Rear brakes.

[Lee]

Okay. I will try to develop the subject of rear disc brakes for 02s by trying to be as general as possible and not specific to a brand or supplier.

First, on top of the wow factor, what do you gain by installing rear disc brakes? Let's say that from the 2002 rear drums, you already upgraded to the bigger 320 drums and found that you may have gained a bit of braking power, but still had to continuously adjust the eccentrics and realized that they overheat pretty fast when driving hard on a track. What can you do then to solve that problem, while gaining a bit more of pedal modulation?

The solution adopted by most people for the past 15 years has been to use different parts from different cars and assemble a rear kit. Mainly, it consists of front VW Rabbit rotors (solid and about 9.5" in diameter) and rear calipers with integral parking/emergency brakes from the GTI or Jetta. This solution requires to have the hubs machined so that their outer diameters tightly fits the inside diameter of the rotor. This is what will center the rotor on the hub. I have no experience with other brands of rotors from the set I first bought, I cannot judge if there is a discrepency between rotors. Hopefully it is not required to machine a new set of hubs everytime rotors are changed.

The caliper is positionned almost horizontally under the rotor as there is just no room to have it in the usual vertical position, like most rear calipers. That is due to the lower shock bracket that interferes. An adapter is required to mount the caliper carrier to the trailing arm. The adapter cannot be made from 1/2" aluminum stock as it is a tiny bit too thick. You can use 1/4" steel and a few washers in between the caliper and the adapter. It will be a real PITA to install the washers. The main (and perhaps only) benefit of this whole configuration is the handbrake which connects directly. But each time you want to bleed the rear calipers, then you must unhook the brake cable, unbolt the caliper from the adapter, bleed the brakes, and bolt them back. Not fun at the track.

Some shops have made new developments around this basic set-up and solved several problems inherent to the configuration. I have heard that Ireland Engineering has a new kit where rotors are vented and calipers have a nipple located upward, allowing to leave the caliper in position when bleeding them. I believe that the new and old set-up are perfect for a street driven 2002, and occasionaly track driven car, and that mostly everyone will be satisfied. But it will show its limitations when it comes to endurance to overheat. The vented kit will nonetheless be superior to the solid one. The problem remains the sliding caliper which doesn't have the stifness of a fixed caliper. In term of hydraulic power, the rear VW kits are the perfect match to a front Superite caliper with 1.75" pistons on 11.75" rotors. Believe me, it is a fun combo that yelds a much better pedal modulation and braking precision and strength than the old drum stuff. I feel that a rear VW kit with front Tii/e12/e24 calipers on e21 vented rotors might have too much rear bias when driven hard. So, a bias valve must be used.

I would be glad to hear from other developments on rear disc brakes. On the next installment, I will entertain you on Massive's new rear kit which has been a 3 month development (plus idle moments, waiting for parts to be machined). Kit is finally done, produced, anodized/plated and shipping will start the first week of April after weeks (if not months) of waiting - End of the infomercial.

[Todd21]

Lee,

I sent you an email. Please respond so I can attach additional info.

Thanks,

Todd

[Lee]

Hi Todd

Everyone is free to contribute. So, just insert your own post in the discussion. It would be fun to have different points of view. Some may say that rear discs are not needed, while some say not to drive hard without them. There have been half a dozen solutions offered to owners and everyone sems to have addressed a particular solution.

[Todd21]

Summary:

This write up outlines the conversion of the rear brakes from drums to disks using VW parts. This write up places the calipers in a typical 3 or 9 o’clock position. This write up does require removing the original stock mount from the trialing arm. The write up is for non-vented disks and calipers and can be configured to use the existing parking brake.

All parts for this conversion were either reused from a yard or fabricated. The fabricated parts are made of carbon steel A36 plate 3/8” thick, or 1” carbon steel (1040) rod.

This write up uses the stock master cylinder with the addition of a proportional valve to reduce the pressure set to the rear brakes.

Donor car info:

· Rabbit Mk1 (A1/Typ 17, 1974-1984)

· Golf Mk2 (A2/Typ 19E, 1985-1992)

· Golf Mk4 (A4/Typ 1J, 1998-Present)

Parts needed:

QTY Description

2) VW Calipers from MK4, 2000 to 2006 Golf, Beetle, or Jetta (with lines)

2) VW Carrier Brackets from MK2, 1985 to 1989 Golf or Jetta

2) VW Rotors from MK1 (74-84 Rabbit) (239x12mm)

2) Reduced OD hubs from 2002 (existing hubs can be modified)

2) Adapter plates (see drawing)

6) M10x25 Socket Head Cap Screw

2) M10x20 Flat Head Cap Screw

1) Proportioning valve for rear brakes

1) 3’ section of 3/16” steel brake line

Procedure:

Start by jacking the rear of the car and placing jack stands under it to allow for safe work. This should be done on a flat hard surface it at all possible. All typical safety precautions should be taken to prevent the car from falling during the conversion. Very little, if any work will require getting under the car, but always err on the safe side. While we love our cars they can be replaced, we cannot.

Remove the rear wheels, brake drums, and hubs exposing the brake shoe assembly. The components of the rear drum brake assembly will be completely removed, including the backing plate attached to the spindle tube flange. The cable for the parking brake can be left hanging loose. The hard brake line can be removed back to the connection with the flex line at the trailing arm.

Remove the shock absorber mounting nut and slide the shock absorber off the trailing arm mount. Using a grinder or port-a-band saw cut the shock absorber mount off the flange. This is required to allow clearance for the caliper piston. The flange can be relieved as required during final fit to minimize the amount of the flange removed.

Install the fabricated adapter plates (see drawing) to the spindle tube flange using two socket head cap screws (SHCS) in the front holes and two flat head socket cap screws (FHCS) in the rear holes. The FHCS are required to allow clearance for the carrier bracket. Loc-tite 242 (blue) should be applied to all fasteners.

The rear hubs will be reduced on the outside diameter to allow the brake disk to pass over it. Take a measurement of the inside diameter of the brake disk “top hat” and then turn down the outside of the hub to allow the two parts to mate. Once the hub and disk is installed, test fit the carrier bracket and caliper to insure proper fit. The carrier bracket may require the slot for the disk to be opened depending on the location of the disk and hub.

Once the hub and disk are installed and the carrier bracket and caliper are installed, the brake line from the VW can be installed on the trialing arm. Straighten out the hard line to allow for it to be routed along the trailing arm similar to the original line. Attach the hard line end to the fitting on the trailing arm and then route the flex end to the caliper. The banjo mount on the caliper may require turning 90 degrees to create clearance with the inside of the rear wheels.

Install the shock to the new mounting location.

Install the proportional valve in the line to the rear brake calipers.

Bleed the system down. This will take some time since the system has been broken into in more than one location.

The parking brake cables can be attached to the calipers by extending the cable using a locking chain link or other means. The cables are not long enough to make the connection as is so I used a small chain link that I got a home depot to extend it. While it is not perfect, it does work very well.

Install the rear wheels and adjust the proportioning valve to achieve proper bias.

There are other ways to do this conversion and I have used the work of others to guide my attempt.

[Lee]

Nice. Pretty inventive solution. I never tought of moving the lower shock pick-up point. That's called thinking outside of the box...

[instructorbill]

(nt)

[Guest Anonymous]

Todd looking at an older writeup on rear brakes, really like what you did but cant figure out how you mounted the rear shock absorber, I saw hole at the top of the bracket, but cant seem to figure out how it mounts, do you have any closeup pictures thanks

[Lee]

If you are talking about the lower suspension mount, then you must probably weld a correctly oriented bung into the hole.

[Todd21]

Lee is correct kind of.....

I actually turned out a boss for the shock mounting bolt. I counterbored the boss for the head of the bolt. Inserted the bolt and welded it in so it couldn't turn as I tightened the nut.

Then.... here's the tricky part, I ground the boss to a 21 degree angle on the bolt head end. My best attempt and getting measurements on the boss orientation put it at 21 degrees down from the horizontal and rotated around 11 degrees to get the proper position. Just put the bolt/boss in the bottom mount of the shock and take a look. If it doesn't look right grind the angle to suit you and then put in back in the shock and see if it looks correct.

Tacked it into place and then removed the plate and fully welded. The position on the drawing is for reference.

The reason for moving the shock boss was the caliper being in the same location as the stock shock boss. The fact that the boss moved the mount further inboard actually kept the geomerty somewhat correct. This does collapse the shock more than normal but with the wheel and spring removed I checked the shock travel and there is no way the shock would bottom out before the wheel and tire would strike the fender well.

[Todd21]

Todd looking at an older writeup on rear brakes, really like what you did but cant figure out how you mounted the rear shock absorber, I saw hole at the top of the bracket, but cant seem to figure out how it mounts, do you have any closeup pictures thanks

If you go back up to the third picture from the top you will see the boss I built to relocate the shock mount. In the photo it hasn't been located and tacked into place yet. Good luck with your build and if I can be of any assistance just let me know.

Todd

[oz02]

Great write up Todd21.

Wondering if you could add some more dimensions to the drawing. I'd like to know some measurements to locate the mounting holes for the calipers - there is only the distance from each other, i realise they would be centred around the main hole, but how far offset?

Also could you add some dimensions on the relocated shock mounting position? I'm thinking i'll make up a square plate and mount the calipers upside down, but others might like that info.

Great post, thanks,

[Todd21]

Wondering if you could add some more dimensions to the drawing. I'd like to know some measurements to locate the mounting holes for the calipers - there is only the distance from each other, i realise they would be centred around the main hole, but how far offset?

Also could you add some dimensions on the relocated shock mounting position? I'm thinking i'll make up a square plate and mount the calipers upside down, but others might like that info.

Great post, thanks,

Hey there,

Sorry for the omission, that diamension is 48mm for the horizontal offset location of the caliper bracket holes. They are centered vertically on the large hole.

The shock boss location is not as critical because you can tack it in place and then go back and fully weld. The location is 82mm vertical and 48mm horizontal from center of large hole. My drawing shows a 26mm circle to indicate the position because I used 1" (25.4mm) steel rod to build the boss. That left plenty of material around the edge to weld the boss and the plate together.

As for the eBrake cable I used some small links I got at the hardware store to extend the stock cables with no other modification to the existing eBrake cable bracket already on the caliper.

Todd

[miilor]

what is the measurement?

[Todd21]

48mm

[miilor]

ok, gracias