'65 GTV rear Dunlop brake 'calipers'

8333 Views 18 Replies 6 Participants Last post by Tom Frasca, Jan 17, 2017

Biba69

Discussion Starter · Mar 31, 2011

Does a great individual parts type diagram exist for these brakes?

Also, are (the equivalent of) rear wheel cylinder's rebuild kits available?

Biba

Reactions: 1

1 - 19 of 19 Posts

Stopwatch

· #2 · Mar 31, 2011

I couldn't find any rebuild kits for the Dunlop slave cylinders (Duetto) and new ones from one of the English suppliers were going to cost more than a complete upgrade to an LSD rear end and Ate brakes from a later spider.

The factory diagram only shows the slaves as a unit - no exploded diagram. Perhaps one of the experts will weigh in (Papajam?)

My car is a driver and the Dunlops were a liability. I can, however, understand the desire to retain the originality in a 100 point restoration.

Biba69

Discussion Starter · #3 · Apr 2, 2011

2

Stopwatch, thanks for replying. Is the 'wheel cylinder' with the pushrod on the lower right what you're talking about? I can't imagine there would be all that much difficulty having them rebuilt. Worst scenario the bores might have to be drilled/milled out and sleeved. The rubber boot might be a bit of a problem.

However, in the second photo, what is supposed to be accomplished with the gear on a movable arm. It can't turn so I'm befuddled by the arrangement. I gather it is for the hand brake.

Not really a concours concern, but Alfa's have always had good brakes, so I can't imagine if the Dunlops can be rebuilt, that they wouldn't work quite well. Quaint design in the rear, but it sure is easy to switch out the brake pads - assuming they're still available. The one's I removed looked almost new. I suspect the rear brakes were close to non operable.Try replacing the drum brake shoes in the rear of your 'new' ATE's. True, once done, they last a very long time.

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traga

· #4 · Apr 4, 2011

Biba,

I just finished a rebuild of my Dunlop rear calipers so I can comment on some of your questions. Try contacting Tony at AlfaStop in the UK for parts. He's done a great job of coming up with what I needed except for the rubber dust seal on the aluminum housing which goes over the rod. He has some rebuild kits for the cylinder but they may only be available for the later style. What you have pictured is the earlier type (I think). The ratchet mechanism in the aluminum housing is an automatic adjustment for the pads. If you press the ratchet back away from the threaded cylinder you should be able to turn the cylinder on the threaded rod. Others have complained about this mechanism being unreliable but mine seems to be working (on the bench so to speak) but I have not driven it yet.

Regards, Al
1967 Duetto in rehab

Biba69

Discussion Starter · #5 · Apr 4, 2011

Al, thanks for this knowledgeable information. Is the brake pad adjustment (theoretically) automatic, or does it need to be tweaked from time to time?

Some years ago Tony banned me from buying from AlfaStop apparently for my listing on the 750-101 group that the Spider wheel cylinders could be purchased from Moss Motors for much less than they are on his site.

I've managed without his 'services'.

There is a very good, not inexpensive, So.Cal. shop which can pretty much repair any wheel or MC cylinder. They sleeve with stainless when necessary.

Since nothing appeared to be broken inside the aluminum housing (do you agree?) I'll install as is (with fresh grease and buffed out housing)).

Biba

sprintgtc

· #6 · Apr 4, 2011

Biba, Try Chris at Highwoodalfa. He has new Dunlop rear wheel cylinders and they come with the rubber boot. They're about $100 each. Also, the Dunlops work great and are way cooler than the Ates. Just clean them up, adjust them properly, and off you go.

Biba69

Discussion Starter · #7 · Apr 5, 2011

Thanks Mike, I'm in good standing with Chris so I'll definitely get them from him. He also gets right back to me (and I assume everyone) with availability, costs, including shipping.

There are so many Alfa's in Seattle. Alfa's don't particularly like to be out in the rain (and snow), especially if they have to sleep outside. How does one keep the rust worms at bay 'up there'?

Andrew

· #8 · Apr 5, 2011

I rebuilt the wheel cylinders on my 65 TI, which worked fine and I should have left them alone, with kits from the UK, and both leaked slightly afterward.
I too would not go the fix-the-Dunlops route again except maybe on a GTA that required them for racing homologation, or a very original TI or Duetto that you didn't want to change axles on, and wanted to keep it original.
A friend now owns the car, and we're planning a 4.56 ATE axle swap pretty soon for the 5.12 Dunlop.
Andrew

Biba69

Discussion Starter · #9 · Apr 5, 2011

Mike, Andrew, does Chris sell complete push cylinders (thought I'd give that name a try) or is he only selling rebuild kits?

I dunno, the Dunlops are so eccentric that if they work reasonably decently, I'd like to stick with them. True, I've not run it by my client, but I'm sure he'll agree.

They're sort of like the Edward Scissorhands of disc brakes.

Andrew

· #10 · Apr 5, 2011

Eccentric is right. The problem mine had, beyond leaky new seals, was so much lost motion in the system that the pedal has to move a long way before the pushrod moves the pads far enough to press the disks. And the pads are adjusted right.
I bought seal kits from AlfaStop. I don't think he had new cylinders, but I'm not certain. He had new pistons for the front disks, which I did new, and they were incredible things.
Andrew

sprintgtc

· #11 · Apr 5, 2011

Biba, the ones Chris sells are new and have an aluminum body. My Super's original ones were steel. I have seen slop issues if the clevis pins are worn or the clevis holes have elongated, but if the caliper is in good shape, the pedal feel is great. I had no issues with a low pedal in my Super. (I've since sold the car).

And yes, we are wet up here in Seattle, but traditionally salt free in the winter. I say traditionally because this year the city decided to dump huge mounds of salt on the surface streets to treat the 1/2 inch of snow we receive annually. There is an upside to the lack of sun: my cars all have perfect, uncracked dashes.

traga

· #12 · Apr 7, 2011

Biba,
On the adjustment mechanism, my experience is limited but. But the adjustment worked on the car after putting the pads in. When the emergency brake cable was pulled the mechanism did adjust as expected to tighten things up nicely. I expect if things are too worn (both the ratchet and linkage pins/holes) then things may not work. There is also a small spring clip at the base of the threaded aluminum ratchet cylinder that puts a drag on it so it does not back rotate when the ratchet paw retracts. See photo for the spring clip. Had a scare after breaking one of them but was happy to find that a new one was available. So in theory and in limited practice the adjustment mechanism works.

Good luck.

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Biba69

Discussion Starter · #13 · Apr 7, 2011

Al (traga), why is your number of posts stuck on 51? In any event I appreciate your comments, along with the heads-up regarding the spring clip. Who carries them and do they also have the boots/dust covers?

Also, any trick to removing the ratchet itself?

I found no broken bits inside the case, but the ratchet/rod just flop around so the clip ends must be broken off.

Biba

traga

· #14 · Apr 8, 2011

Biba,

I don’t think the flopping around is cause for concern. The spring clip does not secure things per say, only acts to put resistance on rotation of the aluminum cylinder. If the rod is removed (unscrew it) then the aluminum cylinder with spring clip should come out. It’s a bit tricky to get it past the ratchet; the ratchet may need to be pushed back. When putting things back together care is needed to make sure the spring clip is seated on the pivot piece. Things will make sense I think when you get a look at things disassembled. Don’t think the clip is prone to breaking. Mine was fine until I found it under my foot in pieces. The replacement piece was supplied by your acquaintance at AlfaStop. The boots were not available however, so one must come up with something clever. Not that I recommend it but I used some thin leather dried over a mandrel to make a boot and then coated it with plasti-dip. I then secured it in the groove with a wrap of wire. I take it that the photo you posted was after you cleaned things up. There should be a good amount of grease in there (lithium grease or such).

Happy Roads, Al

BTW – Strange about the 51 post thing. No clue……

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Biba69

Discussion Starter · #15 · Apr 8, 2011

Al, thanks. I'll be getting some items from Chris at Highwood fairly soon, so will have him get the clips (if needed) from AlfaStop. I'm pretty sure they buy from one another on occasion.

For now I've put the cleanish caliper away, but still have the disassembled right one to scrape off and clean. I'm a bit confused, if I unscrew the rod from the ratchet, why would the ratchet be in the way or are you referring to the 'other' ratchet/gear part?

Hey, you're up to 52 posts.

traga

· #16 · Apr 9, 2011

Biba,

I'm motivated to answer your question to see if I can get my post number up to 53

. I've been know to confuse things when giving explanations. I'll see if I can confuse them more.... Referencing the attached diagram it looks like a ratchet is made up of a gear and a pawl. So the rod would be removed from the gear (threaded aluminum cylinder with spring clip at base). It would then be loose and can be removed but needs to get past the pawl (spring loaded mechanism). Clear as mud????? I guess I need to add that the spring clip was considered a very rare old stock item and it was priced accordingly.

Regards, Al

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Biba69

Discussion Starter · #17 · Apr 9, 2011

Al, what a nice drawing. Thank you. It sounds as if I should check out the clips on these units to see if I need to get them. If NOS and not reproductions, there is obviously a limited supply.

I see that this is now your second 53rd post.

Tom Frasca

· #18 · Jan 17, 2017

Dunlop Diagrams

Biba69 said:
Does a great individual parts type diagram exist for these brakes?

Also, are (the equivalent of) rear wheel cylinder's rebuild kits available?

Biba

:grin2:

Series 11 , 111 front and MK1 attached PDF hope this helps..

Tom Frasca

· #19 · Jan 17, 2017 (Edited)

Dunlop Diagrams

Not sure if I did this right or not let me know, attached in PDF file are 4 illustrations of exploded views...let me know if this helps.

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