Sunday, May 6, 2012

Rear Disc Brakes

I have a confession: I am terrible at adjusting brake drums. No matter how many times I try, I always seem to end up with dragging brake shoes or non-functional brakes. In the blue-moon chance that I get a brake drum adjusted properly on my car, it's a sure bet that I won't be able to repeat that on the other side.

There. I'm glad to have gotten that off of my chest. Phew.

So, in order to circumvent my Krypton-like resistance to brake drums, I took the entirely rational step of replacing them with an over-engineered technological upgrade: disc brakes.



The parts collection includes the following:

Discs from the front of a Mk1 VW Jetta/Golf
Carrier brackets from the rear of a Mk3 VW Jetta/Golf
Calipers from the rear of a Mk4 VW Jetta/Golf
Pagid brake pads for VW Mk4 Jetta/Golf rear brakes
Rear brake lines from a VW Mk4 Jetta/Golf
Brackets from Jake (http://classicdaily.net/)
6X M10 X 1.5 X 20mm Allen Socket Cap Screws
2X M10 X 1.5 X 20mm Flat (Countersunk) Allen Screws
4X M10 X 1.25 X 20mm Allen Socket Cap Screws
4X M10 X 2mm thick washers

I also had the wheel hubs turned down by Tom at www.02Again.com to fit inside the new discs.

First, I bolted the brackets to the trailing arm. You have to grind out a piece of the shock boss support to get the bolt in, and you'll likely do a better-looking job than I did.



The bolts are the 1.5 pitch allen heads and the flat-headed countersunk bolt.

I used a regular-head bolt for the bottom mount because the hardware store only had two of the fine-thread (1.25) M10 allen head bolts. It would have looked a lot cooler with matching bolts, for everyone that climbs under my car. Looks like I'll be waiting another year for that Ridler.

Also, here's a fun fact: You'll need 15" wheels to fit over these brakes. So, if you have a set of 14" E30 Steel wheels, you'll need to do a little clearance grinding on the calipers. Have fun with that.


Here you can see the few millimeters of clearance between the wheel and the caliper.



When you bolt it all together, put the 2mm thick M10 washers between the bracket and the carrier.


A note about the carriers:

When researching this conversion, I kept coming across the requirement for Mk2 Jetta/Golf carriers. Since I bought the discs, calipers and carriers from a single person that had collected them from the salvage yard, I had no way of verifying the donor car parts source. So, I ventured to the salvage yards to verify, but I found that I could rarely find a Mk2 Jetta or Golf. The few that I did find had drums in the rear, so I was confounded.

Then I pulled a rusty carrier from the rear of the much more common Mk3 Jettas and Golfs. The Mk3 carrier was identical to the supposed Mk2 carrier that I bought. This mean one of two things: either the original parts requirement is for Mk3 carriers and not Mk2 carriers, or the Mk2 and Mk3 carriers are identical. Either way, you can safely assume that Mk3 carriers will work.

For the brake lines, you'll get them looking like this:


Bend them until they look like this:


The advantage to using these lines is two-fold. They replace the hardline that goes along the trailing arm, eliminating one connection (read: leak opportunity) and they have a banjo bolt connection to the caliper, which is a lot easier to thread into the caliper than a hardline. 



Sidenote about the Pagid brake pads: The used calipers came with used pads that had these little shims to keep the pads in place. The Pagid pads did not come with the shims and actually didn't need them. It's a detail, but I can imagine someone getting confused about trying in vain to shove pads in with these shims in place. If you were actually able to do so, the pads would never move.


I used stock emergency brake cables. They work fine, but as I discovered, need 30-35mm of spacing to work properly. I had to improvise with a few spare m10 and m12 nuts. Maybe I'll remove and paint them later, you know, to stay in contention for that Ridler Award.


So, after bleeding them (without having to remove the caliper - woohoo) and adjusting the emergency brakes, I've got self-adjusting, way-overengineered brakes. Now that I have the ability to stop, on to obtaining the ability to go.

UPDATE: Those spacer-nuts are hideous. I have since made a proper spacer that does the job as looks much better. See here: http://tx02.blogspot.com/2012/05/front-swaybar-wiring-finished-wipers-on.html

One more note: The discs have a countersunk hole for a flat-head allen bolt to hold the disc in place when the wheel is off. Since the disc is now mounted on a turned-down BMW hub, there is no threaded hole. However, I might drill and tap this hole just to regain the intended though unnecessary feature.


6 comments:

  1. All you need is a wet road and a little bit of play with a proportioning valve and you'll be set

    ReplyDelete
  2. Commento numero doso. You mention drilling and tapping a hole in the hub for the countersunk hole in the disk. Drill two at 180* from each other... that way you can remove the bolt from the hub on one side and screw it in to the hub from the back side 180* opposite. This pops off the disc no matter how frozen it ends up being. Just a tip.

    Jay

    ReplyDelete
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