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Just Some Dude in Jersey
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Discussion Starter #1
This is my thread about attempting to install VW rear disc brakes on an early style 3:18 rear axle from a 1968 Kadette Wagon w/ auto tranny on one of my GT’s.

First off, installing rear disc brakes on an early c-clip equipped axle is not normally recommended due to the back and forth “float” of the hub on this style axle. A quick check of the play in the axles before I disassembled it showed that this axle assembly is in very good condition and both axles have less than a match pack’s play to them.

A discussion about doing this mod to this type of rear axle a few years back kind of came to the conclusion that I could probably get away with it, if I don’t subject this rear to hard driving/racing, which I won’t. I had a question brewing about what to do about the sheet metal “bearing retainer plates” that both styles of rear axles have, but I now seem to recall that I may have to remove them entirely. Theoretically, if the c-clip comes off the axle, then the axle can just slide right out of the rear. The bearings ride right on the axle in these early rears. The axle ITSELF is the inner bearing surface. Take the c-clip off and the axle slides right out, even with the bearing retainer plates in place. On later rears, the bearing is a self contained unit, with inner and outer bearing surfaces, and the axles are held in place in the diff by big sturdy nuts rather than c-clips. I need to use this type of rear because it is the only one with a 3:18 gear ratio to extend the range of the 3sp auto tranny set ups I have in both my cars. It turns out that putting disc brakes on this type of axle potentially adds an extra element that would prevent “axle loss”. The brake caliper’s outer pad would prevent the axle from sliding out of the axle housing if the c-clip comes off. There is nothing to stop an early axle from falling out if the c-clip comes off when equipped with the oem drum brakes.

Feel free to correct any assumptions and bold claims I make in this thread.

The black L-shaped adapter bracket that you see in the pics below was purchased a few years ago off of German ebay and it is made for the later style axles. Early axles had two of the brake backing plate mounting bolts closer together. You can see in one of the following pics that the hole pattern doesn’t match my early style axle’s holes. Only two of them line up. I tried fitting this adapter bracket to my later style ’72 rear and, although the holes line up, the arc cut into the bracket hits the bearing retainer plate. Based on this and a vague recollection of the previous discussion of this mod, I am assuming that to do this mod the retainer plates must be removed. Since my brake adapter won’t work with this axle, it would probably be best if I made my own brake adapter bracket specifically for this type of axle, rather than weld and cut and modify the other adapter. If I’m clever and talented, I may even be able to design it so that the retainer plate can stay in place.

Can some of you help me with info on this mod and point me to threads pertaining to it?

I got the part numbers for this mod from Gary several years ago. As I understand it, these are VW rear disc brakes with rotors that may have come from a Buick Regal or something. Gary, please clarify. I have shown pics of the part numbers on the boxes. They have just one piston that pushes outwards. I goofed when I ordered the calipers and should have bought pre-loaded ones with the pads and the hardware. Do these brakes have an outer pad? I can’t for the life of me figure out how the outer pad would be held in place. Is there just the one pad pushing from the inside outwards?


The questions above and the pics following are as far as I’ve gotten with this project. I still have to flush out, clean, and seal up the rear and I need 2 new axle seals. Harold?

Your helpful and insightful comments and suggestions are welcome.

Your withering condemnation, insults, and ball busts are also welcome.









 

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Just Some Dude in Jersey
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Discussion Starter #2
More pics:

Pic of rotor and adapter bracket with later style rear


Another angle showing roughly how things line up


Pic of later style axle brake adapter bracket loosely fitted to my early style axle showing the bolt hole discrepancy:


Assembly loosely fitted to the early axle for visualization


The levers and stuff you see under the word “supposed” below are the parking brake actuating assembly of the brake calipers. Is this how you orient them, with the cable running below the coil spring buckets?
 

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Gordon, I have to say that you're one amazing dude.

Most people who had a setback like the one you had with your engine after putting that much effort into it would have locked up their workshop and walked away in disgust and let let it sit for a while while gathering themselves up again.

Not you, you just find something else to work on, one project after another. I wish I had your drive Gordon, I really do :cool:
 

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Just Some Dude in Jersey
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Discussion Starter #8
Hay, I would rather he put his Extra energy into improving our cars, Instead of out on the SHOOTING range, He does work for the USPS :haha::haha:
My boss took all my ammunition away. He said I misused it. :sigh:


Gordon, I have to say that you're one amazing dude.

Most people who had a setback like the one you had with your engine after putting that much effort into it would have locked up their workshop and walked away in disgust and let let it sit for a while while gathering themselves up again.

Not you, you just find something else to work on, one project after another. I wish I had your drive Gordon, I really do :cool:

Well, gosh, thanks for the compliment!

Honestly, I keep my irons in the fire because of you guys. You're a great audience.

Also, you know how it is, the longer you let a project languish the harder it is to get started again. I should have started this project no later than last Winter, but I sat on my hands and didn't do squat.

:veryhappy
 

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Do these brakes have an outer pad? I can’t for the life of me figure out how the outer pad would be held in place. Is there just the one pad pushing from the inside outwards?
Gordon; Yes, there should be an outer pad. You place the outer pad in the appropriate slot and place the inner pad in its appropriate slot(and in the piston with a retainer spring) Take the entire assembly and place it on the rotor and mount the caliper with the appropriate hardware, usually two bolts for the pads to slide on and two bolts which connect it to the axle mounting bracket. The rotor will keep the pads in place.

The pads will probably look something like this (my Saab rear brakes) scroll down to see brake pads.

2001 SAAB 9-5 SE 3.0L 6 Cyl (24 Valve) Turbo Rear Brakes Parts - Free and Free Shipping


A single piston caliper is normal for cars nowdays. My Saab is set up this way, front and back.
 

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Gordon, before I changed rear ends I had discs on my early axle which worked perfectly and I can assure you that you are going about it correctly. Disc brakes work fine with C clip axles as long as you have floating calipers, which you do. As you already know on the early axles the sheet metal plate does nothing to retain the axle but if memory serves it does help to retain the seal which doesn't require much. So if you need to modify it to work with your bracket that is acceptable. You will need to trim your bracket to fit. Once that is done install the axle with the C clip in place, install the disc with a couple of lug nuts to hold it in place. Place the pads in the caliper and slide it over the disc and see if it aligns with your bracket. If it does all is well, if not spacer as required to keep it centered on the disc.
 

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Your Noble Friend ;-)
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Just Some Dude in Jersey
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Discussion Starter #13
Thank you gentleman for the explanation and pics. All is much clearer now! Jeff, thanks for finding that list of related parts I still need.


I think those brackets I bought are mis-manufactured. Or made for a different Opel. There is no way that the arc that is cut into it can fit around the casting of the axle housing if mounted on the diff side of the mounting flange and, as the previous pic of mine shows, it intrudes into the spinning axle area when mounted on the outside of the mounting flange. I may be wrong, I'll investigate later......

Regardless, I have to make my own mounting plate anyway to match the older axle style's bolt pattern.
 

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Just Some Dude in Jersey
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Discussion Starter #16
Tonight I whipped up a diagram for a rear disc brake adapter bracket specifically for early c-clip style rear axles. Dieter was correct that the adapter needs to go on the diff side of the flange, not the wheel side as I had it in my pic. Could you make a bracket that fits on the wheel side? Yes, but it would be a lot more work to make for minimal gain:






I checked the diameter of the axle housing casting on both my early and late style axles and they are both about 3 1/16” in diameter at the flange bolt holes. Therefore I decided that the arc carved out of the bracket should be 3 1/8”. The axle flange has special bolts in which the head of the bolt is flush with the bolt on one side. This is because the holes in the flange are just 1/16” from the axle housing I measured. As you can see in the pic above, the bolt holes are right up against the arc that needs to be cut to clear the axle housing.

Using the other bracket and a bunch of transposing, interpolation, and cross-referencing and other fancy words, I determined that the brake mounting holes need to be 2 13/16” from the center of the axle. The brake mounting holes are 3 9/16” apart from each other.

Gary offered to make this bracket for me, so I’m going to make some copies of my full scale drawing and send them to him. I’ll save the original and copies in case any of you want your own.


This project now goes on the shelf until new seals, a replacement c-clip, brake parts, and a few other things get cobbled together……..


:veryhappy
 

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Just Some Dude in Jersey
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Discussion Starter #17
Houston, we have a problem......

I had a little time to kill today at work today, so I banged out a mockup of the bracket out of a piece of scrap 3/16” aluminum. I needed to verify that my bracket design would work and especially if the calipers were mounted the proper distance from the axle center to to work with the rotors I’m using:



I got pads today, installed them in my calipers, and mounted everything to the axle:



Uh-oh. Houston, we have a problem. The calipers just barely fit with 1/16”-1/8”” of space between the outside of the rotor and the caliper. The brake pad is well positioned at 1/16” from the edge of the rotor.

But…..

…the edge of the pad closest to the hub extends WAY too far, all the way past the relief groove, until it actually hits the cylindrical part of the rotor. So much so, that I can’t actually get the last bolt in that holds the brake onto my plate:








See next post……..
 

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Just Some Dude in Jersey
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Discussion Starter #18
So what to do? I think that I must have gotten the wrong type of pad for this mod set up. I need a type with at least ¼” less height. Can one of you guys who has done this VW rear disc brake mod show me or tell me what part number shoe you use?


Or should I take a hack saw and grinder to my brake pads to get rid of that extra material?:

 

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Your Noble Friend ;-)
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I took one of my calipers off and took some pictures.
My parts list is in the other thread, see the link in my post above. My Audi disks are about 240-245mm dia, and have a brake area of a little under 50mm / 2" wide.
Your caliper number shows at Advance Auto Parts to fit a 1995 Golf VR6 (and numerous other VW years and models). Therefore, it looks like you were sold the wrong brake pads. Do not grind them off, go back and get the right ones!

Dieter

Edit: Your brake pads look the same as mine, measure your disk size!
 

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