(4/10/2004) - If you are like me, you have been drooling over rear disc brake conversion kits for a while. If you are seriously considering this modification, look no further than CB Performance's "Race Strength" rear disc brake conversion kit, available at aircooled.net. Before we get into the install (which is fairly straightforward by-the-way) lets discuss this kit. Some of my prerequisites for picking a rear disc conversion kit were that: it had to include nearly everything to do the job (minus the beer, tools, and brake fluid), it had to be composed of quality parts, and the kit also had to be reasonably priced. I'm sure you've all seen the MEGA-expensive Porsche disc brake conversions... While they look and perform good, the cost doesn't necessarily justify the purchase (do you really think brakes that big are necessary on a car that weighs less than ton?). Don't get me wrong, I'd love to have some for my car (anyone have a set they want to give me? <grin>), but for the most part they are overkill, and way too spendey.
Another note: If you are considering this rear disc conversion kit and you have not yet converted your front end to disc brakes, I HIGHLY encourage you to purchase the front disc brake conversion kit FIRST!! Why? The absolute largest difference in braking can be made for LESS money by putting discs on the front end first. You almost always want to convert the front end first, then the rear end. Front disc brake conversion kits can also be found at aircooled.net.
Discs vs. Drums what's better?: Since you are here, I will assume you understand why disc brakes are better than drums. There is so much to consider I could write a thesis about this topic, but I will sum it up quickly for those who are interested. Brakes work by turning rotational motion into heat. When you depress the brake pedal you are putting a force onto a brake pad (in disc brakes) or brake shoe (in drum brakes). The pad/shoe is typically made of a material with a large coefficient of friction. The harder you push on the pedal. the more friction you create between the pad and disc (or shoe and drum). This causes the rotational motion (kinetic energy) to turn into heat (thermal energy), effectively slowing your vehicle down. There are MANY MANY things that can increase or decrease the effectiveness of brakes in general, but the largest factor in how well brakes work comes down to how well they can dissipate heat. Drum brakes tend to retain heat (due to the "drum" design), and eventually they can become saturated with heat and cannot absorb more. This can cause you to loose a lot of your braking power (AKA: "brake fade"). Disc brakes have a large advantage because the heat is not "housed" inside the drum; it is exposed to the air flowing around it.
I installed this kit on my 1974 super-beetle, therefore this article is meant for I.R.S rear ends only. Swingaxle installation will be slightly different.
So what all do I need? If you have done a brake job before, you should have all the tools you need. Specifically, you will need the conversion kit, brake fluid, a little grease, and some tools. I would suggest you read this article well before you plan to install the kit, so that you can be sure you have everything you need.
Hooray, It has arrived - Lets get started!
Once you receive your kit, you should start off by inspecting the box of parts and making sure nothing is missing or damaged. In this section I will identify all the parts, and the quantity you should have received.
Below are the rotors (2):
These are the calipers (2):
Here are the hubs (2). Notice that the studs are the high quality PRESS in studs (VERY nice!), NOT the cheesy screw-in types:
These are the aluminum caliper brackets (2):
These are the emergency brake cables (2):
These are the new hard brake lines (2). Don't worry if they arrive to you straight, or bent - you will be bending them to fit the rear of your car anyway:
Here's all the hardware which I will detail below:
#1) These are the Axle bearing retaining shims. They go inside the bearing seal retaining cap (explained later in document). You should receive 2.
#2) These are the Axle Spacers. These will go on after the hub and rotor are installed, and before you put the axle nut on. There should be 2 of these.
#3) This package contains the hardware for the caliper installation (4 bolts, and miscellaneous washers/spacers). This package also contains the c-clips for the emergency brake cable (there should be 2 c-clips).
#4 AND #5) These are the "seal kits." Each one should contain 2 bearing seal gaskets (you will only need to use ONE per seal kit), 1 new axle seal, 2 o-rings (one large and one small; you will only use the large one), and 1 washer.
#6) These are the lug-nuts that come with the kit. If you currently use drums with lug-bolts, you will need these. If you are currently using studs and lug-nuts, your current lug nuts should fit if you want to use them.
#7) These are the brake pads (there should be 4 in the box).
Prep: One thing that I learned when I did the front disc brake conversion was that it is very beneficial to paint the hub-section of the rotors to keep them from rusting (nothing looks worse than a set of nice brakes with rust all over!). Many will probably argue to NOT paint them because "you will be adding another layer of insulation to the brakes (bad)". Well, its either a thin coat of paint, OR rust. Rust can be just as good (or better) of an insulator than paint - so its your choice! For the rear disc brake kit, I decided to go ahead and paint the hub-section of the rotors and the individual hubs. The hubs already had a black coating on them, but I decided it wouldn't hurt to give them a little more.
The whole painting step is optional. But if you want to keep your brakes from looking like the one below, it is worth it.
You will notice that out of the box the rotors and hubs are oily/greasy. This is to keep them from rusting. The first thing you want to do before painting is to thoroughly clean them. For this, I prefer acetone and a lint free rag. Acetone cleans well, and leaves no residue - so the paint will stick well.
This is the Hi-Temp paint I used. It seemed to work well on my front discs, so I decided to use it again. Its available at Pep-Boys or equivalent.
On the hubs, I slipped some old fuel hose over the studs to keep from getting paint on them.
I like to use flat black and clear (pictured above) on the rotors. You want the black on the hub portion, and the clear on the friction portion. The easiest way to do this is to spray the hub portion as best you can, and when you are done wipe the excess black off with a rag soaked in acetone. You WILL have overspray if you don't mask (see pic below), but it is very easy to wipe off the overspray with the rag. After the black dries, clearcoat everything (including the friction surface of the rotor). PAINT THE FRICTION SURFACE, ARE YOU NUTS!?!? Nope, there is a reason for this; bear with me for a minute. If you take a look at the brake pads, you will notice they do not use the ENTIRE friction surface on the rotor. What you want to do is to paint this small portion of the rotor where the brake pad doesn't touch so that it wont rust. It would be a royal pain to determine where this area is exactly, so the easiest way to get around it is to paint everything. After the brakes are installed, the paint where the brake pad contacts will wear off pretty quickly, and the portion of the friction surface that is not in contact with the pad will still have paint over it - Voila, no rust!
When done, you should end up with something like this (painted on BOTH sides):
NOTE: It would be best to paint everything at least a few days before the install (preferably a week) so that the paint will be dry.
Time to install! I will assume that most people reading this article know how to pull the rear wheels off. (PLEASE use caution when working on/under a vehicle!). Lets get those old drums off of the car.... Chock the front wheels, loosen the lugs while the car is still on the ground, and put the rear end in the air.
With the wheel off, and the rear end up (and the car on jackstands), the first major thing that needs to be done is to remove the castle-nut holding the drum in place. This can be tough, as the nut is torqued to the neighborhood of 250 ft lbs!
First remove the cotter pin that goes through the castle-nut.
Next you will want a breaker bar to loosen the castle-nut. Your e-brake will probably not be strong enough to keep the drum from turning, so you can make a very simple tool out of a piece of angle iron (pictured below). Just drill a hole in it that will fit over a stud (or screw a lugnut into it) and then you can remove the castle-nut without the drum spinning on you. (And by-the-way: I have yet to damage any studs/lugbolts using this method.)
Success!; castle-nut removed:
With the castle-nut removed, you can try to pull the drum off. For me, it came right off - if it doesn't come off for you, use the adjusting stars (accessible from the backside of the backing plate) and loosen them up a bit. Below is what you will find once the drum is off.
Next, you will want to remove the backing plate. You can remove all the individual pieces if you want (springs, shoes, etc) - but you can save a little time, and keep all your old parts together by just removing the backing plate with everything still attached.
The first step is to disconnect the emergency brake cable (red arrow below). You may have to wiggle things around a bit, but it should come off.
Next you need to remove this bolt from the back side of the backing plate that holds the cable in.
Then you can unclip the cable from the lower shock mount (red arrow).
Now you need to disconnect the hard brake line running to the cylinder (on the back side of the backing plate). If/when possible, use a flare nut wrench (2nd picture down) to disconnect the line. Be aware that when you disconnect the line brake fluid WILL drip out (be prepared!). You will also be introducing air into the system, but this wont be a problem as you will have to bleed the brakes when you are done installing.
Now remove the four bolts holding the bearing seal retaining cap on.
When you pull the bearing seal retaining cap off (below), the axle spacer (2nd picture below) will probably also come off with it. If it doesn't, you can just slide it off the stub axle.
Now the backing plate should come right off with all the hardware included (you may need to fish the e-brake cable through the backing plate first).
This is what you should be looking at after removing the backing plate:
Remove the boot that goes over the e-brake handle inside the car. To remove the old e-brake cables completely, you need to loosen and remove the jam nuts (red arrows). Now you should be able to pull the cables out from the rear of the car.
You can also remove the short hard line since you will be replacing it with the longer ones that come in the kit. (I capped of the flex-line to keep brake fluid from dripping all over the place).
Now you can clean off the stub axle/bearing a little. Open bag #4, or #5 (refer to pic at beginning of document), and pull out the washer. Lightly grease both sides of it (general purpose wheel bearing grease) and slide it over the stub axle as show in the second pic below.
Now you can work on the bearing seal retaining cap. You need to pull out the old o-ring (red arrow), and you also need to pull the grease seal. The seal was a PITA to get out for me - it eventually came out though. A good seal puller should do the job.
Once the seals are out, you can clean the bearing caps. When done, you should be left with something like this:
Now you can pull a new seal and o-ring from bag #4 or #5 (refer to pic at beginning of document). Liberally grease up the new seal, and drive it in. I use a seal installation tool and a hammer, but a 2X4 and hammer would probably work in a jiffy.
Seal installed:
Now flip the retaining cap over and lube up the new o-ring (from bag #4 or #5) and install. Note: Blister pack #4 and #5 contain 2 o-rings each (one large and one small) - you will not use the small one, just the large one!
Below is the axle bearing retaining shim (blister pack #1 in picture at beginning of document). Get one of these, grease it a little, and install into the retaining cap as indicated in the 2nd pic below.
The axle bearing retaining shim fits on the ledge right below the o-ring.
Now you can get ONE of the paper seals from bag #4 or #5 and place over the retaining cap (line up the recesses!). NOTE: There are 2 paper seals in each bag (#4 and #5) - You will only use 2 TOTAL (so you will have 2 left over after the conversion is complete).
Place the aluminum caliper bracket on. (put it on so that the flange and holes are towards the rear end of the car).
Then you can install the retaining cap on the axle. The two small recesses in the retaining cap go down (as shown in picture below). I used a little loctite on bearing cap screws, and then torqued them down.
Now take the original axle spacer (pic below) and clean it!
Lube the spacer, and then slide it over the stub shaft and "into" to the axle bearing retaining cap. NOTE: The beveled edge should go in first (to put it another way: the beveled edge should be pointing towards the engine). It may be a snug fit when it goes under the seal (if its too tight, loosen the axle bearing retaining cap screws a little to get it in, and then retighten).
It is now time for the hub! The hub simply slides over the stub axle.
Then you can take an axle spacer (from blister pack #2 picture at the beginning of this document) and slide it over the stub shaft also.
Then the castle-nut can go on:
Now you can use the angle iron tool, and torque the axle nut down to spec and put in a new cotter pin (from bag #4 or #5). I believe the Bentley manual calls for 243 ft. lbs., but in order to line up the cotter pin holes, you may need to go a little tighter (I did).
For the caliper installation, you may find it helpful to hand tighten a couple lug-nuts to keep the rotor from wobbling.
Before you install the calipers, you must install the brake pads. The first thing you need to do is open the calipers. The easiest way to do this is to push on the outside edges (near the rubber bellows).
Now you can pop in a brake pad. They will be a little spring loaded, so you have to push them down and in to get them to fit under the 'ledges' (you will see what I mean when you have the calipers and the pads in you hands).
Also: Its not a bad idea to put a little grease on the contact points of the brake pad (anywhere it touches the calipers) to keep the brakes from squealing. DO NOT put ANY grease on the friction side of the pads!!
Now you can insert the second brake pad, and slide the caliper closed (while pushing down on the second brake pad so that it will fit under the ledge).
When done, it should look something like this:
Now you can take the hardware from blister pack #3 (see picture at beginning of document) and mount the caliper. Make sure to use a washer and lockwasher on the backside. You may also need to use a spacer to center the rotor inside the gap in the calipers (see second pic below). A little loctite might not be a bad idea also.
Were almost there! All that's left is the brake lines, and e-brake cables.
I found that the very edge of the brass on the e-brake cable needs to be filed a bit to fit inside the tube on the car (yellow arrow). This end of the cable wont fit ALL the way inside the tube like the original cable, but it will be in enough to work.
When installing the e-brake cable, you can slowly feed the cable into the tube and grease it while you go.
The pics below show how I routed my e-brake cable:
The rubber portion of the e-brake cables are a tad too short, so its a tight fit. Note the zip-tie located near the rubber snubber to keep the line in the correct spot. After these pics were taken, I added some hose around the areas of the e-brake cable that were going to rub (to keep them from getting worn through).
The rear end of the e-brake cable simply slides into the big hole on the caliper. Then you can take the C-clip from blister pack #3 (see picture at beginning of document) and install it to keep this end of the cable from falling out.
You can see the C-clip better in this pic:
From this point I skipped to the hard brake lines (we will finish up the e-brake cables in a second). The hard brake lines need to be formed in order to fit around everything. You can do this with a special bending tool, or by hand (don't kink the line!). I did a little with a tool, and the rest by hand - you will notice my bends look like crap; this is because I ran the hard line about 3 different ways before I decided how I wanted it to run (so YOU guys don't have to guess at it like me!).
The following pictures should give you an idea how to run it:
Whatever you do, keep the hard lines on top of everything - DON'T run them underneath the calipers/rear diagonal arm (BAD idea!).
This bend help take up a little of the slack in the brake line that was left. Also notice the hose I zip-tied to the e-brake cable to keep it from getting a hole rubbed in it (it looks VERY close to the shock in this pic, but I assure you it isn't.)
Back to the e-brake cables: With the cables installed, you can run the nuts down on the e-brake cable inside the car about half-way:
Now at the back of the car, you have probably noticed that the actual cable itself is too long.
I haven't found a perfect fix for this YET, but so far the following worked for me: I went to the hardware store and bought an Aluminum ferrule set (below):
I took the round piece and used a dremel to cut out a slot in it.
Then I crimped it on the e-brake cable really tight (I used a BIG crimping tool). So far this has worked great for me.
Now you can put your wheels back on the car, lower it to the ground, and tighten the lugs. The next step is to bleed the brakes. Follow the Bentley/Haynes manuals procedures for this. Don't forget to put the e-brake boot back on.
One final word about the paint on the friction surfaces: When you first take your car for a test drive, don't expect the brakes to feel a lot different (or even any better) - Remember there is STILL paint on the friction surface. In-fact, you may hear it kinda grinding off as you apply the brakes. What you will want to do to get all the paint off is DRIVE the car. Go around the neighborhood 30 times and drag the brakes/pull the e-brake. It will start smelling like paint - but that's a good thing! The paint may also get a little gooey (making the brakes stick). Don't worry it will come off soon. Keep driving!!
With all the paint off, and the brakes "broken in" you should notice a difference in braking power (I can now lock up my 215's in the rear! - not that that's a good thing...). It takes me less effort to bring the car to a stop, and it stops a lot quicker. Its not as noticeable of a difference as the front disc brake conversion, but it IS noticeable. Overall its a great conversion. Should be nice in wet weather too!
UPDATE: After a couple weeks of driving with the new rear discs, I thought I would let everyone know how its going. The aluminum ferrule bit for the e-brake cables are still holding strong. One day the rear brakes squealed a bit, but now they make no noise. Also: A new noise started about 2 weeks after the install - it sounded like my CV's going out (click, click, click)... After pulling the wheels off, I checked the torque on the axle nuts and they were loose (even with the cotter pin in)!! My best guess is that everything settled in and loosened up a bit. I re-torqued, and added a new cotter-pin and so far the noise has not come back. My final suggestion is that anyone installing this kit may want to check their axle nut torques every week for a couple weeks after the install.
WARNING, use articles at own risk! Please, DO NOT blame me for anything wrong in the articles. I am not responsible for any damage to your vehicle, nor am I responsible for any bodily harm incurred as a result of using these articles. Use these articles as references only, ALWAYS try to be as safe as possible when working on your vehicle! Respect your car, and it will respect you!
