FAQ
Project.

Rebuilding Rear Brakes
By
Sam Doh
eMmail: sonoramicommando@yahoo.com

Introduction

There is really not much to working on twin-cam era Fiat brakes. It works well, easy to maintain and service. Having said that, a tip or two always come in handy, especially dealing with something like this, which you are not likely to do too often.

It all started when I had the car up on jack stands for shocks and springs replacement and waiting for the parts to arrive. I figured I'll do something about the rear brakes while the cars up - the pads were worn down real bad. It didn't seem to being seeing much action there with cobwebs in there and sure enough, when it came to screwing in the pistons to give the new pads to be fitted, it wouldn't budge. I could've put the old pads back and forgotten all about it (only for a while though) but that didn't work out either because I tried to unscrew it to see if it was reverse threaded - it wasn't and the piston came out further enough to prevent re-use of the old pads. Those brake cleaning spray didn't do any good either. So, there was no other option but to take them off the car and overhaul.

Disassembly

First up, gotta have the right tools.
From left top, clockwise, a circlip plier (internal), a vicegrip, a hammer, a flat file (or a fat, flat blade screwdriver, if not available), a cresent (or correct size wrenches), G clamp (This one is modified slightly for the application), a drift and a punch.

A dirty calipers, ready to be disassembled.

bdis

A flat file is fit in the slot of the piston face and turned counter clockwise to loosen it. At first, it would be best
to get started with the side of the file in the slot as shown in the picture as the piston would be rather reluctant to move.

Once you break free the piston using a file, it should be relatively straightforward to unscrew until the piston is off the threaded rod. If it doesn’t drop out, use a vice grip to grab it around the piston (make sure grab it by the smaller diameter of the piston) and wiggle it out turning it back and forth. You could give it a little more encouragement with a hammer as shown, if necessary.

pisremove

Here is a photo of the calipers with the piston removed.

pisrem

This is the part where the job gets slightly tricky. An extra pair of hands comes in handy, especially the first time around, but not necessary.

mech1

First, pull back the rubber boot to expose the mechanism – it cannot be removed just yet.

Use circlip pliers to removed the circlip.

Now one can use one of two methods to get the pin and the rest of the bits out.

1. Use a plain old drift/punch to drive out the pin. It takes a bit of force to push it out because the pin is being
pushed normal to the pin axis due to spring washers in compression.

2. Use a G-clamp to clamp up the threaded rod at the pin end (on which piston was screwed) against the calipers body to relieve spring washer compression. It can be a bit tricky if the head of the G-clamp is too big to fit in there. We had this problem but got around it by grinding little notches to fit. This is definitely easier way of getting the pin out. Besides, you have to use this method to put things back together later on.
handbrake

With the handbrake mechanism is out, the rubber boot can come off.
handbrake2

Push out the threaded rod. Make note of the way the spring washers are stacked or compression will be all wrong when put together. Manuals (Autobooks, Intereurope and Fiat Factory shop manual) give excellent sectional view of this.

PinRemove

Disassembly is complete.

Assembly

After thoroughly cleaning the disassembled parts with solvent and a brush (parts washing bath works great), we can get started on assembly.

asembly1

Be sure to stack the spring washers in correct orientation. (Refer to a manual or a sketch if one was made during disassembly)

Put a shaft seal in the groove.

insertion

Insert the pin into the calipers housing.
Handbrake

Assembly of the hand brake parts is reverse of disassembly. Install the rubber boot in the pin. Apply grease (wheel bearing grease or similar heavy grease works fine) over the washers and the area which is to be covered by the rubber boot. The grease, in my view, is more for preventing moisture and dirt ingress that lubricating as the movement in there is minimal.

Compress the spring washers with a G-clamp over the threaded rod and the calipers housing. Insert the wedge shaped bit and hold while pushing in the pin.

Replace the circlips.

Rubber Boot

More grease to seal the deal and cover it up with the rubber boot.

Finished Caliper

Put seals in the piston bore and over the piston. Lubricate the seal surfaces with brake fluid and screw in the piston.

It's all done.