Rear Disk Brake Conversion Experience

This document describes the process I used to convert the rear brakes of my Volkswagen GTi from drums to disks.

This isn't intended to be an official or approved procedure for this conversion, it just worked for me. Before starting my project I did an extensive search of the Internet and could never find any instructions to help me out.  I thought I'd share my experience so others do not have the same difficulty.

After completing the conversion, I offered these instructions to be posted on Jan Vandenbrande's web site.  Jan informed me that European Car magazine did an article on this a while back.  I haven't had the opportunity to see this article, but it may be worth finding if you are going to try a conversion yourself.  I did the conversion "by the seat of my pants" as they say, using the Bentley manual for reference. 

Background 
My car was born a 1992 GTi 8 valve, which like many other VWs came standard with rear drum brakes.   Unhappy with the performance of this setup and faced with the expense of replacing my drum brake pads and resurfacing my drums to get rid of an annoying squeak, I decided to convert the rear braking setup to disk brakes.  This document will describe the tools, parts and process I used to complete this conversion.

Difficulty
On a scale of 1 to 10, where 1 is changing your oil and 10 is doing an engine conversion, this procedure rates around a 6.  The job can be completed in a day (barring mishaps) with standard hand tools.

The job is not mechanically difficult, but it involves changing components in one of the primary safety systems in the vehicle.  I did this conversion with that understanding and complete faith in my mechanical abilities.  Others should consider their level of comfort and experience, and defer work of this sort to professionals if not completely confident.  Bentley has some good verbiage that says a similar thing, basically what I'm trying to say is:  DON'T MESS WITH YOUR BRAKES UNLESS YOU ARE CERTAIN ABOUT WHAT YOU ARE DOING AND WILLING TO ACCEPT ANY CONSEQUENCES.

Cost
I chose to swap only the rear braking components, rather than the whole rear axle beam.  I was also able to preserve my stock master cylinder and rear proportioning valve, which saved me a considerable amount of time and money.

The parts alone add up to well over $1000 if purchased new from your a VW dealer parts department.  Many of the OE parts are available aftermarket from VW performance shops for considerably less money.

Some tuners offer all of the parts necessary for this conversion as a kit.  I chose not to go this route, thinking that I could do the conversion much less expensively buying components individually.

The other route to save money is to purchase used parts.  I started this project expecting to get all parts other than wear items (brake pads, rotors, etc.) from a local salvage yard.  I quickly found that the used parts I had access to weren't in good enough condition for my needs.  I wasn't willing to compromise the safety of my brakes, so I ended up purchasing most of the parts new.  (I did buy salvaged stub axles.)

Parts
The parts I used are listed below.  Keep in mind, these were the parts necessary to convert my '92 GTi to rear disk brakes and the parts required to convert other vehicles may vary.

4	Caliper Carrier Bolts
2	Grease Seals
2	Outer Bearing Caps
2	Metal Bearing Covers
2	Brake Line Holder Clips
6	Brake Line Holders
8	Bolts - for Stub Axles
2	Solid Brake Lines -- (20" pre bent or custom bend)
1	Caliper (Slide) Rebuild Kit
2	Rotors (4 / 100 bolt pattern for 16v GTi)
1 set	Brake Pads
2	Rear Wheel Bearings - Inner	
2	Rear Wheel Bearings - Outer
2	Rear Calipers
2	Backing Plates
2	Stub Axles
2	Caliper Carriers
1 set	Flexible Brake Lines (six line set for 16v GTi)
2 	E-Brake Cables (for 16v GTi)
2	Steel cotter pins
2	Axle Nuts
2 	Crowned retaining cover/Castellated nut retainer (goes over axle nut to hold it in place)
2	Thrust Washers
2 	E-Brake Sheaths

Tool list
Torque Wrench
Ratchets
Breaker bar
Metric Sockets (The usual sizes plus a big one for the axle bolt - 30mm I think)
Metric Hex/Allen head Socket (8mm for caliper carrier bolts)
Metric Wrenches

I also had to use:
10mm x 1.50 tap
Angle Grinder
Power Drill
Hardened Steel Drill Bits
(keep reading, you'll see why)

Supplies list
Thread locking compound
Hi-temp disk brake bearing grease
Brake fluid
Caliper slide lubricant

Before tearing car apart
1.  Buy all parts.
2.  Press bearing races into hubs.
3.  Install the caliper slides into the caliper carriers.
	- Lubricate the caliper slides with the hi-temp lubricant and install with the little rubber boots.
4.  Think through the process and read everything you can get your hands on.

Remove all parts not necessary
1.  Park car on a flat work surface, chock front wheels.
2.  Loosen rear lug nuts.
3.  Jack up rear of car.
4.  Put jack stands under rear of the car.
5.  Remove rear wheel lug bolts.
6.  Remove rear wheels.
7.  From inside car, release tension from the emergency brake by moving the handle downward.
8.  For each rear wheel:
	- Remove grease cap.
	- Remove and discard cotter pin.
	- Remove crowned retaining cover over axle nut.
	- Remove big nut on end of stub axle.
	- Remove thrust washer.
	- Remove brake drum and outer bearing:
		- Rotate drum until one of the lug holes is at approximately the 10 o'clock position.
		- Use a flat bladed screwdriver to pry up the adjusting wedge through the lug hole.
		- Remove brake drum and outer bearing.
		- Remove drum brake pads:
			- Remove pad retaining pins.
			- Hold back of retaining pins and use a set of pliers to compress spring and rotate retaining collar 90 degrees until it comes off. 
			- Remove retainers and springs.
			- Remove pins.
			- Remove horizontal spring at bottom of pads (tricky -- there's probably a special tool).
			- Unhook e-brake cable.
			- Remove pads.
	- Unscrew the solid brake line from piston at top back of brake backing plate.
	- Remove four 17mm blots holding backing plate and stub axle to axle beam.**
	- Remove backing plate.
	- Remove stub axle (and plastic spacer).
	- Unscrew the other end of solid brake line from junction at front of rear axle beam.
	- Remove the solid brake line.
	- Remove the flexible brake line that goes from the solid line coming out of proportioning valve to the junction at front of rear axle beam.
	- Remove emergency brake cables from under center of car.
		- From inside the car remove the emergency brake cover.
		- Using two 10 mm wrenches, loosen the lock nut at the end of the cable.
		- Remove the lock nut and the adjusting nut from the end of the cable.
		- From underneath the rear of the car, pull each of the e-brake cables out individually.
		- Take care to leave metal sleeves that route the cables to the e-brake handle in car body.

** If you're lucky like I am, you will twist off the tops of several of the bolts that hold the backing plates to the stub axles in the process of trying to remove the bolts.  This is where the angle grinder, drill and 10 mm tap came in handy ;-)

Install the new parts.
1.  Lubricate and insert new emergency brake cables into sleeves underneath the center of the car.
2.  From inside car, replace nuts on the end of the e-brake cable to hold it in place.  
	- Do not tighten yet.  The other end must be attached to the caliper first.
3.  Remove and replace flexible brake line that goes from the solid line coming out of proportioning valve to the junction at front of rear axle beam.
	- Use the spring clips between all brake line connections.
4.  Bend solid brake line that runs from the flexible brake at the junction at front of rear axle beam line to the final flexible brake line that goes to caliper at the rear of the axle beam.
	- Follow the contours of the rear axle beam.
	- Use brake line bending tools to avoid crushing the line while bending it.
	- Do not attach the rearmost flexible brake line yet.
5.  Install brake line retaining clip at back of rear beam.  
	- Mine was oriented with the end with brake line hole pointed up.
	-  There is a production date that decides which calipers to use and which way this part sits.
		-  I think it is sometime in 1988 ???
6.  Place stub axle against the axle beam, the bolt holes only allow one alignment.
	- Position with caliper carrier mounting holes at 1 o'clock and 3 o'clock - toward rear of car.
7.  Place the backing plate over the stub axle:
	-  Align the backing plate with the bolt holes, they only fit one way.
	-  The backing plates curve away toward the center of the car.
	-  This was different than the picture in both Bentley and Chilton manuals.
8.  Insert stub axle mounting bolts with washers through mounting holes in backing plate and stub axle:
	-  Use a thread locking compound. 
	-  Torque to specification.
9.  Install metal bearing cup, curved outward, onto stub axle.  
	-  Using a soft faced mallet and a suitable drift, knock into position over stub axle.
10. Pack inner bearings with grease.
11. Put inner bearing in race and press in the bearing grease seal (before putting on car).
12. Grease inside of hub assembly between bearings.
13. Pack outer bearings with grease.
14. Grease stub axle.
15. Install rotor/hub assembly on stub axle.
16. Insert outer bearing.
17. Insert thrust washer over bearing.
	- Be sure to line up the tab on the inside with the slot in the axle.
18. Install retaining nut on stub axle.
19. Adjust for free play.
	- Do not overtorque.  Refer to your manual for instructions on tightening this nut.
20. Install special crowned retaining cover such that the cotter pin can be inserted into the stub axle.
21. Insert cotter pin from top and bend ends upward from the bottom.
22. Fill grease cap with grease, install in hub with a soft faced mallet.
	- Do not deform grease cap.
23. Bolt the caliper carrier to the stub axle.  Torque bolts to specification.
24. Install the flexible brake line into the caliper and tighten.  Torque to specification.
25. Insert flexible brake line into solid brake line and tighten.  Torque to specification.
26. Install brake pads.
27. Push caliper piston into the caliper before installing caliper over pads.
	- This may require 12 mm allen wrench or special tool depending on the piston type.
	- I think there is a FAQ on this subject.
28. Install caliper onto caliper slides in the caliper carrier.
	- Torque mounting bolts to specification, holding slides from turning with a helper wrench.
29. Insert ends of emergency brake cable through guide holes and into attachment point on caliper.
	- Be sure not to damage the rubber boot on the end of the emergency brake line.
30. Put road wheel on car.
31. Install lug bolts.  Tighten.

After finishing both sides
1.  Tighten emergency brake cables inside car.  See a manual for proper adjustment procedure.
2.  Remove jack stands.
3.  Let car down.
4.  Torque wheel bolts to specification.
(If you feel like it, now is a good time to install the front flexible brake lines that came with the set.)
5.  Flush front and rear brake lines and bleed out all bubbles taking care to never let the reservoir dry up.
6.  Test emergency brake.
7.  Test brakes in driveway.
8.  Test brakes on road.
9.  Break in the new brake pads.

Results
I've had this setup for about two months now, it seems to be working well.  There is a noticeable difference in stopping power and pedal feel.  However, the pedal feel may be attributed to the stainless steel lines that I installed at the same time.  The primary result is that I feel more confident in the braking power of my vehicle.

Charlie Sprigg
'92 GTi G60
10/30/98