A difficult brake conversion question

[Hedgehog]

Background - '75 CJ5 with stock drum brakes ......

Modification - Installing a 1977 front axle with disk brakes. These brakes are two year only items with the thick rotors. The rotors are in good shape. They are new but have surface rust from sitting around. The calipers and pads are new also. The PO was in the process of rebuilding his jeep but stopped for some reason.

Problematic next step - I know that a new Master Cylinder and Proportioning Valve will be needed. My Jeep guy is nervous about recommending the parts that I will need so I'm coming to you guys for advice. If you have done this popular upgrade and are happy with the results, what parts did you use?

 

[tarry99]

Background - '75 CJ5 with stock drum brakes ......

Modification - Installing a 1977 front axle with disk brakes. These brakes are two year only items with the thick rotors. The rotors are in good shape. They are new but have surface rust from sitting around. The calipers and pads are new also. The PO was in the process of rebuilding his jeep but stopped for some reason.

Problematic next step - I know that a new Master Cylinder and Proportioning Valve will be needed. My Jeep guy is nervous about recommending the parts that I will need so I'm coming to you guys for advice. If you have done this popular upgrade and are happy with the results, what parts did you use?

Should be the 1.125" thick rotors (make sure you measure them) with the single large Piston caliper..... normally referred to as the "Big Brake" option for 77-78 CJ5 's. Great system that should also have 6 bolt hubs and also Warn Premium hubs factory installed. At the parts house the question they will ask is if it is a two bolt or 6 bolt mount? The 1.125" rotors are referred to as the 6 bolt.
Rust on the rotors is no problem as long as there not all pitted.

You should now have swing pedals , is your drum system power boosted? If not I would do an 8 inch dual diaphragm vacuum boosted Power system and yes you do need a proportioning valve although some Masters have that option built in.............If the system is powered it's an easy bolt up........if non power the ratio at the brake pedal has to be changed as non power is about 7:1 whereby power is about 5:1.......all the parts are off the shelf.........although you may have to break into your brake lines up front to add those parts..........a picture of your firewall and brake pedal set from inside would be great. You will need at least a Master Cylinder as the Disc's take more volume and a different sized bore is used for that purpose.

Easy to do have done many!

 

[Hedgehog]

I generally don't like quoted responses, but you covered a lot of ground and I want to understand.

Should be the 1.125" thick rotors (make sure you measure them) with the single large Piston caliper..... normally referred to as the "Big Brake" option for 77-78 CJ-5's. Great system that should also have 6 bolt hubs and also Warn Premium hubs factory installed.

This confuses me a bit. I'm sure the hubs are the standard 5x5.5 lug pattern. Where does the 2 bolt vs. 6 bolt pattern come into play?

At the parts house the question they will ask is if it is a two bolt or 6 bolt mount? The 1.125" rotors are referred to as the 6 bolt.
Rust on the rotors is no problem as long as there not all pitted.

You should now have swing pedals, Yes, I have swing pedals that are standard on my '75 CJ5. It has standard non-boosted brakes and to be honest I'd like to keep them that way. I'm both a bit of a luddite and a KISS advocate. It is also nice to keep having brakes when a steep hill makes for an engine stall. is your drum system power boosted? If not I would do an 8 inch dual diaphragm vacuum boosted Power system and yes you do need a proportioning valve although some Masters have that option built in.............If the system is powered it's an easy bolt up........if non power the ratio at the brake pedal has to be changed as non power is about 7:1 whereby power is about 5:1 What? Where does the 5:1 or the 7:1 ratio come into play? Are we talking about something internal in the MC or the Proportioning valve or is this a mechanical ration like pivot the point on the pedal arm? .......all the parts are off the shelf.........although you may have to break into your brake lines up front to add those parts .... Would this be to have the correct fittings on the brake lines?......a picture of your firewall and brake pedal set from inside would be great. ....Easily said, not so easy to do, the pedal set looks about like any other to me. .... You will need at least a Master Cylinder as the Disc's take more volume and a different sized bore is used for that purpose.

Easy to do have done many! Seems easy enough, but I want to get the parts correct the first time. Rob at Willys Works has had some problems with these conversions. Sometimes there wasn't enough brake to skid the tires, other times there was FAR too much brake. He suggested that I come here to see if there is something he was missing. Are there any parts houses you prefer over the others as there are many that offer brake parts.

 

[tarry99]

I generally don't like quoted responses, but you covered a lot of ground and I want to understand.

Should be the 1.125" thick rotors (make sure you measure them) with the single large Piston caliper..... normally referred to as the "Big Brake" option for 77-78 CJ5 's. Great system that should also have 6 bolt hubs and also Warn Premium hubs factory installed.

This confuses me a bit. I'm sure the hubs are the standard 5x5.5 lug pattern. Where does the 2 bolt vs. 6 bolt pattern come into play?
Reply:
The 2 bolt mount is the STD. caliper mount that was used on the smaller Disc option of the day..........The Heavy Duty "Big Brake" option used a Caliper mount bracket that circled the entire hub and was attached via the same 6 bolts that held the hub on. See the photo below

At the parts house the question they will ask is if it is a two bolt or 6 bolt mount? The 1.125" rotors are referred to as the 6 bolt.
Rust on the rotors is no problem as long as there not all pitted.

You should now have swing pedals, Yes, I have swing pedals that are standard on my '75 CJ5.

It has standard non-boosted brakes and to be honest I'd like to keep them that way. I'm both a bit of a luddite and a KISS advocate. It is also nice to keep having brakes when a steep hill makes for an engine stall.
Reply:
You can use a manual system , but then you would have to be very creative on the math & piston size of the Master cylinder and mechanical pedal advantage in order to generate the type of pressure usually needed which is around 1200 + psi for the calipers to do there job..........."Dual chambered Vacuum Booster" is why I specked it that way.........gives you more than two full complete cycles of the brake pedal to stop..........even when the vacuum is totally gone.......they turn back into manual brakes.......although the pedal ratio would require more foot pressure........Pretty standard safety requirement in all vehicles. One other nice thing about the power system is the better braking that you will have with over sized tires


is your drum system power boosted? If not I would do an 8 inch dual diaphragm vacuum boosted Power system and yes you do need a proportioning valve although some Masters have that option built in.............If the system is powered it's an easy bolt up........if non power the ratio at the brake pedal has to be changed as non power is about 7:1 whereby power is about 5:1 What? Where does the 5:1 or the 7:1 ratio come into play? Are we talking about something internal in the MC or the Proportioning valve or is this a mechanical ration like pivot the point on the pedal arm? .......all the parts are off the shelf.........although you may have to break into your brake lines up front to add those parts .... Would this be to have the correct fittings on the brake lines?......a picture of your firewall and brake pedal set from inside would be great. ....

Easily said, not so easy to do, the pedal set looks about like any other to me.
Reply:
It is fairly easy to crawl under and measure the ratio......since it's known that it is non-power that ratio would be too great while being used on a Power Vacuum system! It would be very touchy that is why the factory slows it down by taking away some of the mechanical advantage. In some factory pedal sets there was two holes drilled in the arm that the push rod to the master could go in.........some sets just had one , but the other hole is easily drilled. The ratio is derived from the upper fulcrum or pivot point to where the push rod is attached divided by the total length of the pedal from the fulcrum to the foot pad

.... You will need at least a Master Cylinder as the Disc's take more volume and a different sized bore is used for that purpose.

Easy to do have done many!

Seems easy enough, but I want to get the parts correct the first time. Rob at Willys Works has had some problems with these conversions. Sometimes there wasn't enough brake to skid the tires, other times there was FAR too much brake. He suggested that I come here to see if there is something he was missing.
Reply:
This response was just answered above............the reason it was not enough to skid the tires was pressure and ratio related and more than likely the pedal set ratio was never checked...........same holds true when there was FAR to much brake pedal pressure when a Power Booster is added to a mechanical ratio pedal set or too much ratio..............your friend at Willys Works should apply , understand and pay attention to basic Hydraulic principles..........IE: Piston size , stroke, volume and pressure............this is the same principles that all Engineers from all the Auto and Truck Manufactures use when designing a Brake System for a car or truck and given GVW. No Magic here if you to the calculations and apply the principles the Brake system does its job as it is designed to do.

Are there any parts houses you prefer over the others as there are many that offer brake parts.

These are standard off the shelf parts...........Give me a few days and I'll go back and do some research on those part numbers...........you need to confirm what brake system you have......1.125" thick rotors is the start and also look at the caliper bracket.

I'll post a picture of the Standard Caliper for that "Big Brake" system. Also look at that Caliper mounting bracket that is on the Mill.......(these are being modified to rotate to another position) yours would just have 6 holes....that should be what you have if you have the "Big Brake" option..........also the hubs should be 6 bolt Warn's ..........the Standard hubs were only 5 bolt.

This may all sound Confusing but it really is not!






Read more: http://www.jeep-cj.com/forums/f2/difficult-brake-conversion-question-24247/#ixzz3QNGFVagd

 

[GARGOYLEJEEPER]

10 disc lug bolts 1/2" - 20.
may/may not need to machine hubs for disc.
12 disc spindle bolts/knuckles machined.
12 stover nuts.
2 caliper mounts (6 bolt spindle mount).
2 dust shields (6 bolt).
2 hoses.
2 hose bolts w/4 brass washers (if not with calipers).
2 caliper mount kits (key, support, bolt & anti rattle clip)
brake lines or make yours fit.
1 large bottle brake fluid.
1 or 2 tube/s anti squeak. (pad glue)
1 or 2 tube/s disc brake grease. (caliper)
1 can black paint (chassis black)

And as you stated MS (discs) & prop valve (discs)
rod pedal to MS (disc) or make yours fit.

 

[73CJ]

I had the same set up years ago.

I used a master cylinder from a 78 Corvette manual brakes.

Worked great. Used the stock proportioning valve.

 

[Hedgehog]

Okay - thanks for the input

Gargoylejeeper (and others) - Everything on the axle is consistent with the big 6 bolt set-up. So, the information from the calipers on up is what I needed. Is there a difference in pedal rods, I take it we are talking about the rod from the pedal pivot to the MC.

tarry99 - Your information is, well it's most certainly to the point and detailed. Do I have this right? You believe that going with a powered system is the way to go, but if I go with that system I need to change the mechanical ratio on the pedal. Some pedals already have two holes in them .... or does the bracket have the holes? That would logically lead to the conclusion that a system with manual pedal location would already have the correct ratio.

I understand the positives of power brakes, but I also like the simplicity and lets face it the cost savings of standard brakes.

 

[tarry99]

Okay - thanks for the input

Gargoylejeeper (and others) - Everything on the axle is consistent with the big 6 bolt set-up. So, the information from the calipers on up is what I needed. Is there a difference in pedal rods, I take it we are talking about the rod from the pedal pivot to the MC.

tarry99 - Your information is, well it's most certainly to the point and detailed. Do I have this right? You believe that going with a powered system is the way to go, but if I go with that system I need to change the mechanical ratio on the pedal. Some pedals already have two holes in them .... or does the bracket have the holes? That would logically lead to the conclusion that a system with manual pedal location would already have the correct ratio.

I understand the positives of power brakes, but I also like the simplicity and lets face it the cost savings of standard brakes.

Okay - thanks for the input

Gargoylejeeper (and others) - Everything on the axle is consistent with the big 6 bolt set-up. So, the information from the calipers on up is what I needed. Is there a difference in pedal rods, I take it we are talking about the rod from the pedal pivot to the MC.

OK SO YOU HAVE CONFIRMED VIA THE PHOTOS I SUPPLIED THAT THE CALIPER AND THE CALIPER BRACKET IS THE 6 BOLT SETUP IS THAT CORRECT?……….DID YOU MEASURE YOUR BRAKE ROTOR THICKNESS? SHOULD BE ABOUT 1.125” THICK.
THE PUSH ROD COULD BE THE SAME OR DIFFERENT, JUST HAVE TO WAIT & SEE DURING THE INSTALL OR AS YOU READ BELOW THERE MAY BE ANOTHER OPTION

tarry99 - Your information is, well it's most certainly to the point and detailed. Do I have this right? You believe that going with a powered system is the way to go,

YES ON THE POWER BRAKES ESPECIALLY WITH OVERSIZED TIRES, MAKES A WORLD OF DIFFERENCE WHEN STOPPING AND ALSO GOING THROUGH STREAMS OR WATER YOUR NOT AS MUCH CONCERNED WITH THE NEED TO HAVE ALL YOUR BRAKES DRY OUT AS YOU WOULD BE WITH DRUMS ALL THE WAY AROUND

but if I go with that system I need to change the mechanical ratio on the pedal. Some pedals already have two holes in them .... or does the bracket have the holes?

THE PEDAL ARM THAT REACHES FROM THE PIVOT OR FULCRUM POINT TO THE FOOT PAD HAS THE HOLE OR HOLES IN IT...SOME PEDAL SETS DO HAVE TWO HOLES WHILE OTHERS ONLY ONE.... A FACTORY SUPPLIER ANOMALY I WOULD GUESS?……….THERE MAY ALSO BE A HOLE THERE FOR A RETURN SPRING. THE HOLE WHERE YOUR PUSH ROD TO THE MASTER IS NOW LOCATED FOR THE MANUAL SYSTEM SHOULD BE ABOUT 2.5 “ DOWN FROM THE PIVOT"………IF THERE IS ANOTHER HOLE IT WILL BE BELOW THAT BY ABOUT ANOTHER INCH.

That would logically lead to the conclusion that a system with manual pedal location would already have the correct ratio.

I THINK YOUR MISSING THE POINT ON RATIOS………….FOR MANUAL BRAKES IT REQUIRES MORE MECHANICAL ADVANTAGE AT THE PEDAL TO MAKE THE FORCE THE SYSTEM REQUIRES TO STOP. AS I MENTIONED MANUAL NEEDS TO BE AROUND 6-7:1………POWER BRAKES BECAUSE YOU ARE GETTING MOST OF THE PRESSURE THROUGH THE VACUUM BOOSTER THE BRAKE PEDAL RATIO NEEDS TO BE REDUCED………TO AROUND 4:1………THE CLOSER TO THE PIVOT POINT YOUR PUSH ROD IS , THE MORE MECHANICAL ADVANTAGE THERE IS AT THE PEDAL…………VS THE POWER SYSTEM HOLE IF IT WERE THERE WOULD BE BELOW OR FARTHER AWAY FROM THE PIVOT……THIS IS PROBABLY WHY YOUR FRIEND ROB @ WILLYS WORKS WAS HAVING ERRATIC BRAKE ISSUES AND PERFORMANCE IN SOME OF HIS INSTALLS

I understand the positives of power brakes, but I also like the simplicity and lets face it the cost savings of standard brakes.

POWER BRAKES ARE IN ALMOST 100% OF THE VEHICLES BEING BUILT TODAY…….THEY ARE VERY SIMPLE AND AS RELIABLE AS THE SUN COMING UP TOMORROW! YES, THERE IS AN INCREASED COST……….. SAVE YOUR MONEY AND GATHER YOUR PARTS AND DO IT ALL AT ONCE…………….WHY DO IT TWICE? YOU’LL BE GLAD YOU DID ONCE YOU DRIVE YOUR JEEP!

CALL THESE FOLKS AT POWER BRAKE SALES 800-624-8185 IN CALIF.
(PBS Home) THIS IS AN OLD FAMILY OWNED BUSINESS , MORE THAN LIKELY YOU WILL TALK WITH ONE OR THE OTHER OF THE OWNERS TWO DAUGHTERS………..EITHER ONE IS VERY CAPABLE IN TALKING BRAKES , THEY GREW UP IN THE BUSINESS! BELOW IS ONE OF THERE KITS THAT IS ON THERE SITE THAT MAY WORK FOR YOU…………http://www.powerbrakes.com/PDF/the whole shebang chrome RWB 8-1-2013 v2.pdf

IN EITHER CASE TELL THEM WHAT YOUR DOING USING THE DISC’S UP FRONT (CALIPER PART # SHOULD BE RAYBESTOS #4086 & 4085) AND THE 11” DRUMS IN THE REAR……….THEY WILL SPEC OUT THE COMPLETE SYSTEM FOR YOU.
THE LAST TIME I DID A REWORK ON A SYSTEM LIKE YOURS I USED THERE MASTER CYLINDER PART # MC-1321H


HERE IS A PICTURE OF ANOTHER BOOSTER AND MASTER CYLINDER KIT AND IF YOU LOOK CLOSELY THE ADAPTER UP FRONT THAT MAY BE NEEDED FOR SPACING AWAY FROM THE FIREWALL AND FOR HOOD CLEARANCE. IN SOME CASE'S THE OFFSET ADAPTER CAN ALSO CORRECT THE PEDAL RATIO YOU NOW HAVE WHICH WOULD ALLOW YOU TO USE YOUR CURRENT PUSH ROD LOCATION............BUT YOU STILL MUST CHECK IT!.

GOOD LUCK!

 

[Hedgehog]

Tarry99 - Maybe I didn't write my posts very well. No question through measurements and checking visually the Axle is DEFFINATELY the 6 bolt/thick rotor item. Your pictures helped, but I did know what I had.

As far as ratios are concerned, You wrote your information quite well. I understood the first posted information completely. Thank you.

I just needed a few items cleared up, you didn't need to yell at me with Bold Capitol Red letters. Your information was/is very much appreciated, again thank you very much especially the business and phone number.

 

[tarry99]

Tarry99 - Maybe I didn't write my posts very well. No question through measurements and checking visually the Axle is DEFFINATELY the 6 bolt/thick rotor item. Your pictures helped, but I did know what I had.

As far as ratios are concerned, You wrote your information quite well. I understood the first posted information completely. Thank you.

I just needed a few items cleared up, you didn't need to yell at me with Bold Capitol Red letters. Your information was/is very much appreciated, again thank you very much especially the business and phone number.

Not sure what Ya mean about Yelling? The Red just sticks out..........Good Luck on your Project!

 

[Hedgehog]

In the internet world Capital letters = yelling, then add red is really yelling. Usually used when a poster is fed up and pissed. I figured either we simply weren't communicating or you simply didn't know about the yelling thing. I'm glad you aren't actually upset with the way this thread has been going.

Your input really did help.

 

[007]

Hedge there's a site www.the-jeep-guy.com that sells a lot of brake hardware for CJs and some parts as well for those doing conversions. He has the "right" proportioning valve for you as well. He also sells custom brackets for using 1/2 ton Chevy truck calipers (easier to install, replace pads).

Additionally there's a thread on here somewhere about how to make a proportioning valve tool (needed to properly bleed system).


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[Hedgehog]

Thank you, in addition to the technical information sources are the type information I need. Thank you.

 

[Hedgehog]

This is becoming quite the process. Called the "The-Jeep-Guy" and the folks at "The Whole Shebang".

''The-Jeep-Guy" is one enthusiastic Jeeper and he seems to know what he's talking about. Unfortunately the first thing he believes in is to get rid of most of the parts I have and go with a pretty much GM conversion. New rotors, new brackets, new calipers, new pads Errrrrrrrr But my jeep stuff that came with the axle was already new. Unfortunately I can't dismiss what he had to say and all of it was logical. The rotors and calipers are Ford products, these brakes tend to hang and wear prematurely on the inside. Over all the GM parts last longer. He says not to get the rotors or the calipers from him, it's cheaper to get them from O'rielly's or some other chain store.

He has the GM conversion brackets, hoses, master cylinder/booster/bracket ..... and a ton of enthusiasm which I enjoyed, but had little time for (the phone battery was going dead).

We will just have to see how this spins out.

I'm waiting on a call back from the "The Whole Shebang" guy. I'm betting he will not tell me to get rid of my Ford parts, lets see.


Edit: Just heard from the "The Whole Shebang" folks. They had the best idea of all. The booster/master/brackets are all the same units, so I should get the parts and try them, if I don't like the results, then do the GM rotor conversion. Seems logical enough with no real wasted parts.

All-in-all this has been interesting so far, both companies were straight forward and honest, I'd do business with them both and probably will in the future.

 

[GARGOYLEJEEPER]

At least you are having fun and that is what it is all about. Being able to work, fix, modify, learn & play with our grown up toys. :grinjeep:

 

[Hedgehog]

Yeah - For me spending this kind of money is never fun, but the work and the learning is enjoyable. Honestly I've got and have had so many unfinished projects going I'm getting sick of waiting to finish things. It's time to "Git'er Done".

 

[007]

I understand exactly what you're saying Hedge. It's like anything else with these darn things, you always feel like you need to do something extra "while you're there".

I need to replace my front calipers and there's no way I'm putting those Ford ones back on. What a ridiculous design. I'm going to get my brackets from the jeep guy then go pick up on my Chevy hardware at Autozone and stuff my Ford stuff back in the box for the core. They'll just throw them in the Ford bin instead of the Chevy bin at the facility. No worries, toured many of them.


Sent from my iPhone using Tapatalk

 

[Hedgehog]

Maybe down the road the Ford parts will go away, right now they will have to prove to me that they are the junk many people say they are. This is a money thing, I've got'em, I'll wear them out then replace them with the GM stuff. Hopefully that won't be for a while yet.

 

[Hedgehog]

"The Whole Shebang" is here sitting on my counter. This is a BIG heavy piece of equipment, naturally there are no instructions. Generally I know how to install the thing, but it would be nice to have some instructions for how to properly fine tune it.

At first it wasn't obvious how the bracket should be installed. The bracket being the assembly between the booster and the firewall. I'm not 100% sure though, there is a pivot arm attached to the bracket, does that go toward the top or bottom? Then there is the push rod that attaches to the pedal. I imagine the right thing to do would be to measure the stock rod from the firewall to the pedal and adjust the new rod accordingly.

Once installed it seems fairly straight forward.

 

[Hedgehog]

Did a search, found some pictures, evidently the position of the pivot doesn't matter. Up or down, it's all good.