Brakes ATS brembos and drums

5ptslow · Nov 16, 2025

ok so the car is a 1979 with a 1990 drivetrain, fuel tank, brakes etc put into the 79

i planned on putting the ATS brembos up front and just switch to the 5 lug drums in the rear...would this combo work? its just a bigger caliper added to the system right?? im upgrading to the cobra booster/mc and all that too.

AeroCoupe · Nov 16, 2025

Brake bias will be all jacked up but it will stop.

5ptslow · Nov 16, 2025

AeroCoupe said:
Brake bias will be all jacked up but it will stop.

how jacked? im hoping no rear brake lockups?

nickyb · Nov 16, 2025

Why not go four wheel.disc?

5ptslow · Nov 16, 2025

nickyb said:
Why not go four wheel.disc?

guess im planning a rear caliper kit

Mustang5L5 · Nov 16, 2025

I’m not even sure what MC to use with that combo to get decent pedal feel.

KRUISR · Nov 16, 2025

You would be far better to just put 99-04 brakes all around with booster and prop valve from same (actually from a non ABS car would be easiest as no mods to prop valve would be needed).

AeroCoupe · Nov 17, 2025

Just a heads up but the 99-04 GT cars don’t have a booster as they moved to hydraboost in 1996. V6 cars still have vacuum boosters.

Mustang5L5 · Nov 17, 2025

They used 1.003" bore MC"s, so a 1993 Cobra MC and booster can be used with the 99-04 setup.

5ptslow · Nov 17, 2025

well its got the cobra mc & booster but im just gonna buy the whole rear kit...easiest.

for s n giggles would putting a adj prop valve to to the rear drums work??

AeroCoupe · Nov 17, 2025

Sure. Gut the stock one and toss the adjustable one in. It will work just fine. Problem is bias will still be dog .

Good read

https://www.brakes-shop.com/brakepedia/general/brake-bias-and-performance?srsltid=AfmBOor0Poo6bFJG1-IMSeJodZOZR9CRZBZ0khqtL8l2jp9bl4dLCCAm

2000xp8 · Nov 20, 2025

Pick a proven setup and do all four corners.
No shortcuts, no saving money (other than on the right parts at cheaper prices), no doing it for looks (which is what 4 piston in the front and drums in the rear sounds like to me).
Do it once and do it right and most likely you will never work on the brakes again.

91GTstroked · Apr 3, 2026

A previous owner did a rear disc brake conversion on my 90 convertible. They didn't even install a proportion valve. The brakes were in bad shape. I replaced everything and added a proportion valve.

I believe the front brakes are still stock original. So I just ordered the complete front brake kit from LMR. But I haven't installed it yet. I may also need to do the 93 cobra brake booster upgrade.

Below is the front brakes I just got.

https://lmr.com/item/SVE-2320BK4S/sve-mustang-svo-style-front-brake-kit-4-lug-stock-87-93

86HO5.0 · Apr 3, 2026

2000xp8 said:
Pick a proven setup and do all four corners.
No shortcuts, no saving money (other than on the right parts at cheaper prices), no doing it for looks (which is what 4 piston in the front and drums in the rear sounds like to me).
Do it once and do it right and most likely you will never work on the brakes again.

Agreed. I went with matching Cobra spec brakes FR and Rear to ensure proper brake bias was never an issue. I've seen and heard of too many people mixing and matching front and rear brake setups only to be disappointed with performance due to insurmountable brake bias issues.

KRUISR · Apr 3, 2026

91GTstroked said:
A previous owner did a rear disc brake conversion on my 90 convertible. They didn't even install a proportion valve. The brakes were in bad shape. I replaced everything and added a proportion valve.

I didn't use an aftermarket prop valve either. I used a factory one from a '01 V6 non-ABS car. They use a single brake line to the rear (just like a foxbody) and have the bias sorted for rear discs already. The only challenge is the threaded fittings are metric vs SAE for stock foxbodies. The solution is when getting the prop valve off a car at the wreckers, take 6" of brake line coming from the prop valve. Now you have all the fittings you need. Easy swap and you don't need to gut your existing unit or add an aftermarket unit for the rear.

91GTstroked · Apr 3, 2026

KRUISR said:
I didn't use an aftermarket prop valve either. I used a factory one from a '01 V6 non-ABS car. They use a single brake line to the rear (just like a foxbody) and have the bias sorted for rear discs already. The only challenge is the threaded fittings are metric vs SAE for stock foxbodies. The solution is when getting the prop valve off a car at the wreckers, take 6" of brake line coming from the prop valve. Now you have all the fittings you need. Easy swap and you don't need to gut your existing unit or add an aftermarket unit for the rear.

Nice . I really don't mind the aftermarket one. It's a Ford Racing one and looks good. Took 10-15 minutes to install.

nickyb · Apr 3, 2026

Its been quit a few years since I've done my five lug,four wheel disc brakes to my93 lx.
I went with a 95 proportioning valve, I gutted it and used the internals in my valve.
I did this because I could not find one single article on how to.correct!y adjust the ford proportioning valve, and since Ford spends a good amount of money for R&D on brake bias I figured the 95 has four wheel.disc and the weight is close enough.

AeroCoupe · Apr 3, 2026

So it’s really easy to adjust. After installation and prior to bleeding the system:
1) Screw the knob on the adjustable proportioning valve all the way in (clockwise)
Once bled or if in an existing and properly functioning brake system:

2) Turn the adjusting screw on the proportioning valve counter clockwise until it stops. Then turn it four turns clockwise for the initial adjustment.

The optimum adjustment will result in the front brakes locking just prior to the rear, under the worst conditions. So think (minimum traction surface and minimum rear wheel load.

3) After a panic stop to dial the brakes in you turn the knob clockwise to increase rear brake pressure and counter-clockwise to decrease it.

That’s all there is to it. The purpose of having the rears lock up before the fronts is to keep the car straight in a panic stop.

Mustang5L5 · Apr 4, 2026

I just keep mine full in (or maybe it was out) for full reduction to the rears.

TBH, unless you guys are racing around a track on the edge of traction, you don’t need to go crazy getting absolutely perfect brake bias, but try to err on the side of less pressure to the rears.

AeroCoupe · Apr 4, 2026

Agreed 100% for most street cars. For me it was that I spent all the money on 11.65" rear brakes so I want all I can get out of them. Only took about an hour dialing them in because I was using 1/4 to 1/2 turn increments.

Brakes ATS brembos and drums

5ptslow

AeroCoupe

lube between the nut and the face. I know my lubes

5ptslow

nickyb

I gotta say i never painted my nuts, Never Ever

5ptslow

Mustang5L5

That is…until I whipped out my Bissell

KRUISR

AeroCoupe

lube between the nut and the face. I know my lubes

Mustang5L5

That is…until I whipped out my Bissell

5ptslow

AeroCoupe

lube between the nut and the face. I know my lubes

2000xp8

91GTstroked

86HO5.0

Active Member

KRUISR

91GTstroked

nickyb

I gotta say i never painted my nuts, Never Ever

AeroCoupe

lube between the nut and the face. I know my lubes

Mustang5L5

That is…until I whipped out my Bissell

AeroCoupe

lube between the nut and the face. I know my lubes

Similar threads

Brakes ATS brembos and drums

lube between the nut and the face. I know my lubes

I gotta say i never painted my nuts, Never Ever

That is…until I whipped out my Bissell

lube between the nut and the face. I know my lubes

That is…until I whipped out my Bissell

lube between the nut and the face. I know my lubes

Active Member

I gotta say i never painted my nuts, Never Ever

lube between the nut and the face. I know my lubes

That is…until I whipped out my Bissell

lube between the nut and the face. I know my lubes

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