I can't. I never have.


I am having a hard time making sense of my brakes. I've tried multiple combinations and no matter what I do or try, I can't get them to skid on dry pavement.
I'm not a trained mechanic but I do have years of experience with these machines. One method that I use is the process of elimination. If the system has faults and you change enough parts, eventually you will find the problem. This is not easy on the wallet but sometimes it is the only course of action you have to work with.



This car stops well but it isn't awe inspiring. I never feel like I need to lift from the brake pedal because I am about to skid or stopping faster than I want. I have good parts in the car but something just isn't right.
Originally, it was a 4 wheel 10" drum system. You all know how those perform.
My first change was an A body power booster and 11" front discs. It stopped well and never had me feeling like I was scared to drive it fast.
Later, I upsized to the Cordoba 11.75" front rotors.
In 2006 I pulled the rear drums and installed the Dr Diff 11.7" rear disc brakes. From this point forward, the car got faster but the braking stayed the same.
Last year when I had the engine out, I decided to upgrade the brakes. I installed the Dr Diff 13" front kit and went down the rabbit hole in a failed Hydroboost swap. That resulted in a complete failure either due to a faulty HB unit or my impatience in the bleeding procedure. Regardless, the HB came back out and I tried a manual 1 1/8" master cylinder. TERRIBLE. Hard pedal with horrible stopping force. I tried a 15/16" MC. Better, but still not nearly good enough to be content with it.
I put the A body booster back in along with a vacuum pump and tank and that is where I am today.
It stops good enough but I'm still wondering why it won't skid. To me, it seems like if it can't skid, then the system isn't at it's potential.
I bought a brake caliper gauge....

I only measured the rear and it registered 1200 psi.
I'm open to any and all suggestions except swapping drums back on the rear. There is something wrong with the system and I just am not seeing it.
Can you skid on dry pavement?

Here are a few combinations that I've tried:
11" front disc 2.6" caliper, 10" rear drum. 1975 A body brake booster. Disc/drum proportioning valve.
12" front rotor, 2.6" caliper, 10" drum. 1975 A body brake booster. Disc/drum proportioning valve.
12" front rotor, 2.6" caliper, 11.7" Dr Diff rear discs with 1.5" single piston caliper. 1975 A body brake booster. Disc/drum proportioning valve.
12" front rotor, 2.75" caliper, carbon metallic pads. 11.7" rootr with 1.5" single piston caliper. 1975 A body brake booster. Disc/drum proportioning valve.
Same as above without booster but with 15/16" iron, 15/16" aluminum, 1 1/16" and 1 1/8" manual master cylinder. Disc/drum proportioning valve.
12" front rotor, 2.75" caliper, 11.7" rear rotor, 1.5" single piston caliper, drum drum distribution block, 1975 A body brake booster, modified pedal for increased leverage.
13" front rotor, twin 1.58" piston calipers, 11.7" rear rotor, single 1.5" caliper, drum-drum distribution block. Hydroboost unit with 1 1/8" master cylinder.
13" front rotor, twin 1.58" piston calipers, 11.7" rear rotor, single 1.5" caliper, drum-drum distribution block. 1 1/8" manual MC.
13" front rotor, twin 1.58" piston calipers, 11.7" rear rotor, single 1.5" caliper, drum-drum distribution block. 15/16" manual MC.
13" front rotor, twin 1.58" piston calipers, 11.7" rear rotor, single 1.5" caliper, drum-drum distribution block. 1975 A body booster, 1 1/8" MC.
13" front rotor, twin 1.58" piston calipers, 11.7" rear rotor, single 1.5" caliper, drum-drum distribution block. 1975 A body booster, 15/16" MC.
13" front rotor, twin 1.58" piston calipers, 11.7" rear rotor, single 1.5" caliper, drum-drum distribution block. 1975 A body booster, 15/16" MC, electric vacuum pump.
Now the current setup is:
13" front rotor, twin 1.58" piston calipers, 11.7" rear rotor, single 1.5" caliper, drum-drum distribution block. 1975 A body booster, 15/16" MC, electric vacuum pump and storage tank.

Yeah....I have tried LOTS of combinations.

Since the front brakes provide the majority of the braking you need those pressure numbers too.

Let's just focus on what you have right now, the other combos will just confuse the issue. Get the PSI readings at ALL FOUR corners, then let's go from there.

I have Brembo 4 piston calipers on 13” rotors in front and Dr. Diff 11.7” in back. 15/16” master cylinder with no booster and I’m reusing the 4 wheel drum distribution block.

For the first 10 years? with this setup I never locked em up but I never tried (Edit-> except autocross.) The pedal effort is pretty high so I figured that was why I never locked up. Middle of this summer I put new carbon metallic pads on, first auto cross afterwards I burned two flat spots onto my front right tire

just out of curiosity, what is your brake pedal ratio ?

Pedal ratio is an interesting topic.
There is a lot of incorrect info out there so I'll do my best to be clear on how I arrived at my number.
When I measured my pedal, I checked the distance from the center of the pad to the end (from which it swings), then I measured from the pushrod hole to the end. I divided the two. I came up with approx 7 to 1.
This is when I'm directly attached to a manual master cylinder.
The A body power brake booster has reduction linkage built into it that I have not calculated.
I have some things to test just to gather more information. I want to measure caliper pressure at all four corners.
I am considering trying a gutted distribution block to see if it allows more volume and pressure to flow. I'll measure caliper pressure afterwards for comparison purposes.
I intend to weigh my wheels and tires as well as some stock steel wheels like what I have on my other Charger.
The parking brake ....I want to see if it generates enough force to lock the rear wheels from 20 mph, give or take. (Parking lot, of course)

It was a 4 wheel manual drum brake car. I installed a rebuilt 4 speed pedal assembly, should be the factory pedal ratio

I had the car aligned on Tuesday. I asked the man to aim for the maximum caster that he could get, .75 NEG camber and 1/8" toe IN.
Would you believe......
He was able to get 5 degrees of caster on the left, 5.5 on the right?
Yeah....stock UCAs with Moog offset bushings. That is it. I've seen others struggle to get 2 degrees of caster even with these bushings. I don't know of anyone else that has been able to get this much caster without using aftermarket control arms. If so, I'd love to hear about it.
With the front end tracking straight, hard stops seem pretty damn good. It still won't skid but it stops straight and quick.
I may just settle for what I have now and maybe revisit this topic later if need be.

Can you lock up the brakes on wet pavement? If so, which wheel or wheels lock first?

I try to avoid driving in the rain but when I first got the car up and running, I did run it up and down my neighborhood. Some roads had wet patches. Only the front wheels have skidded and even then, it wasn't much.
I slightly skidded the RF on a right turn. The LF skidded when I passed through a damp section.
It actually stops well but won't skid.
With the 13" front brakes, I can't just slip on some of my 15" wheels to test the brakes. I need a 16" minimum to clear the calipers. 15s clear the rear brakes.
I did think of slipping on some skinny tires. I have a pair of 16x7 steelies but they are modified police car wheels. I am not sure that they would clear.

Looks like Mustang calipers on the rear. Make sure they are adjusted for minimum pad clearance.

I can't identify the front calipers, is there an OEM application?

I'd look up master cylinder bores for the donor vehicles and just as important the stroke of the cylinder.

You may be running out of pedal travel before reaching high enough pressure. And 1200 sounds low to me.

This right here, plus you have to regularly use the parking brake to keep them adjusted. Any slop in the rear pad to rotor clearance will affect over all braking performance.

I've had multiple issues with the Cobra calipers on the rear of my Coronet. I've had to replace the calipers a couple of times when they fail to work properly. Not sure why I've had such bad luck with them, they seem to work fine in an OEM application. But when they get out of adjustment they will really reduce braking ability.

i was also under the impression you need to use the parking brake to keep the calipers adjusted when using ford calipers on the rear.
and as was already mentioned, check to be sure you are getting the full travel needed with your brake pedal, and it's not hitting something under the dash causing it to stop before it reaches the travel necessary to fully use the master cylinder stroke.

Just to point out, there's a few things that might prevent fully travel. Linkage binding or hitting something, the booster might not have correct travel, and even the master cylinder can bottom out before reaching high enough pressure.

Disregarding pedal pressure, has this been run as a manual setup? Were the brakes able to lock up then?

Note, the Mustang calipers are different from the Explorer ones. No parking brake in those.

Interesting, my Mustang had parking brakes in the rear caliper, guess it depends on exactly what year Mustang we are talking about. Blowing up the OP's picture, it sure looks like there is a spring there for the parking brake lever. In fact, those calipers look just like the ones on my 96, which most assuredly did have the parking brake built into the caliper.

I don't see any actuating cable for it though,

These are the Dr Diff 11.7 brakes with the 1994-2004 Mustang Cobra calipers.

Those do have the built in parking brake that needs to be used to maintain proper rear brake adjustment and proper brake system function.

I have heard that. I have a 5 speed manual so I do use the parking brake every time I park the car.

To clarify, Mustang calipers have the parking brake. Explorer do not, crown vic do not, F150 do not.