308 rear brakes

Can someone explain to me how the rear brakes work when the pucks are secured by the adjuster screws.
As the pads wear how do the pucks move out of the caliper?
Thanks
Bill

 

The rear main brakes are self-adjusting pistons just like all hydraulic disk brakes.

The handbrake mechanism is a rather Walt Disneyesque contraption that employs those setscrews. They essentially limit the piston's ability to retract when the cable-operated lever is actuated.

 

LOL .. interesting isnt it !

I have totally stripped , re-kitted and reassembled my rear calipers.

If you dissassemble everything and install the screw into the piston it may at first seem very well secured.
Now GENTLY hold the screw and twist it side to side a little , , you will find that the female thread assembly inside the piston can move around. It is spring loaded or appears to be.

As best I understand it the piston will actually rotate and screw itself out on the male thread as the brake pads wear. Keep in mind the pads normally wear very slowly.

I was tempted to place a mark on the piston relative to something to check this hypothesis ( I'm not a million percent certain ) .....the trouble is what would I mark it with and I would have to pull the whole damn thing apart to see if the piston had rotated.

All I do know is the brakes have been installed for thousands of kilometers , they work fine , , the pads have worn a bit and there is no more than a normal (few thousandths of an inch) gap between the pads and discs.

The same calpiers were fitted to Ford Fairlanes (so I am assured by a large brake/clutch repairers) here in Australia for 1 year only ........ Ford wised up and lost them real quick.

 

It would be great if you can find out what Ford replaced them with, as hopefully they could be installed on the 308 too!

They may have been effective on a light car like the Porsche 914, but this set-up (inboard pads only for the handbrake), just isn't powerful for a heavier car like the 308.

It'd be a different story altogether if the caliper body would slide (thus putting the outboard pad to use), then it would be an effective parking/handbrake.

 

Rear brake internal components:
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thank you very much fo those pics, Peter !


I did a complete overhaul on the rear brake calipers on my car 4 years ago
but couldn`t take pics at that time

 

Peter,

Thanks,, have those on my 1981 Euro Mondial-8....
ATE steel Calipers,,

on some Porsche models,, "S" I believe, the Front ATE brakes have aluminum calipers.
Much lighter...!
I'm looking for a set.

Edwardo

 

Don't all of the Mondials use sliding calipers? I have a Ferrari North America-issued service/introductory manual for the 1982 Mondial 8 and it shows a break-down of the calipers and they're sliding (they call "floating") calipers... The rear parking brake is separate from the caliper, as it is a drum type contained in the brake disc bell. I wonder if the very first cars just carried-over GT4 components?

 

I did mine last year and I knew I had no choice in taking photos - they looked to be too complicated to try and just remember how it all went together! I even took notes too!

In addition to the rebuild I also restored them, replating the components:
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Extremely good point , , I shall try to find out which model Fairlane used the ATE's , , , , the guys at the brake and clutch place all looked at one another and smirked / laughed when I put the ATE on their bench ( I was looking for EPDM o-rings at the time ).

These horrble calipers have a reputation so it seems.

The Australian Fairlane was a big heavy car just like its earlier American cousins.

The "floating calpier" is also called a "self centring capliper" in some circles , , its disadvantage is there is only 1 piston to push with. I think brake feel and effectiveness may be affected (negatively) if an opposed piston set up was substituted with a self centring type. That would be because the master cylinder to brake piston ratio would change.
I'd like to know what other think ...

 

I remember thinking " how heavy do they wanna make these damn things ? " ....... a set of aluminium calipers would reduce unsprung weight enormously and probably even pass a concours without being noticed .......... keep us informed if anything comes up please !

 

The way I look at it, if brake-swept-area is somewhat equal and if the piston volume is similar, I think there shouldn't be any major problems/differences in application.

I don't remember the specific thread name, but there was talk here of installing Audi A4 brakes on 308's?...

 

A lot of myths on how the internal adjustment mechanism works on these. Pistons do not turn on the shafts and self adjust.

To the original question: The internal adjustment mechanism allows the pistons to move on the adjusters roughly 1/8".

The key to having great brakes is to perform a venting clearance adjustment annually. This allows the handbrake to work properly (Only the inside piston is actuated in handbrake operation. If the venting clearance is set properly it will force the rotor over against the outside pad for effective operation). These should be set at .004" to .008 on the high-side of the rotor runout.

I've yet to find a lighter bolt on solution with a handbrake.

Regarding ATE S-Calipers (911S, 911RS and first year 930 Turbo - 1969 through 1976). Those are fairly common and should bolt on early 308's with the 20mm rotors. They will save you almost 8lbs of unsprung weight up front. The A-Caliper on your car weights 9lbs. 2oz. (without pads, pins and springs). The S-Caliper weighs 5lbs. 6oz.

I have two non-customer pairs in inventory now being restored. They'll be ready next month.

 

Eric,
Thanks for clearing up the mystery. If the lightweight Porsche units really fit my 308 and they don't break my f-car piggy bank put me in line for a set.
Thanks
Bill

 

Yes, but at least actuation will be more effective with a sliding/floating caliper, as with the current fixed set-up, it takes considerable force to deflect the disc so as to engage that other pad.

I've tried to look up diagrams/images of that Australian Ford Fairlane brakes but couldn't come up with much. PBR Brakes lists replacement calipers for modern Fairlanes but hardly any for '70's versions (it seems Holden Torana's used the same brakes too?). Any other models might use them?...

 

Peter,
Great work! How did you keep from plating the piston bores?

Rick

 

Not really. That's what they're designed to do. It's fairly easy to deflect a rotor .004 - .008 against a pad with just your hand. As long as the venting clearance is set up properly it's rock solid.

Great job on your rebuild BTW.

 

GM tried both designs, my 1967 Pontiac Firebird came with 4 piston front disc calipers originally....

At some point a sharp guy at Brake Check pointed out that if I went with a newer spindle off another model (it was the mid 70's at this point) the current GM caliper could be fitted which indeed only had one large piston clamping down on the rotor.

Easier to keep the piston sealed properly vs. the 4 piston calipers.

 

Peter,

I wish I had floaters,,, but, I would also have to change the Euro Hand-brake mount.
(Yes, ATEs,,, I have,,, my Mondial 8, is a 1981 Euro,,, and, this IS the Euro set-up per the Mondial 8, Mondial QV workshop manual. CAT. N. 281/83) Bummer.

But, if I find an Aluminum set.


Edwardo

 

Hint for getting the rear emergency brake "Return Spring" in place. I was grabbing it with a pair of pliers cushioned with a piece of cardboard trying not to strip off all my brand new zinc plating. Here is what I came up with. In the USA, 1/2" copper pipe will just slide over the post for the spring end. Come back from the end about 1/8" on the pipe (just enough to drill a 1/8" hole) on opposite edges of the pipe. Use a file or a dremel and open up the holes to create a slot. Grab that spring in the slot and wind it about 1/4 turn until the spring lines up with the slot. Push down and the pipe slides over the emergency brake lever and the spring slides right into place Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login . Afterwards, it took a few taps with a persuader (hammer) to seat it down another bit to get it back in position. Worked great, and I had the scrap lying around.

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