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Discussion Starter #1
I'm putting the original rear end/brake setup back in my Duetto after running an ATE setup since buying the car.

My question is whether the fingers are meant to be bent to exert no load (or a slight retraction pressure) on the pads when the brakes are assembled and not activated? I'm guessing the fingers on the caliper serve as pad retractors??? My problem is that the new pads are much thicker than the pads removed and the fingers are acting to compress the pads to the point that the rotor doesn't come close to fitting between them.

I'm bench assembling the mechanical components- no wheel cylinder, springs, etc are yet attached.

Thanks for any help or links to rebuild manuals.
 

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I am in the process of putting mew pads and rotors on my Duetto with Dunlop brakes. I am having a similar issue. Unscrew (loosen) the rod at the top of the assembly (this is the venting adjustment for the pads to the rotor). This enabled me to get the pads in, but they seem too tight. I am planning to get at it again on Monday. Will post my findings then.
Tony
 

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Discussion Starter #3
Well I guess it's reassuring to have a brother in frustration. Yes, I'll adjust the link/equalizing rod to give adequate spacing but the fingers, in the current position, will be exerting a whole bunch of inward force. It's surprising to me the difference in thickness between new pads and spent pads- much greater than I've seen on other brands.
 

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Tony and Chuck, I hope these pictures help you guys out. I've had the same Dunlop brakes and pads on the Duetto since it came to me in 1984. The car also came with a new set of rear pads, that I have not used and they appear to be about the same thickness as the ones in Chuck's beautiful Dunlop brake photographs. I would not recommend bending anything. You can see how the parking brake cable appears to pull the bottom lever toward the center of the car in my photos; maybe that is the difference.

In more commonly used brake calipers, that have have hydraulics within the caliper, the piston seals act on the piston to retract it (fractions of a millimeter) when the brakes are released. I suspect that the seals in the Duetto's, hybrid external wheel cylinder, may act on the rod to relieve pressure on the brake pads the same way. However this system works and I have had no complaints with it, it does seem to work pretty well.

One thing that I would recommend doing while you are 'at it', would be to replace the bleed 'nipples and balls' with Quick Bleeder or Speed Bleeders. The part number I used is 12701. I've fought with bleeding the Touring Roadster drum brakes for over 25 years, only to realize that the 'archaic bleed nipples' were the problem. My early Duetto uses the same problematic bleed nipples as the Roadster; using a separate ball bearing under the nipple to seal the brake fluid in the wheel cylinder. The problem is, often the ball bearing gets stuck in the bearing 'seat' which makes bleeding difficult, if not impossible. I believe that sometimes fluid squeezes past the ball bearing that is trapping the air in the system. If the nipple uses a ball bearing, it'll have a flat bottom (a non tapered nipple). Use a magnet to extract the ball bearing before using a tapered nipple like those of the Quick or Speed Bleeder.

Mark
Dunlop Brake RR.jpg
Dunlop Brake.jpg
 

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The ratcheting system inside the larger arm is there to take up pad wear, adjusting the effective length of the top pushrod In order to do so.
Take the cover off the arm and watch it work, you should then see how to reverse (unwind) it, giving you enough clearance for the pads to slip in.
There should be no need to force/preload those gold-coloured springs to any significant degree, if at all.
 

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Discussion Starter #6
Thanks a bunch for the replies. Especially the bleeder screw tip.

I'm still stuck. As I see it, the gold colored springs are fixed so any significant pad thickness change is going to change preload one way or another- either inward or outward. Right now the fingers/spring are forcing the pads in toward the rotor.

To approach the problem another way, I removed the bolts anchoring the fingers so that they move freely. Then I adjusted the link rod that has the ratcheting nut attached and slipped the caliper over the rotor. With the pads wide enough to fit the rotor there is no way the bolt anchoring the fingers can be aligned without bending the fingers or exerting a whole bunch of inward pressure.
 

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Despite my suggestion to just keep extending the rod, I do seem to remember a similar conundrum when I did this, but I don’t think the answer was to undo those little springs.
It’s been too long ago for me to provide a definitive solution unfortunately. Hopefully, someone with more recent experience can chime in.
 

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OK I was able to change the rotor and install new pads in the left rear today. Here is what I found...
1. Remove the bar that holds the pads in place
2. pull the clevis pin on the adjustment rod - the brake snapped open
3. unscrew the rod to open the assembly completely
4. Pads came right out
5. check the brass lining on the caliper that locates the pad...mine was not positioned properly
6. remove caliper and install new rotor, reinstall caliper
7. install new pads...I had to remove some material as they were too tall to fit in caliper
8. turn adjustment rod to set pad distance from rotor
Note: the inner pad seems closer to the rotor than the outer pad
9. Use adjuster barrel in caliper to set pad distance from rotor at .5mm or 0.020"
10. Check handbrake for proper action...pump brakes to set everything
11. Recheck venting clearance for pads
My problem on the right side appears to have been caused by the caliper being difficult to freely move.
Tony
 

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Discussion Starter #9
Thanks for the info, Tony. Glad the install went smoothly.

After studying many pictures, including ones supplied earlier in this post, I decided my problem was that a previous owner had bent the fingers/springs inward. Don't know why, maybe to lessen pedal travel w/ worn pads. I bent them back to what I guessed was original and things seem to work fine.

Interesting that you needed to grind the pads- I had to do the same thing. One thing I discovered regarding caliper to rotor spacing is that shims were originally used, as required, under the caliper mount to center the rotor between the caliper
 
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