Big Brakes

[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.


Sent from my iPhone using Tapatalk

[Tchajagos]

What master cylinder are you using? The proportioning valve is inline with the rears right?

[Andy Jones]

What master cylinder are you using? The proportioning valve is inline with the rears right?

It’s a Wilwood combo valve. So no, it’s not. It mounts next to the Master cylinder. And I’m running the stock Master with a gutted residual valve.


Sent from my iPhone using Tapatalk

[Hillbilly Heaven]

The combo valve is just an adjustable rear prop valve with a brake light switch. Yes the front brake line does connect to it but it does not affect front pressure. What you are calling a gutted residual valve is actually a prop valve. You don't need it at all. It can be eliminated. I don't understand why you are using a 2 pound residual valve in the rear. With disc brakes and MC higher than the calipers there is no need for residual valves.

You main problem though is the master cylinder. It is too small especially for the rear. You need to find a 99 or later Master Cylinder. Something that had factory rear disc. I don't know how much more volume the calipers have over stock but you may have to step up to something off a Super Duty to get the volume and piston size you need.

[Tchajagos]

Was going to say about the stock master. It’s too small for rear disks. We use an expedition master when going to rear disks but if you have bigger calipers in the front it might not be enough. Literally not enough fluid is being pushed through the lines because the masters bore is too small.

[Andy Jones]

The combo valve is just an adjustable rear prop valve with a brake light switch. Yes the front brake line does connect to it but it does not affect front pressure. What you are calling a gutted residual valve is actually a prop valve. You don't need it at all. It can be eliminated. I don't understand why you are using a 2 pound residual valve in the rear. With disc brakes and MC higher than the calipers there is no need for residual valves.

You main problem though is the master cylinder. It is too small especially for the rear. You need to find a 99 or later Master Cylinder. Something that had factory rear disc. I don't know how much more volume the calipers have over stock but you may have to step up to something off a Super Duty to get the volume and piston size you need.

Hmmm..
I’ve been told by numerous people on this site, throughout this entire build, that I would need a 2lb residual valve for the front and rear Wilwoods.
And I know of a few people on here that are running the stock master as well.


Sent from my iPhone using Tapatalk

[Andy Jones]

I’m assuming you’re both running Wilwoods ?


Sent from my iPhone using Tapatalk

[cs_drums]

I’m in the same boat Andy. I have Gm metric calipers in rear stock in front. My brakes are fine for driving but lack volume to really get it slowed down on full oh shot brake situation. As mentioned above I believe it’s lack of volume and a larger bore master is needed I just haven’t got around to it.

I running residuals front and rear for no reason either. My buddy told me I should run them and I don’t remember why. They were $10-20 each so it’s not like it breaks the bank


Sent from my iPhone using Tapatalk

[PaulW]

Another thread with my experience
http://www.gofastbroncos.com/forum/view ... 06#p146306

[LvSteve]

I too have the same prob. I run the 96 F350 master cylinder with a 1.25 bore. The oem bronco master is 1.06 bore. I run a rear 2lb Wilwood residual valve, Forward of the oem fuel filter. It seemed to help pedal height.
Plus the Wilwood Combo valve. With ford calipers
Having the brake system power bleed was a great help !
I can stop hard but not lock up

[Andy Jones]

Do you guys have a nice firm pedal ?


Sent from my iPhone using Tapatalk

[LvSteve]

My pedal gets firm get half way down

[Andy Jones]

Mine is firm all the way through.?


Sent from my iPhone using Tapatalk

[Hillbilly Heaven]

Residual valves were created for use on drum brakes. Vehicles had them built into the prop valve if they had drum brakes. If it had front drum it had two residual valves in the prop valves. Broncos had residual valves for the rear in the prop valve. People think when they gut the factory prop valve for using rear disc they need to add a residual valve. This is 100% Wrong.

Reason a residual valve was used with factory rear drums was to keep the brake shoes close to the drum. If there was no residual valve the springs inside the drum would collapse the shoes completely. This would cause little to no brake as all the pedal travel would be consumed in just moving the shoes out. This is why when adjusting shoes after replacing wheel cylinders you must pump and bleed the brakes first then adjust the shoes. This would then center the wheel cylinder and keep constant pressure on the wheel cylinder.

There is no need to run a residual valve with calipers if they are floating calipers. The floating design allows the pads to always stay in very close contact with the disc. The floating part allows the whole caliper to move to take up for pad and disc wear also for any run out in the disc. If you are running welded brackets to the axle and the caliper bolted directly to the bracket, this is a fixed caliper. There is no movement for the caliper to account for wear.

When do you need a residual valve?
When running drum brakes
When the master cylinder is mounted lower than the calipers or wheel cylinder
When you run fixed calipers so that the pad is kept close to the disc. This does cause excess wear in pad and disc. If you don't run a residual valve you will get very little braking effect as the pads and disc wear.

When do you NOT run a residual valve?
When using floating calipers. A residual valve will cause excessive wear to pad and disc, and additional heat. The floating mechanism will keep the pad close to the disc for instant braking action.


Next post will be about selecting proper master cylinder. Need more coffee first.

[Stan the Man]

Wow, this is very informative.

[toddz69]

Residual valves were created for use on drum brakes. Vehicles had them built into the prop valve if they had drum brakes. If it had front drum it had two residual valves in the prop valves. Broncos had residual valves for the rear in the prop valve.

Or they have them in the master cylinders. On the late model Broncos, aren't they in the big aluminum hex fitting that attaches to the master cylinder?

Todd Z.

[toddz69]

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.


Sent from my iPhone using Tapatalk

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.

[toddz69]

Reason a residual valve was used with factory rear drums was to keep the brake shoes close to the drum. If there was no residual valve the springs inside the drum would collapse the shoes completely. This would cause little to no brake as all the pedal travel would be consumed in just moving the shoes out. This is why when adjusting shoes after replacing wheel cylinders you must pump and bleed the brakes first then adjust the shoes. This would then center the wheel cylinder and keep constant pressure on the wheel cylinder.

I used to think this was the case but a few years ago, I learned the real reason for the residual pressure valve. They're there to maintain a small amount of pressure on the cup seals inside the wheel cylinders on drum brake setups. If you look at an Early Bronco, for example (since I'm most familiar with them), the 7/8" wheel cylinders have an effective piston area of .6 sq inches, so 10 psi only equates to about 6 pounds of force. This isn't enough to effect the drum brake actuation, but is enough to maintain enough pressure on the cup seals such that they remain "inflated" and in contact with the bore upon brake release, when the retraction spring collapses the wheel cylinders. Without this, the seals can crease and/or fold and leak out brake fluid and/or allow air into the system.

Todd Z.

[Tchajagos]

Residual valves were created for use on drum brakes. Vehicles had them built into the prop valve if they had drum brakes. If it had front drum it had two residual valves in the prop valves. Broncos had residual valves for the rear in the prop valve.

Or they have them in the master cylinders. On the late model Broncos, aren't they in the big aluminum hex fitting that attaches to the master cylinder?

Todd Z.

Yes, there is a valve in there.

[Hillbilly Heaven]

Todd,
Yes you are correct on that point but it was mainly to keep the shoes close to the drum. Without the residual valve the springs will collapse the shoes completely. The pressure setting needs just enough to back the shoes up slightly. 2 PSI usually is not enough to keep the shoes pushed out but will keep the seals expanded. 10 PSI will overcome the initial spring pressure.