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Discussion Starter · #1 ·
Ok so i got my calipers in for the 8.8 rear end that i am building up to fit under my rig. These are some massive 2 piston guys. Last time i checked, The stock fronts in my 89 are single piston calipers. I figure that i will drive around and if my rears seem a bit grabby try to adjust the proportioning valve. I have read about guys using the proportioning valve from a ZJ. Is that a bolt on situation, and is it just a un bolt brake line rebolt, and bleed brakes? Or is it possible to adjust the stock valve?
 

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you shouldnt have to monkey with your stock one. I didnt and i stop better on 33's then anything else we own
 

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I have a ZJ prop valve on my YJ. It was a straight bolt on to my 93 YJ. All I did was cut off the ZJ's mounting bracket (since the YJ doesnt use one) and then switch over one fitting. Its the one that points at the firewall, it goes to one of the front brakes. On the Zj valve its just a plug, remove the plug and replace it with the fitting off the YJ's old valve and its now a bolt on deal.

What calipers are you useing? I have never seen dual piston calipers for the 8.8
 

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I didn't touch the prop valve on mine. it stopped OK for a while, I just finished the E350 1 ton van master cylinder swap and man what a diffewrence!! I can easily lock up my 35s with no trouble. the swap cost me a total of 45 bucks for the master cylinder and the adapter i needed.
 

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leave the prop valve alone. some people remove the little o ring in there to add more pressure to the back brakes. this is not recommended. you'll lock up in the back before the front. this is bad.

if you really want to make your rig stop, get yourself a vanco hydroboost. you'll throw yourself through the windshield with it :)
i just finished my installation of the hydroboost, and am very pleased with it.
 

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Like Nailer said. however, those things ain't cheap. the E350 MC swap took me all of an hour and cost me a whopping 45 bucks worth of parts. Auto Zone even took my old YJ MC in as the core for the Ford Master Cylinder. All I had to really do to get it in was hog out twoi holes and grind down one of the tabs a little and it bolted right up to the stock brake booster. Made a HUGE difference!! i can easily lock up my 35s by barely tapping the pedal.
 

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92 Green YJ said:
Like Nailer said. however, those things ain't cheap. the E350 MC swap took me all of an hour and cost me a whopping 45 bucks worth of parts. Auto Zone even took my old YJ MC in as the core for the Ford Master Cylinder. All I had to really do to get it in was hog out twoi holes and grind down one of the tabs a little and it bolted right up to the stock brake booster. Made a HUGE difference!! i can easily lock up my 35s by barely tapping the pedal.
what size is the bore on that E350 master?
i am a bit curious about this whole braking thing. i have recently gone through brake 101 with all of the custom braking options i/we have gone through on my jeep.

starting with the corvette master designed for power brakes with a 1" bore.. then to a manual brake corvette master with a 1" bore. the difference the 1/8" smaller bore made in braking sensativity was amazing. the smaller one is so much better.

combine that with the hydroboost which is putting 3000#psi to the caliper.
i started with some cobra calipers, which look great, fit into a 15" wheel, have 2 pistons, and are light weight... but wont stop the damn jeep.

moving then to the wj calipers... these things will clamp down like there is no tomorrow!
i am very pleasd with the wj calipers, and vanco hydroboost combo. there are also explorer discs in the back.

with the wj brakes in front and the stock proportioning valve, the bias is fantastic.
 

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92 Green YJ said:
Like Nailer said. however, those things ain't cheap. the E350 MC swap took me all of an hour and cost me a whopping 45 bucks worth of parts. Auto Zone even took my old YJ MC in as the core for the Ford Master Cylinder. All I had to really do to get it in was hog out twoi holes and grind down one of the tabs a little and it bolted right up to the stock brake booster. Made a HUGE difference!! i can easily lock up my 35s by barely tapping the pedal.
what all is needed for this swap? what year E350 does the mastercylinder come out of?
 

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Uncle Paul has spoken...
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Discussion Starter · #11 ·
ok, i just found out that the calipers that the yard sent me were twin piston fronts...they are sending me the correct single piston rears tomorrow. i was worried cause these are some massive calipers that the explorer use in the front
 

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be sure you read the whole story before you rush out and buy your new 350 master. the bore size is a problem with this thing.
:read: "the bore on this ***** is twice the sise of the yj". this is not a good thing.
92 Green YJ, what brakes are you running in your jeep?

with what i have learned with my quick braking lesson is the simple fact that a smaller bore on the master will increase sensativity, and a larger one will decrease it.
the amount of throw will determine the volume of fluid.

now the bore size on the calipers is another story. a larger bore down there is a good thing. hence the problem with the cobra calipers and their small bore would not stop my jeep, and the quite larger bores on the wj calipers will put you through the windshield.

with the hydroboost, i was/am getting 3000 pounds of pressure at the calipers. the bores do matter.
something more to ponder before you rush out and buy stuff you'll end up putting on ebay ;)
 

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NAILER341 said:
be sure you read the whole story before you rush out and buy your new 350 master. the bore size is a problem with this thing.
:read: "the bore on this ***** is twice the sise of the yj". this is not a good thing.
92 Green YJ, what brakes are you running in your jeep?

with what i have learned with my quick braking lesson is the simple fact that a smaller bore on the master will increase sensativity, and a larger one will decrease it.
the amount of throw will determine the volume of fluid.

now the bore size on the calipers is another story. a larger bore down there is a good thing. hence the problem with the cobra calipers and their small bore would not stop my jeep, and the quite larger bores on the wj calipers will put you through the windshield.

with the hydroboost, i was/am getting 3000 pounds of pressure at the calipers. the bores do matter.
something more to ponder before you rush out and buy stuff you'll end up putting on ebay ;)
but he's living proof that it does work, and after doing the mod himself, and then reporting that he can put you through the windshield on a set of 35's, wouln't that mean it's a good thing???
 

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here is a quote.
The problem isn't "overkilling on pressure".

It's a question of fluid dynamics. Lets simplify it and use one single brake caliper as an example:

If the master cylinder is half the displacement of the caliper, then your foot would travel twice as far as the brake caliper moved (2:1 ratio)... but the caliper would be squeezed with twice the force the brake pedal+power assist were applying to the M/c. You have a pedal with a fair amount of travel, but lots of clamping pressure too.

However, if you swap in a master cylinder with double the displacment, the master and the caliper are now equal sizes. So the caliper moves in a 1:1 ratio to the master, and no longer clamps the rotor twice as hard as the master is pushing. You now have a rock hard pedal (if the system is bled) but you have lost much of your clamping pressure: You've given up your mechanical advantage.

Make sense?
now i am by no means trying to talk you out of trying this.. in fact, i encourage you to try it, and post back your personal findings. hell, it is a cheap mod at less than 50 bucks.
all i am saying is that with the time and money i have spent in the past couple of months trying to make a brake system that works.... i dont believe that switching from a smaller bore master to a larger bore is going to give you better brakes.

thanks blaine for the schooling on hydraulics. :wave:

read through the tread posted, and see the mamy that did this mod, and were not happy with the illusion of better brakes with a stiffer pedal.

with a gauge and hydroboost i/we tested pressure with a 1 1/8" bore master, and pushing as hard as i could with my leg, and hydroboost, i could get about 2400#, which is a whole hell of a lot of pressure considering your stock "power brakes" are achieving around 1000 psi.

now with the 1" bore master, and the same hydroboost with all the same characteristics, pushing on the brakes i was able to bury the needle at 3000 psi to the pin, and had some leg left. now what has changed is the sensativity of the brakes... not so much the pressure.

if my leg was stronger, i would have likely been able to achieve the same pressure with the larger master... but with the smaller... it is easier to push,.

does that make sense?

hell.... try it, and post up your results.:thumbsup:
 

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I'm running the stock discs up front and the stock rear ford 8.8 disc brakes (99 explorer) out back. I was planning to upgrade the calipers initially, but I honestly don't feel it is necessary now with the new master cylinder. Bear in mind I've only had the new MC in for about two weeks. However, in that time I have driven highway, hills, trails, and pulled a 1,000 lb trailer up and down a steep mountain pass. this swap works and works well in my humble opinion. I am very happy with it. I did not topuch the prop valve, just left it alone. all i did was remove the old MC and replace it with the new one and bleed the system. hell the only reason i decided to do the swap was because i was installing a line lock and would have had to bleed the whole system anyway, so I said what the heck and did this too.
 

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gotcha 92,

that's the same setup I'm runnning. stock HP 30 disc's up front and my 8.8 discs in the rear.


heck, for $50 I'll try it this weekend and see how well it works.


I could always swap it back i guess.
 

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Hey Nailer, I just did this swap last night, took me @ 1.5hr from start to finish. As in life, book theory and real world doin are some time 2 very different animals. I can tell you it takes way less pedal psi to stop, when you push as hard as you can, please be sure to be wearing your seat belt, it stops incredebly fast. It cost me $21 for the MC, @$6 for the hard line (with adapters) and $10 for brake fluid. Any one can do this mod, but stock size tires are gona probably be overwhelmed with braking power.
 

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very cool.
i'm glad to hear that it is working for you.
the whole hydraulic theory is a strange one. :rtft: :thumbsup:
 

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leave the prop valve alone. some people remove the little o ring in there to add more pressure to the back brakes. this is not recommended. you'll lock up in the back before the front. this is bad.

if you really want to make your rig stop, get yourself a vanco hydroboost. you'll throw yourself through the windshield with it :)
i just finished my installation of the hydroboost, and am very pleased with it.
Hey! I know this is an old post but did you have any leaking issues with your hydro kit from Vanco?
 
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