Why Bronco's don't wanna stop

[mustangtoby]

I've got the same problem with mine. It will panic stop if you REALLY stomp the whoa pedal, but it really has me considering hydroboost. Dammit, I deserve it!

 

[needabronco]

I recently did the front disk conversion, and have all new rear brakes, adjustable prop. valve and all new lines. I've bled my system several times(put 2.5 quarts through it). And I can't lock mine up! It stops really well, much better than before, but a bigger master cylinder and hydroboost are on my horizons... I say go for it.

 

[HoosierDaddy]

That's right.
The smaller the primary piston in a hydraulic system, the more pressure you can apply. ----Blubuckaroo

Ok , I understand the principle there ...
but I had the understanding that the large piston bores in a caliper require more fluid to move , thus the pedal (and MC piston) has to travel a long ways to move the required amount of fluid.
Not argueing , just trying to learn , as some info: on the net isn't quite "fact".

My guess would be that the caliper piston doesn't have to move very far , requiring very little fluid ? (building pressure instead).

 

[HoosierDaddy]

Answered my own question :

http://www.mrwbronco.com/project/honey/brakes.html
From above link :
Allow me to clear up a common misconception about master cylinders. A larger bore provides more volume but less pressure. A smaller bore provides less volume but more pressure. So you should never increase master cylinder bore diameter unless you're also installing larger brake calipers to accept it. If you do, your brakes will only feel better because the added volume shortened your pedal stroke and made it more firm. In reality however, the same calipers are receiving less pressure which just made your brakes worse.

 

[FASTERDAMITT]

I just changed my standard pads out for the EBC Yellow pads. They are supposed by be higher friction at a low temperature. There was a noticable improvement, however its still not good enough. Here is what I have tried so far: Rear disks= no improvement; Dual diaphram booster= some improvement; Vacuum resevoir= some improvement; Wilwood 4 piston front calipers= some improvement; 1" bore MC instead of 1.125"=most improvement yet; EBC Yellow pads= minor improvement. I think I will try H-boost next and quit messing with it. Hope some of this is helpful.

Good info. What master Cylinder did you use?

 

[45acp]

Manual brakes on my old '75, Chevy front disc swap, CJ rotors/Monte Carlo calipers out back with (i think) 78 Vette MC. You could lock 35's up with your big toe.

Im thinking you have a mis-matched MC issue

 

[73AnneBoleyn]

i think my problem is the 1.25" bore MC with my chevy discs up front. firm as hell, but i don't think it's doing much good. also, i'm gonna grind my knuckles a hair further...i think they're getting hung up.

 

[GRN_MEANIE]

Vacuum resevoir= some improvement; Wilwood 4 piston front calipers= some improvement

Vacuum Resivoir???? Is that what the lill' sphere under the hood of my S-10 is it's basically a ball w/ a vacuum line going to it bolted to the underside of my hood.

4 Piston calipers? Cool, custom I assume?

Can say an F-150 D44 be converted to F-250 Brakes?

 

[FASTERDAMITT]

After researching the build log for my Bronco, it looks like the master cylinder may be original. I asume the original m/c is not a good setup for 4wheel discs. Does the original m/c have the lines exit on the drivers side or passenger? I also have a proportioning valve.

 

[Pa PITT]

Man my Bronco has always had such good brakes I like to never added my disk set up ...I had it for 2 years before I was ready to put it on ....only then because one of my front wheel cyl went out ...So I change it at this time ...I have chevy backing plates and calipers and $7.00 disk pads ..80 ford hubs and rotors ...Chevy spindles Chevy rubber hoses ..the org. H block ...stock rear drums ...I bought a stock 72 MC ....If you don't have you hands on the dash,I could plant your face on the windshield ...I have no power yet ..I have about 5 hydroboost I've gathered up but why at this point ....
...But since I'm about to start my 4BT swap I may need it when the extra weight is added ..
...Now I will say my pedal is not soft I do have to push but it will stop...

 

[NYLES]

I can ASTROBOOST YA through the windshield if ya'd like!....or bounce ya head on the cage.

150 front disks, chevy disks rear s10 calipers vette M/C......a modernized break system that works well....and we deserve it!

 

[t.lay]

If you're running out of pedal travel, but an extra pump gets more stopping power I think it's an m/c bore size issue (getting enough fluid/pressure to the piston). If you have pedal left, but not enough clamping force, that may be more of a vacuum/power assist issue.

 

[FASTERDAMITT]

I have travel left. It stops good with a firm pedal but you can stand on the pedal and it does not stop any better. Almost like it is brake pad fade. I just checked my claiper to knuckle clearance again. No issue there. I think I may need a cheap pad or different M/C.

 

[FASTERDAMITT]

Looking at the master cylinder, it's a 1 1/16" bore. The reservoirs are not equal capacity. The rear is larger than the front reservoir. Is this a disc drum M/C ?

 

[73AnneBoleyn]

the rear reservoir is bigger than the front, no matter if it is drum/drum or disc/drum.

 

[Mikey]

The drum portion of any MC will have a 10 psi residual valve built into them causing that pad to drag when installed onto a disk system. You will be able to tell by the extreme heat and brake fade.

A stock combo valve (commonly and mistakenly called a proportioning valve) for a disk/drum system is used to balance the disk/drum bias at low and high pressure demand. If you are using this on a 4 disk system, it is incorrect. I'm pretty sure you just need an H valve with an adjustible proportioning valve.

I've also noticed that with soft springs that we all like in the rear, the axle will wrap up giving a mechanical delay for the rears to transmit braking. This gives kind of a weird feel that the brakes aren't quite grabbing right. Some sort of axle wrap bar(s) will fix that nicely!

Make sure your MC is right and the rod is adjusted correctly. Do a search here for all kinds of info.......

Good luck!

 

[NYLES]

Mikey Im using the original H block from a drum/drum on my disk/disk works great!

 

[FASTERDAMITT]

Sounds good.

 

[FASTERDAMITT]

Solved!

Solved! I installed new Duralast semi-metalic pads and I can lock up all four! Wish I would have figured this out long ago, how simple. i don't know what I took off but they looked to have alot more metal in the pad.

 

[Pa PITT]

So how expensive are the ones you put on ..are they auto zone cheap pads...
I have thought in the past the cheaper ones stop better just wear out faster which is not much of a problem for my Bronco ..