Big Brakes

[Hillbilly Heaven]

I have never examined the fitting you are talking about. Should only be a small spring and a steel ball. Once the pressure gets too low to overcome the spring the ball will shut off the port.

[Andy Jones]

How many of you guys have made the switch to big Brakes ?
I’m running Wilwood 4 pistons on the front and rear, with a 2lb residual valve. And a proportioning valve. The Brakes seem to be holding great pressure and they’re very responsive.. The only problem is, they’re not locking up the Bronco when in panic mode ! Just wondering what your guys thoughts are on this.


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Which Wilwood calipers are you running on the front and are you running stock rotors or something larger?

Many of the so-called 'big brakes" I see actually use calipers with a smaller overall effective piston area than the stock calipers. Even with slightly larger rotors, the resultant brake torque is less than the stock setup assuming no changes are made to the master cylinder diameter.

Todd Z.

I’m running the Wilwood superlite 4 pistons front and rear. 1.25 pistons with a 13” rotor in the front. The rear is the same, it’s a full floater housing with big brakes.


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[toddz69]

Those brakes are great for the rear but, in my opinion, far too small for the front. You only have 2.46" of piston area, which is less than half the stock caliper's piston area. Granted, you have stiffer calipers and slightly larger rotors, but you're nowhere near enough brake torque in my opinion. I think you'd find a switch to the version of those calipers with 1.75"/1.88" pistons would make a difference.

Todd Z.

[Andy Jones]

I meant 1.75”
After a little bit of adjustment and another brake bleed. They work amazingly.


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[Hillbilly Heaven]

Hope I have my head screwed on right, so if I make mistakes forgive me and I will correct them.

First off, Todd thanks for commenting on the front caliper piston size. Glad you knew what the stock piston area was. He will for sure need a larger master cylinder.

Now if he goes with a master cylinder with a larger bore what happens to braking effort and pedal feel? When comparing MC bores keep in mind the larger the bore the less brake line pressure you have for the same pedal force. You will notice you will have to apply more force to the pedal. The brakes will be less sensitive. That does not mean they will not lock up, just that you will have to push harder. If you don't like that feeling you can adjust the point where the master cylinder connects to the pedal. Since your pedal is top hung pivot if you raise the point of MC connection you will apply more force to the MC with less pedal pressure, but will take more pedal travel. If you move the connection point you need to move the MC as well. You want as straight a push as possible.

Best comparison I can make is to think of a 600 pound man standing barefoot on a wooden floor. His foot is putting force over a large area but the pound per square inch of pressure on the floor is low. Now put him in spiked high heels. He is putting force on a smaller area of floor, but the pounds per square inch is higher. If he stomped he would make a bigger hole in the floor barefoot than he would with spiked heels, but it would take more force barefoot than with the spiked heels.

Master cylinder, caliper, and pivot point selection is a complicated balancing act. There is some tech documents on Wilwood's website that goes into describing this with diagrams. I suggest to everyone to read those if they are thinking of upgrading their brakes.

My best recommendation I can offer is to call Wilwood techs. Give them the info of what you have brake wise, vehicle weight, tire size, and pedal dimensions. They will be able to make a recommendation on what size MC bore you need. You should be able to find something that is close to this in the 99 and later Ford OEM line.

[Hillbilly Heaven]

Whew if I had just waited a few minutes I could have saved typing all that.

Glad you got it working!! Curious what is your minimum pedal height from the floor when you achieve lock up. Just apply the brakes sitting still using the same force you did to achieve lock up.

Also what adjustments did you make?

[toddz69]

I meant 1.75”
After a little bit of adjustment and another brake bleed. They work amazingly.


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OK good. With that piston diameter and the slightly larger rotor diameter, you're probably closer to the stock bias so I think it should work pretty well.

Todd Z.

[toddz69]

First off, Todd thanks for commenting on the front caliper piston size. Glad you knew what the stock piston area was. He will for sure need a larger master cylinder.

Since his front calipers are still a little undersized compared to the stock calipers, I think he'd probably want to go exactly the opposite - slightly undersize from stock. But it sounds like his stuff is working pretty well and to his satisfaction now so I'd leave well enough alone.

Todd Z.

[Hillbilly Heaven]

Yeah since he did have the size you recommended then yes he should be ok on front. I meant if he went from the size he originally posted and the size you suggested.