Outlier Disc Brake Conversion

1941 - 1945, MB, GPW modifications, sugestions, and ideas, official MWO's and unofficial WWII field mods NO EBAY or COMMERCIAL SALES.
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Outlier Disc Brake Conversion

Post by Outlier » Fri Apr 25, 2014 11:27 am

This is a documentation of how I modified my Ford GPW to have more modern disc brakes. It'd also apply to willys MB's and probably cj2a type jeeps.

When I get around to it, I'll write out how its done on a M38A1!

The goal is a cheap, easy and effective conversion, with straightforward, complete steps. Many people have done similar, excellent brake mods to their jeeps, but I found complete details lacking and frustratingly spread throughout many posts. Therefore, this is necessarily my own spin on a common mod :D

This conversion makes sense for people who want to change their jeep's stopping ability while decreasing maintenance effort - for roughly the same cost of all new drum brakes. 8)

Of course, I make no guarantees... I am mechanically inclined and love jeeps, but I'm no expert. This is just a record of what I did. I have no formal automotive training or certifications. Brakes are a major safety system on your vehicle. Research carefully and think critically before making any changes based on what I put together for my jeep. In using anything from me or info I've compiled, you assume all responsibility/liability for results!

With that out of the way, heres some background: I needed to make my jeep stop safer. So did a few of my friends. We could either re-outfit the old drums, or install discs. Rather than drive back into the difficulties, constant adjustments and marginal performance of drum brakes, we went with discs: easier maintenance and more reliable everyday service! One way or another, stopping ability is worth an investment. For us, a disc conversion for roughly the same cost as drum rebuilds sounded pretty good.

The secret is to use calipers and rotors from a GEO TRACKER or SUZUKI SIDEKICK. (Not a Samurai, and no 4-doors allowed.)

At the start, I did this to my jeep, Belac did it to his jeep, and my friend Lance did it to his jeep. All three work beautifully. Quite a few others have also done it. Since converting 6 years ago, I've driven my jeep in dirt, rain, mud, snow, as a commuter on the road in all conditions and extensively in the mountains. I have found stopping ability to be exponentially better than anything I could get out of the old drums. And I sure spent a lot of time fiddling with those!


So here it is!

#1: Parts list
Image

#2: Bolt List and Notes
Image


Notes: (Edited according to feedback from people who have completed the conversion)

*Wheel Clearance:
Original combat wheels will clear the caliper with the specified 1/2in spacer. Interestingly, reproduction combat wheels barely don't. Either of two things can be done to correct this:
1. Put a washer on each stud prior to installing the wheel, or
2. Grind the corners off of the caliper slide bosses.

*Calipers:
Left/Right specific. Easy to tell which side they go on, the bleeder valve must point up.

*Hoses and lines:
Secure all lines. It has been pointed out that this has not been done yet in the example install pics. Also, routing the front flex hose through the little hole on top of the knuckle is not advisable, as it will eventually wear a hole.

*Proportioning Valve:
Installed anywhere between the Master Cylinder and the rear axle lines. Adjust so that rear brake application is 50-60% of the front. (Rear shouldn't lock up before front)

*Residual Pressure Valve (RPV):
This is a little metal diaphragm with holes in it that is located in your Master cylinder. The RPV must be removed, so that your brakes don't drag. This is something I must do soon, but I have put it off because my brakes don't drag.

*Wheel Studs:
The new studs fit very tightly in the holes left by removing the old studs. I used a hammer to drive my old studs out of my hubs, which is evil and destructive, and requires tapping the new studs slightly with a brass hammer to get them to line up with the rotor holes. It has been suggested that drilling each of the rotor stud holes out with a 9/16 bit will make the rotor easier to install/remove.
Last edited by Outlier on Wed Oct 11, 2017 7:20 am, edited 15 times in total.
1943 GPW 121189
Engine #66098


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Re: Outlier Disc Brake Conversion

Post by Outlier » Fri Apr 25, 2014 11:30 am

Instructions: These are the steps I did for each wheel.

#3: Front End
Image

#4: Rear End
Image

#5: Final Steps
[url=http://www.surfacezero.com/g503/showpho ... ps&cat=500]
Image



Pictures:
Image

Front Left Detail
Image

Left Rear Detail
Image

Front Right w/ Spacer
Image

Front Right w/o Spacer
Image
Last edited by Outlier on Thu Oct 29, 2015 4:08 pm, edited 5 times in total.
1943 GPW 121189
Engine #66098

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Re: Outlier Disc Brake Conversion

Post by Outlier » Fri Apr 25, 2014 11:42 am

All this info is our small but happily free contribution to the enthusiast community. The only specialty piece is the adapter bracket. Every conversion we researched seemed to have a different bracket, so we kept the tradition: I developed my own so that I know it will work with my own specific procedure. The adapter bracket is not complicated, but it took a lot of effort to get the holes in the right locations.

Edit Oct '17: I am able to make these still: $35 ea, 10 bucks shipping. Just send me a PM. I am also open to trading jeep pieces, if that is more your style.

Pricing: I put together a few scenarios, just for reference. (these were accurate when I first started working on this in 2010)
#6: Pricing
Image


There you have it!
Last edited by Outlier on Wed Oct 11, 2017 7:30 am, edited 6 times in total.
1943 GPW 121189
Engine #66098

VitoCapo
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Re: Outlier Disc Brake Conversion

Post by VitoCapo » Fri Apr 25, 2014 3:11 pm

I went to your pictures link on surfacezero, could we maybe get some details on the brackets?
I assume they're custom made. Everything else looks readily available and you did a great job on the instructions.

Thanks!!!

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Re: Outlier Disc Brake Conversion

Post by Marty, SoCal » Fri Apr 25, 2014 3:33 pm

Any pictures?
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Re: Outlier Disc Brake Conversion

Post by VitoCapo » Fri Apr 25, 2014 9:04 pm

Marty, SoCal wrote:Any pictures?
Here's Outliers Pics on SurfaceZero. (If you want me to edit them out Outlier let me know. They're just really useful!)
Just to be clear... not my pictures.

Image

Image

Image

Image

Image

(done and done, and your Jeep looks great :D )
Last edited by VitoCapo on Sun Apr 27, 2014 10:25 am, edited 2 times in total.

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Re: Outlier Disc Brake Conversion

Post by Outlier » Sat Apr 26, 2014 6:15 pm

My own jeep isn't exactly a beauty and is heavily used, so I was reluctant to showcase the install on it. My friend Lance however, did a beautiful job. I was waiting to use some pictures of his installation, which I was able to get this afternoon. If you would like to see more of his work, he gave me permission to link to his blog: http://lancesjeep.blogspot.com/2013_01_01_archive.html
I've edited the original posts to include a few pictures of his brakes.
1943 GPW 121189
Engine #66098

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Re: Outlier Disc Brake Conversion

Post by bazza46 » Fri May 09, 2014 4:18 pm

Is the pedal pressure low enough without a vacuum booster? Disc brakes don't have any self-energizing action.
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Re: Outlier Disc Brake Conversion

Post by Outlier » Sat May 10, 2014 12:39 pm

I would say the pressure you have to put on the pedal is slightly less than for ordinary drums, maybe it works this way because the calipers are so small.
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Re: Outlier Disc Brake Conversion

Post by bazza46 » Sat May 10, 2014 2:28 pm

Sorry. Do you mean 'less than you'd have to push on MB/GPW brakes', or 'less than most drum brakes on cars'?

The reason I ask is that the thing I find most annoying on jeeps is how hard you have to push the pedal to stop, especially if you want to stop fast.

I'm not concerned about brake fade, as I don't go racing around, using the brakes so frequently that this would be a problem.

I've got a pretty strong leg, and so can almost lock the wheels in an emergency, but I'd like the easier feel, like in newer cars.

I hear that a vacuum booster reduces pedal pressure considerably, but of course, does nothing to cure brake fade. Discs are to most purposes, fade proof.
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Re: Outlier Disc Brake Conversion

Post by Outlier » Mon May 12, 2014 1:18 pm

Yes, I was comparing to GPW/MB brakes. The jeeps with this conversion stop faster and with less total application of the brakes than they previously did. Of course, adding a brake booster would certainly make pedal pressure less, and I've seen a local CJ2a that had one successfully added, but doing that for this conversion would significantly up the price and complexity, so we left it alone.
Last edited by Outlier on Mon May 12, 2014 4:23 pm, edited 1 time in total.
1943 GPW 121189
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Re: Outlier Disc Brake Conversion

Post by bazza46 » Mon May 12, 2014 3:38 pm

Thanks. I really don't want to add abrake booster because it makes the engine compartment look so much less original, but the disc brake setup looks so natural and unobtrusive. For better stopping power, that's the way I'll go.
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Re: Outlier Disc Brake Conversion

Post by pkozak1 » Tue May 13, 2014 6:23 am

Good morning Sir, I am very interested in your conversion. I emailed and pm you about purchasing your mounting brackets.I would love to rap up my rear axle rebuild but now that I have read your post, I want to install disc brakes. I just need your mounting brackets. Can you sell me four of them, and do you also sell the 1/2 spacer plates as well? Please pm me or email me (pkozak1@rochester.rr.com) with your address and what and how much total with shipping, my zip is 14414 if you need it for shipping calculation Thank you for your time, Patrick.

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Re: Outlier Disc Brake Conversion

Post by pkozak1 » Tue May 13, 2014 6:42 am

Whats your oppinion on just your disc brakes on the front axle only? If you put the discs on the front axle and left drums on the rear axle, could you put the one inch wheel cylinders (new) from the front axle on the rear axle for more stopping pressure?

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Re: Outlier Disc Brake Conversion

Post by Outlier » Tue May 13, 2014 7:07 am

Hello pkozak1, I replied to both your email and PM, or at least I thought I did, I will check!

As far as a front-only upgrade, that is totally fine. I developed this conversion on two jeeps at the same time, and had some difficulty finding 8 donor calipers at once. I actually ran front discs only, on my personal jeep, for nearly three months. My rear axle was completely set up and ready to go with the brackets, just missing the calipers, with plugs in the rear junction block. (= total absence of drums or any rear braking) When I found two more calipers, it took about 15 minutes to bolt them up and remove the plugs. But even when I only had front brakes, I had no problems with stopping ability. Our jeeps are not that heavy, and the calipers are designed for a vehicle of similar size and weight, with most of your stopping power coming from the front anyway due to weight transfer.

For moving the original larger wheel cylinders from the front to the rear, hopefully someone else will chime in. Seems to me like there wouldn't be a problem, as long as the shoes still fit. Are the front cylinders larger only in diameter, or are they longer too? ...I don't believe in drums anymore, so I have none to look at to compare :lol:
1943 GPW 121189
Engine #66098


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