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Discussion Starter #1
After I put my 1 ton axles in, I noticed that my brake pedal was pretty low. I have disc brakes in the rear from a 77 K20.

So, I removed the o-ring from the combination valve of my TJ and I read somewhere on this board once that a guy tried adjusting the outer push rod in order to raise the pedal and have better braking. I did that and it actually worked! It took me about 5 tries to get it right because that push rod is pretty sensitive. All I can say now is that my jeep can stop now with 38" much better than it did when I had stock tires.

Anyways, my point is why would people go through the trouble of changing the stock MC to a dodge 3500 MC or even sometimes the booster to get better brakes?
 

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Anyways, my point is why would people go through the trouble of changing the stock MC to a dodge 3500 MC or even sometimes the booster to get better brakes? [/B]

Fawk if I know half of them spend $300 dollars on something that just doesnt work then they spend 2 weeks trying to figure it out & it's something stupid most of the time, they need to keep the stock shit first & tweek on all the brake shit before they go by all new M/C ,booster and so on!! I got a 93 wrangler with 60 & 14 bolt 4 wheels disc & I can lock up my tires with no problem & I'm still running stock booster, M/C & porportioning valve
 

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Congrats, but can you elaborate on adjusting the outer pushrod. Did you use an adjustable pushrod, spacer or what?
 

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Discussion Starter #4 (Edited)
AK TJ said:
Congrats, but can you elaborate on adjusting the outer pushrod. Did you use an adjustable pushrod, spacer or what?
1) remove the 2 nuts that hold the combination valve on the booster studs.

2) remove the 2 nuts that hold the MC on the booster studs (same ones as the combination valve).

3) Pull the MC out away from the booster, you will see that the outer push rod have a miniature bolt at its tip. You can srew this bolt in or out. Adjust out to raise the brake pedal.

4) When you do an adjustment, you have to drive the jeep for a few miles until the vacuum builds up completely otherwise your brakes will start locking up on the street if you have unscrewed the adjusting bolt too much.

HTH
 

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Discussion Starter #5
One more thing, after driving my jeep on the hiway for a few minutes I noticed that my brakes started locking up even though it was fine on the street. Maybe because the vacuum will build up faster in the booster at higher RPMs.

Adjust the screw one turn at a time.
 

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hmmm... i may just have to try that. I was just thinking of going the van hydroboost and no $$$ to do it.
 

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Blue Angel, thanks for the info!!!! I'm printing this thread out and hanging it on the garage wall for my 1 ton conversion!!! This is just the kind of homegrown tech that makes pirate4x4.com the BEST place to get real world tech that's not sponsered by a company just trying to take my money.
Good job

Kevin
 

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Ugh this whole thread screams ignorance. I'm glad that worked for you, but lengthening the push rod should not give you better braking if the push rod was adjusted properly in the first place. Like you said if you scew it out too much the MC will lock up. There is only one right length for the push rod, any shorter or longer, and your MC is not working properly.

The reason people switch master cylinders is really fairly straight forward and simple. When you put on one ton calipers either ford or chevy, the volume of the pistons is considerably larger than that of the stock caliper pistons on a Jeep. This means that it requires more volume of brake fluid to fully actuate the calipers. The stock master cylinder on a Jeep has a fairly modest stroke and bore, which provides adequate line pressure, but bottoms out before providing enough fluid volume to fully actuate the pistons. Your brakes will work, but will not work fully. They will get even worse as the nominal diameter of the rotors wear down and the pads wear out, as the piston now has to move even farther to press the pads against the rotors.

Then there is the fact that the stock MC has a tiny resevoir for the rear brakes, as it was designed for rear drums. Drums use a small amount of fluid to activate the wheel cylinders, and that amount does not change as the shoes wear. If you put on rear discs with rear calipers you now require considerably more fluid to activate the pistons. You run a real risk of draining that resevoir dry as you apply the brakes and then introducing air into the lines.
 

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I think MNBen hit the nail on the head! I swaped in a rear 60 with disks in My YJ and the stock MC/prop. valve just didnt cut it. I tried tweaking all the stock stuff but nothing fixed it properly.
I installed a Corvette MC (which is set up for front AND rear disks, unlike the Ford van MC everyone uses) and an adjustable prop. valve.
Now I can lock up all 4 of My 39.5" TSL's with no problem. Well worth the $30 for the Corvette MC and $50 for an adjustable prop. valve in My opinion :flipoff2:

Matt
 

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Discussion Starter #11
MNBen said:
Ugh this whole thread screams ignorance. I'm glad that worked for you, but lengthening the push rod should not give you better braking if the push rod was adjusted properly in the first place. Like you said if you scew it out too much the MC will lock up. There is only one right length for the push rod, any shorter or longer, and your MC is not working properly.

The reason people switch master cylinders is really fairly straight forward and simple. When you put on one ton calipers either ford or chevy, the volume of the pistons is considerably larger than that of the stock caliper pistons on a Jeep. This means that it requires more volume of brake fluid to fully actuate the calipers. The stock master cylinder on a Jeep has a fairly modest stroke and bore, which provides adequate line pressure, but bottoms out before providing enough fluid volume to fully actuate the pistons. Your brakes will work, but will not work fully. They will get even worse as the nominal diameter of the rotors wear down and the pads wear out, as the piston now has to move even farther to press the pads against the rotors.

Then there is the fact that the stock MC has a tiny resevoir for the rear brakes, as it was designed for rear drums. Drums use a small amount of fluid to activate the wheel cylinders, and that amount does not change as the shoes wear. If you put on rear discs with rear calipers you now require considerably more fluid to activate the pistons. You run a real risk of draining that resevoir dry as you apply the brakes and then introducing air into the lines.

This is all common brake knowledge, how about you buy your new MC and booster for $$$ and I adjust mine for free. Sure it took me a few tries to get it right but hell it cost me nothing... I can basically stop my jeep on a dime, to each his own I guess.
 

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this certainly is interesting. I believe the theory behind the lack of volume in the stock MC to be accurate, but then why is adjusting the push rod apparently working so well? is the increase in pressure just putting a band-aid on the volume issue?
 

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Lengthening the pushrod will not increase the pressure, it lengthens the stroke by removing the freeplay.
reading this thread, it appears that ALL freeplay is removed, which is why the brakes lock up so quickly whne the vacuum starts getting to where it should be in normal driving.
Does it work? According to a couple of people here it does.
Does it really corect the volume problem of the m/c not giving enought fluid to the calipers, I don't think so. What I believe it that this is a band-aid, and not a cure.
 

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All very interesting. Braking is arguably the most important aspect of the Jeep that we need to have working properly, esp. running 1 tons and larger meats.

I installed a Corvette MC (which is set up for front AND rear disks, unlike the Ford van MC everyone uses) and an adjustable prop. valve.
Mattsyj7 - Where did you pick up the Corvette MC?
 

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MountaineerMac said:
All very interesting. Braking is arguably the most important aspect of the Jeep that we need to have working properly, esp. running 1 tons and larger meats.



Mattsyj7 - Where did you pick up the Corvette MC?
From me, I was his parts whore for it. The mc you want is a 69 vette with a 350, and power brakes. They used to be around $20, but they have gone up to around $30 . At $30 I'll buy the correct mc for my application rather than @#$% around with an undersized mc not even close to being correct for the application.
 

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MNBen said:


From me, I was his parts whore for it. The mc you want is a 69 vette with a 350, and power brakes. They used to be around $20, but they have gone up to around $30 . At $30 I'll buy the correct mc for my application rather than @#$% around with an undersized mc not even close to being correct for the application.
With this master cylinder, do you need the adjustable prop valve, or will the stocker work with the o-ring removed?
 

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it sounds like this Vett MC bolts up to the stock booster? If so I might make the swap before I bolt the D60's up to have one less thing to do when they finally make it under. Sounds much more straight forward than some of the other conversions I've heard about.
 

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i think the vette m/c works on the old style cj booster, for a tj you will need a Dodge 2500/3500
 

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The vette mc works with the YJ booster which is what Matt and I have. You need to grind the area where the mc seats to the booster a tiny bit, and wobble out the mounting holes. It is basically the same as the E350 modifications. The mc works just fine with the stock proportioning valve, but it is designed for dual disc applications, so you would want to find a combination valve for dual discs, or at least remove the o ring. The combination valve from a rubicon should work.
 
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