setup, would I have to do the gutted proportioning valve thing? Would this be the best, easiest swap for this setup. Thanks for any help from anyone who can answer .

I'm sure @Mustang5L5 will provide a good answer, but thought I'd share my experience. I added the SSBC rear disc conversion to my '86 GT. Their instructions said I could keep the stock '86 master cylinder, but had to gut the stock proportioning valve and add a manual proportioning valve, both of which I did. I did not like the brake feel with the stock '86 MC, so I upgraded to the larger bore Lincoln master cylinder. It worked OK. I recently had some work done on the car and decided that the stock booster was 38 years old and made the decision to replace the booster and master cylinder with the '93 Cobra parts. Maximum Motorsports sells a kit with the necessary lines to plumb up the new master cylinder. I think I used the manual Ford proportioning valve from LMR.com. Just a warning...getting the new booster on was a difficult task, since the '86 shock tower doesn't have an indentation like the newer Fox body cars.

Bill

jaygee15 · Jan 6, 2025

limp said:
Start looking now for the sn94/95 spindles... If your local wrecking yards show cars online look a couple of times a week for a 94-95 car.... Much better deals on them there than buying them from any parts flipping whors.....
I paid around $70 for both sides....

thank you.

Willybill32 said:
I'm sure @Mustang5L5 will provide a good answer, but thought I'd share my experience. I added the SSBC rear disc conversion to my '86 GT. Their instructions said I could keep the stock '86 master cylinder, but had to gut the stock proportioning valve and add a manual proportioning valve, both of which I did. I did not like the brake feel with the stock '86 MC, so I upgraded to the larger bore Lincoln master cylinder. It worked OK. I recently had some work done on the car and decided that the stock booster was 38 years old and made the decision to replace the booster and master cylinder with the '93 Cobra parts. Maximum Motorsports sells a kit with the necessary lines to plumb up the new master cylinder. I think I used the manual Ford proportioning valve from LMR.com. Just a warning...getting the new booster on was a difficult task, since the '86 shock tower doesn't have an indentation like the newer Fox body cars.

Bill

Yes ,thats why i was considering the lincoln thing, I know with certain BB you have to alter the factory holes and "massage" the tower, which I'd rather not have to do. Thanks for the info.

Rdub6 · Jan 6, 2025

On my ‘86 I used the PBR dual pistons in the front, and ‘94-‘04 rear calipers. I used a Ford 1” master cylinder with the original booster. Can be positive, but was probably the Lincoln m/c. It bolted right up to the lines, and looked just like the original (no plastic reservoir). I’m pretty happy with the feel of the brakes.

Blackhawkxx · Jan 6, 2025

I'm new to this thread but had to laugh after looking how many pages there were.

Mustang5L5 said:
I don't want this to turn into a 21-page thread where someone can't find the info they need.

Noobz347 · Jan 6, 2025

Blackhawkxx said:
I'm new to this thread but had to laugh after looking how many pages there were.

Can't argue with success.

Mustang5L5 · Jan 6, 2025

jaygee15 said:
sorry to bring up this really old comment, but I am trying to design my budget brake upgrade for my 86 6 cylinder fox body that I will be v8 swapping as well as upgrading all suspension, brakes, rear end etc. i am building this car on as low a budget as possible while still getting quality improvement upgrades. From my research, I am planning on doing sn95 swap for front rotor,spindle, caliper, and doing the whole rear end with brakes for disc and 5 lug swap. Concerning the MC and BB, would this MC from towncar be a good fit for this setup? What would be a proper BB and proportioning valve with this setup, would I have to do the gutted proportioning valve thing? Would this be the best, easiest swap for this setup. Thanks for any help from anyone who can answer .

To answer this question properly need to identify which front SN95 brakes you are using.

85 town car MC is a 1" bore MC. So with the standard SN95 rear 38mm pistons, you could use that bore with:

99-04 GT 2-piston PBR's
99-04 Cobra PBRs

If you are using the 94-98 cobra calipers or 94-98 GT single piston calipers, there are different MC's i would recommend instead.

BTW the 85 town car and 93 cobra MC are both 1" bore MC's so if you prefer the modern plastic reservoir look you can use that plus the adapter kit i linked in post #401

Mustang5L5 · Jan 6, 2025

Noobz347 said:
Can't argue with success.

Actually i made this new thread. A little bit more cleaned up

Thread 'Ultimate 5-lug swap thread - new/updated'

Jul 21, 2022

This thread is a work in progress. I've unlocked the thread for feedback and questions and if i've missed something or need to correct. I'm still adding/editing.

Wanted to make a new thread to replace the old thread which has info scattered around in many posts. Hoping to consolidate this down and make it more simple. Please limit this thread to discussion on the 5-lug swap, and any issues due to the swap, and not mechanical issues concerning brakes.

Table of Contents

Post#/Topic

General Overview/contents (this post)
Fox spindle 5-lug swap rotors...

jaygee15 · Jan 7, 2025

Mustang5L5 said:
To answer this question properly need to identify which front SN95 brakes you are using.

85 town car MC is a 1" bore MC. So with the standard SN95 rear 38mm pistons, you could use that bore with:

99-04 GT 2-piston PBR's
99-04 Cobra PBRs

If you are using the 94-98 cobra calipers or 94-98 GT single piston calipers, there are different MC's i would recommend instead.

BTW the 85 town car and 93 cobra MC are both 1" bore MC's so if you prefer the modern plastic reservoir look you can use that plus the adapter kit i linked in post #401

I am new to fox body as of about 4 months ago. From my research and understanding, I am planning to use 94-95 spindles as recommended. From the same research I was originally planning doing the Cadillac ATS brembo calipers, but given the limited wheel fitment and the wheels I want to run, I have decided against that. My second choice was going to be 94-94 calipers, brackets, master cylinder and a cobra booster from my notes i wrote myself. Once I discovered this thread, I see there may be other options for the master cylinder and brake booster , that may cost less, easier fitting(direct bolt in with no massaging of tower or drilling of existing brake booster holes). My goal is simply to have better brakes, dont have to be the best, easy swap, and low budget. I have not bought anything as of yet, just planning my build, only thing i own is the car.

limp · Jan 8, 2025

jaygee15 said:
I am new to fox body as of about 4 months ago. From my research and understanding, I am planning to use 94-95 spindles as recommended. From the same research I was originally planning doing the Cadillac ATS brembo calipers, but given the limited wheel fitment and the wheels I want to run, I have decided against that. My second choice was going to be 94-94 calipers, brackets, master cylinder and a cobra booster from my notes i wrote myself. Once I discovered this thread, I see there may be other options for the master cylinder and brake booster , that may cost less, easier fitting(direct bolt in with no massaging of tower or drilling of existing brake booster holes). My goal is simply to have better brakes, dont have to be the best, easy swap, and low budget. I have not bought anything as of yet, just planning my build, only thing i own is the car.

I was in your position a few years ago with an " inherited" fox body after a diet of Chevelles, Camaro's and corvettes when i was younger...
Lots of good people on here helped me out....
I read up on the Aerostar and Ranger axle and rotor change out steps etc.... Ended up with 94-95 spindles and newer front rotors and brakes from a 99-04 car.. I exchanged my flat pancake style booster for the smaller one ( not the cobra)....
Check the fitting of the calipers on the front brackets as they can just barely touch and you need to take a little material off the bracket..

AeroCoupe · Jan 8, 2025

The 93 Cobra booster has the same bolt pattern as the stock booster. Having to dimple the rear of the shock tower seems to be hit or miss and if you have the motor out its super easy. Running the stock booster with the Cobra MC is hit or miss as well depending on your personal taste with regards to pedal effort. I would just say this, Ford designed the SN95 style brakes to come with the brake booster and master cylinder that came on those cars so its a good idea to just use what they put a lot of R&D into. I have done a few of these conversion with the 93 Cobra booster and 93 MC as well as the 94/95 booster and 94/95 MC with either the GT/V6 brakes or the Cobra setups and all of them turned out really well with excellent braking compared to the abomination of a brake system the Foxes have.

Both of my current Foxes have SN95 Cobra brakes on them with the Coupe being the test mule that went from 4 cylinder brakes to Fox V8 brakes to then swapping the front calipers to the larger SVO/Lincoln units, to the SN95 GT/V6 brakes, and finally to the full SN95 Cobra brakes. I can tell you it was all a waste of money and I should have just moved to straight to the SN95 brakes and been done with it. I will say that really the only reason to go to the Cobra setup is for the bling behind the wheels or if you are really going to utilize them for some occasional road racing etc. If you are going to put some serious seat time on the track then run the Cobra rears and move up to the StopTech front brakes or a full Griggs Racing Sierra brake system and be done with it.

jaygee15 · Jan 8, 2025

@limp Thanks for the info. I had always been a fox body fan, but never got around to owning one until recently. One of my cars I've always wanted to own. luckily I have check a few cars off my list. Currently I also own my frame off build 64 impala.

@AeroCoupe Thank you, So I could just run 94-95 complete brake system from any 94-95 (front spindles,rotors, calipers, mc, bb, complete Rear end with fox length axle shafts) and that be a great upgrade to the car? If its as simple as you say I wouldnt mind dimpling the tower and just being an easy straight forward budget swap. Thats exactly what I'm looking for.

jaygee15 · Jan 8, 2025

I've seen mentions of the sn95 rear end(94-95 i believe) and that there are two types when it comes to the brake line/hardline/softline, and that one is much easier to swap to a fox body. Does anyone have info on this, specs, pics of differences ?

Noobz347 · Jan 8, 2025

jaygee15 said:
I've seen mentions of the sn95 rear end(94-95 i believe) and that there are two types when it comes to the brake line/hardline/softline, and that one is much easier to swap to a fox body. Does anyone have info on this, specs, pics of differences ?

I don't personally, recommend this route. Do the conversion to a Fox length axle housing. An SN95 axle on a Fox creates more issues than it solves IMO.

For the brakes:

Mustang Rear Disk Brake Caliper Adapter Brackets For 94-04 GT/V6 Calipers (79-93)

Check out these rear brake adapter brackets for your 79-93 Mustang Foxbody! Install 94-04 Gt/V6 Calipers

lmr.com

You will also need to order a set of axles.

I'd also choose this time to upgrade to a 31-spline F-150 Trac-Lok, but that's just me.

Brakes The Ultimate 4-lug/5-lug Brake Conversion/upgrade Thread

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