1971 cj5 brake conversion

I just purchased a 1971 cj5. It is all stock. My question is, I want to change the brakes. I want to put 11" brakes on the rear and disc brakes on the front. Do I need to change the brakes lines or are they fine? Do I need to change the master cyilnder of is it fine? Are there any things I need to add to make the conversion work well? Any recomendations would be helpful. Which front disc brake kit works the best?

Thanks Julius

 

I would assume that 1971 still had floor pedals, is that correct?............11" Drums in the back are a normal upgrade and there are numerous front Disc's kits that can be used. Chances are the brake lines in the rear will not get to the larger brake backing plate. In the front the rigid brake lines come off of a block on each side so just the rubber flex line would need to be changed.
If you still have the frame mounted single original Master cylinder then a later 2 chamber cylinder needs to be installed..............Herms Overdrives and R&P 4 wheel drive both sell a two chamber frame mounted conversions for that Master cylinder.........you will also need a proportioning valve. Both vendors mentioned above also have 11" rear brake kits and front Disc kits.................you could also source those Disc kits used off of a 77-84 Jeep CJ5 that were factory equipped.

 

Wow thanks that was very helpful. My plan is to change the brakes and then go to power steering with a saginaw box and an sm465 tranny. Oh and by the way the pedals go through the floor.

Julius

 

My 70 has the dual chamber master from the factory. I would bet that a 71 would too. I think the proportioning block is there too.

 

Julius................while your at it consider doing a Dana 30 front end......they can be sourced or found with factory brakes disc's although it may require a gear change to match your rear......the early narrow track D-30's have the same spring width and will bolt right in.........it is 3 inches wider overall which is great for an early CJ........makes a nice complement to your Saginaw Power steering.....which by the way will require overhauling or replacement of your steering column and perhaps a change of the exhaust system on the drivers side of the motor......................depending on what motor you have.

 

The chamber size and bore for the Disc / Drum versus the Drum/ Drum Master Cylinder are different.

 

It is a very good idea to change the brakes of a 71 CJ5, because it is sometimes difficult to stop in line. With disc brakes in front, it must be very pleasant and safe to drive. :twisted: I would be able to do it but I think t is better to ask to a pro, with a guarantee. How much does it cost in US? There is not so much work.

 

Alan, Best to do the 11" drums in the back , with a Disc setup up front. Its not that hard as an upgrade here but perhaps in France it may be harder to source parts.......Mostly all is just Bolt-Up! Here we can get parts off of existing Factory equipped CJ-5's used...........but there are numerous aftermarket guys putting kits together that would probably ship them your way...........Look at R&P 4 wheel in Oregon or Herm's Overdrives or any of the other 4-wheel parts house's on the internet. Another good source is the street rod community as all of this Disc brake stuff is GM based and for the most part it is the mounting bracket that is vehicle specific............... If you went to 11" brakes in the rear the hard lines may have to be extended, and disc's in the front the rubber flex line would also need to be changed..............Master Cylinder & Proportioning valve would also need some attention or replacement. Disc brake kits $400-500 Rear 11" Drums $350.........a new master cylinder and Proportioning valve another $150.............I'm just guessing from memory.

 

Alan, i did the same disc brake conversion on an m38a1.
I used suzuki vitara disc brakes and rotors from 2.0L V6 and power brakes from vitara.
I also change the pedals, i can post a few pics from the set up. I think is a lot cheaper and easier to find vitara parts in France as in Greece.
Of course you must find a machinist to make the disc brake mounts for the spindles.
Also i can provide you all the drawings i used to build them.

 

Original style MC will work just fine. Went to Chevy discs many years ago and have had no issues with MC.

 

Alan28 i don't want to hijack the thread so i will start a new thread about disc conversion with alternative parts.

 

Thanks for all these infos. When I was young I welded myself the metal brake (pipe) line, I believe now that it was not a good idea. So, about brakes, I prefer to have it done by a pro. It is a question of money. We have in France some specialists and they can do it. I just have to wait and save money.
The fact is that the CJ5 brakes are not top level.I can say modestly that I am a good driver, I was able in the past to drive - as probably many of you Jeepers did- the kind of machine (car, truck, motorcycle) crazy to travel with. But now, regulations are more and more strict, and this is not good to do this.
SO as soon as I can afford the good brakes system, I buy it.

 

I just got done taking the body off of the frame and checked the master cylinder and it is a dual chamber as well as has the proportioner valve. I plan on putting new brake lines on it also.

 

If you don't change the master cylinder to a disc brake mc, pay close attention to the calipers after releasing the brake pedal. Ensure they release completely and there is no residual drag on the brakes. If you get drag after applying the brakes and releasing, change the master cylinder. As previously stated, they are different. Differences in piston size ratio may affect proper release.

Bill

Sent from my DROID X2 using Tapatalk 2

 

The master cylinder bore size will not effect brake release, only apply. The residual pressure valve in the master cylinder can effect release as its purpose is to hold pressure on the hydraulic system. Typically if using a drum brake master cylinder in a disc brake application The residual pressure valve needs removed and a 2 lb unit for disc brakes needs installed in the brake line. A 10 lb unit is typically used for drum brakes.


Sent from my iPhone

 

Lets clear this up as there is still some confusion here...............Nick is correct that the cylinder bore size will not effect brake release and only appy......................and also correct that the unit needs the correct residual valve............but make no mistake a Drum/Drum master is not correct for a Disc / Drum conversion.............simply because the Disc side of the system takes more volume than the drum side........Why? Because the Pistons in the calipers hold more fluid / volume and travel farther as the Pads wear down so it needs more fluid in the line / system to compensate for wear as compared to the drums that have a relatively small wheel cylinder and very little travel.................Some master cylinders even have stepped bores.
Just make sure during your conversion that you have the correct Master to support the system your building.

 

When i did the conversion, i did it the opposite way.
What i mean is, because i wanted to get rid off the wear out under floor pedals and clutch,
i first changed the master cylinder with power boost brakes which went on the engine side of the firewall with hanging pedals and then i did the disc brakes.
I didn't want to do the discs right after the pedals.
hat i saw is that the new master cylinder despite it is 1" bore it needed the whole pedal travel to make the drums stop and when they starting to stop they where locking right away.
That make me think(after i finished the whole conversion) that the OEM master cylinder had RPV.
When i did the discs the pedal travel was reduced at least to half, because the brake caliper might be a lot larger than the wheel cylinders
but the movement that makes is a lot less and they are almost always in contact with the rotor.
But after the discs that i got a better pedal i had the filling that something was wrong with the rear.
The discs where engaged when i was pressing the pedal but the wheel cylinders didn't untill i put in line an RPV.
Now i have a low travel soft pedal with a lot of brake power. One of the best conversion i ever did for safety.
Just my experience.

 

Here is a reprint from Master Power Brakes Tech page on line about the difference's regarding a Drum/Drum Master versus a Drum/ Disc master[TABLE="width: 619"]
[TR]
[TD="width: 595"][h=1]Reference/FAQs: Master Cylinders[/h][/TD]
[TD="width: 13"][/TD]
[/TR]
[/TABLE]
[TABLE="width: 619"]
[TR]
[TD="width: 11"][/TD]
[TD="width: 595"]How does a disc brake master differ from a drum brake master?
A drum brake master will differ from a disc brake master in two ways. The amount of fluid that a drum brake master has to move is less than disc brake. Drum brake masters have 10 lb residual valves at the outlet to keep a residual pressure on the drums. If you use a drum brake master for disc brakes you would move an insufficient volume of fluid and the disc brakes would drag because of the residual valves.
[/TD]
[/TR]
[/TABLE]
Now of course you can use a 2 lb residual valve and cancel the drag , but still not solve the lack of volume needed to supply the half of the system that has the Disc's...........furthermore most if not all residual valves started to disappear in the 1980's as wheel cylinder cup expanders came into play which kept air from entering past the cups...........Residuals are now never used in a modern system......point is if someone is upgrading and using modern components like calipers perhaps that need then goes away...............One should first understand what components or parts they are going to use. Then reference the compatibility between these parts to build the system correctly.
My only point here is Safety!

 

I also am doing the power /disc brake convert ...... I have a Dana 27 front axle !
The info I have so far is : GM Dana 44 1/2 or 3/4 ton front axle backing plates ,....Rotors 1977-78 Jeep CJ and 1974-80 International Scout II,5x5".5 Bolt Pattern-5 Bolt Holes-11.75" Diameter-2.81" Height-1.19" Thick-3.76" Center Hole Diameter- for 6 bolt caliper mounts,...... and 1971-78 Chevy/Jeep Wagoneer DISC BRAKE CALIPERS for dana 44...These calipers fit many 1/2 ton & 3/4 ton Chevy/GMC trucks with dana 44 & 10 bolt front ends, and also fit Jeep Wagoneer, J10 & J20 pick-ups.
also picked up a complete master / booster , and bracket w/ proportioning valve !

Just need to get all the pieces !