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Discussion Starter #1
Took my 40 for the first test drive today after a year of working on it. The brakes suck! What is your experience with a 4 wheel disc setup that has a 1982 Fj 60 master and power booster that has just been rebuild. All new 3/16" dia. brake lines, mini truck front knuckles and disc brakes, new rear adjustable proportioning valve, new 1979-85 rear cadillac eldorado e-brake calipers with 1/2 ton chevy rotors. I have bled the system many times, both ways. The "old pump till the bubbles disappear and then hold way" and I have pulled a vacuum on the calipers with a mini vac and a collection jar. I have a pretty good pedal, but I don't seem to be able to apply enough pressure to lock the brakes up, even at slow speeds.. 15mph going down about a 15 degree grade. I am running 35 x 12.5 tires. So, what's the consenus?Master to small? Anyone else run this system with better success than I'm having?
 

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w/ my 4 wheel drums and 33's, i can lock them up whenever...well anything over 10 mph probably...mine are very tight and well adjusted..no booster, just a stock '69 m/c..discs are on the way though
 

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I run the 77 master and booster, 38's and 4 wheel disc brakes without a proportioning valve and mine stops OK, but I doubt the tires would lock on pavement.

Does it feel safe? Will they stop good, but not lock up?

Try them out on a loose surface with the prop. valve off and see if you are getting good brakes to the rear.

You may need some help from the rear on your stopping and have cut it out with the prop. valve.
 

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With the monte carlo calipers in the rear of my 40 I can lock up a set of 36" swampers withouth much trouble. I am running the stock 78 brake master cylinder and booster. without the rear proportioning valve I locked up the rear end wayyyyyy to easily <IMG SRC="smilies/eek.gif" border="0"> After installing the proportioning valve and a 2lb residual valve it stops fairly well (I can lock up the brakes on the road).
Does it help if you pump the brakes? Sometimes ou can get all of the air out of a system but without a residual valve in the rear the pads have to travel a larger amount and braking will be poor.
I assume that you took off the old residual valve? If not it is possible that the brakes were "locked" on a bit too much and they glazed already.
also if you didnot bench bleed the system peoperly it would give these symptoms.

Pump the brakes and tell us what you think....
 

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Dave67...I had the same problem and after 3 master cylinders, I went to pick-a-part and grabbed a master and booster off an 80's Cadillac, the booster is about 9" in dia and about 8" long, the master is the one that is about 6" long and 3" wide with the metal cover on the top and a snap wire to hold it on. I can lock them up anytime and no proportioning valve. e-mail [email protected] with any questions.
 

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Some guy out here saved me alot of time and concerns after BTB steered me that way, he told me a tacoma was the answer and believe me it'll gettem glowing!
 

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Originally posted by Jason M:
<STRONG>With the monte carlo calipers in the rear of my 40 I can lock up a set of 36" swampers withouth much trouble. I am running the stock 78 brake master cylinder and booster. without the rear proportioning valve I locked up the rear end wayyyyyy to easily <IMG SRC="smilies/eek.gif" border="0"> After installing the proportioning valve and a 2lb residual valve it stops fairly well (I can lock up the brakes on the road).
Does it help if you pump the brakes? Sometimes ou can get all of the air out of a system but without a residual valve in the rear the pads have to travel a larger amount and braking will be poor.
I assume that you took off the old residual valve? If not it is possible that the brakes were "locked" on a bit too much and they glazed already.
also if you didnot bench bleed the system peoperly it would give these symptoms.

Pump the brakes and tell us what you think....</STRONG>
How do your brakes wear with the residual valve? They don't constantly rub the rotor? Residual valves(as I was told)are only to be used when the master is below the brake pistons or calipers to keep the flow of fluid from backing into and overflowing the master.

I have mini disc's on the front and Downey with Monte Carlo calipers on the back. I run a 78 master with a proportioning valve for the rear. I could lock up my 35's on pavement only after I adjusted the prop valve to lock up the rears just before the fronts. The pedal is not rock hard but is not spongy either. You just have to keep adjusting until it feels right.
 

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Discussion Starter #8
Ok, here's what I tried tonight. First I went over every brake line connection and double checked to be sure they were all tight. Then I pulled the master off the power booster, without disconnecting the brake lines going to it, and measured the distance from the power booster rod tip to the master cylinder piston cup where the rod pushes. The distance between the two when the brake is not being pushed is less than .050 thousands of an inch. So I reassymbeled the master. Next I took the Eldorado calipers off the rear disks leaving them still connected to the brake lines and put a block between the brake pads to keep them from popping the pistons out. I tilted the calipers so that the bleders where at the absoloute highest point then bled the longest line caliper first and the next longest second. Got maybe a bit more air out of them when I did this. Next took some solvent, MEK, and wiped the rotors and pads clean to be sure their wasn't any oil residue. When I tried it out on the same hill I had just about the same results, can't lock the wheels on dry pavement but could, just barely on dirt. On dirt when I stomp on the brakes and watch the front and rear tires they both start to lock at the same time so I think I have the proportioning valve adjusted pretty close.If I pump the brake pedal before trying to lock them It dosen't make any difference in the way the brakes peform . Soooooo am I hosed here with this setup? Coyote are you saying the Tacoma Power/master setup is superior to the Landcruisers can you lock the wheels say at 60 mph on pavement if you wanted too, not to say anyone would want to do this but it would be nice to know it's possible. Does BTB use the Tacoma power/master? Jason did you put the residual valve in front or behind the proportioning valve? It sounds like you feel your brakes work but maybe not as well as you hoped, is this right? Mr Gadget your soloution sounds like it would solve the problem, except for the amount of space it takes up 9" dia. is to big for the space I have. Are you running an Auto tranny? Right now with the 8" dia. booster I have I'm right up against the clutch master. I don't think it would even be possible to slide a piece of paper between them. There must be a way around this problem. Any more suggestions? Their must be some factory 4 wheel disc brake trucks, anybody know what models. I'm really starting to feel that the power booster isn't up to the task.
 

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Dave67.....yes, I'm running a TH400 tranny, tonight I'll get the exact dimensions of the master and booster, it might be 8" in dia, and also the clearance from where the clutch master was, if any. I know exactly what you're going through, I was so frustrated, I called a friend to help dope this out and came to the conclusion that the Toyota master was not up to the task of actuating 4 calipers.
 

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I have a 70 cruiser that had the 4 wheel drums and single master(whoo hooo), scary! I swaped in man-a-frees front disc conversion and am about to swap in JT Outfitters rear disc conversion. They include a FJ80 master that has a auto adjusting porportioning valve built into it. This will bolt on to your stock booster and was designed for 4wheel disc. I hear that it will stop on a dime with this master. Call your local auto parts, they have the FJ80 master for about $80. Hope this helps. <IMG SRC="smilies/biggrin.gif" border="0">
 

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Discussion Starter #11
Status as of today. I called Allpro and another shop. Allpro's FJ80 master is 1" bore but I'm not conviced that just bolting this onto the FJ60 master will solve the problem. Allpro uses the mini truck booster and claimed that it would lock up 37" tires. The other shop uses 76-80 FJ-40 boosters and claim they work. I'm not convinced yet. So I'm checking out late model factory 4wheel disc master/power booster setups that chevy,ford and honda MDX use. One thing for sure is you need a dual diaphram booster of at least 8" dia. to generate the boost you need for 4wheel discs.
 

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Dave67...I measured the master and booster, the booster is 8 3/4 dia, same as the Toyota one I took out so it should fit, the 3 things to be done is the 4 holes thru the firewall, they don't match, add washers for spacing fwd, 2) the push rod, I welded a piece of the Toyota on to the GM one for the right length, and 3) the aft brake line, I reamed out the large GM line 3" from the master and slipped the Toyota line into it and brazed it together, been fine for a couple years. I'll e-mail you a pic of the unit.

[ 08-15-2001: Message edited by: mrgadget ]
 

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Discussion Starter #13
Mr Gadget, I like your solution. I'm going to check out the junkyards this weekend for a 1985 -90 Cad master/booster. Thanks for the info. Makes sense that if you use Cad calipers for the rear may as well use Cad for the rest. Do you know how the weight of the Cad compares to that of a cruiser?
 

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What year fj80 master is $80
i called today and they told me $200?
and will it bolt up to the stock fj60 booster ?

Thanks TIM
 
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