Dunlop rear calipers...what am I missing? - Page 2 - Alfa Romeo Bulletin Board & Forums
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post #16 of 31 (permalink) Old 08-17-2012, 05:37 PM
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Wink A few facts....

are in order here !

This GTA is a multi championship winner in Euro FIA races. Notice that it still wears the original Dunlop brakes.

In Europe, these are known to stop better than the ATEs and with proper maintenance are completely reliable. All parts are available new.

So don't ditch them just because you don't have the info for setting them up !
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post #17 of 31 (permalink) Old 09-07-2012, 10:36 PM
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Understanding 105 Series Dunlop rear brake calipers

I was tempted to avoid posting on this thread but due to some of the negative comments and mis-information regarding these Dunlop rear calipers .. I'm diving in.
Most of the negativity toward this Dunlop design is due to the lack of understanding of how they operate. Most of the posts here - excluding the initial post - contain accurate information regarding how they work.

Utilizing Biba's pic of a RIGHT rear caliper as mounted on an axle I will attempt to explain the operation of these marvelous mechanical devices.

The yellow arrow depicts the hydraulic force conveyed from the Master Cylinder to the slave cylinder where it is transformed at the piston to a mechanical force which is transmitted through the actuating rod (yellow w/red dots) to the pin at the lowest point of the alloy lever. This lever pivots at the pin (obscured but encircled by white dots). The force on the alloy lever works in two ways .. it pushes (pink arrow) on the inside lever which pushes on the inner brake pad while simultaneously applying an equal pulling force via the threaded rod (green arrow) to the outside lever which bears against (light blue) the outer brake pad. In doing so, the return torsion spring (red) tension is overcome and the brake pads make contact with the disc or rotor. When the hydraulic force is released .. the return torsion springs retract the brake pads.

Pulling the parking/emergency brake applies a force in the direction of the dark blue arrow that acts on the link which pivots at the pin (white w/red dots) thus applying said force to the alloy lever allowing brake actuation in the same manner.

The beauty of this design is in eliminating additional brake shoes, springs, drums, etc.. a complete caliper weighs less than 6 pounds/2.7kg

While hydraulic leaks cannot reach the brake pads .. as this pic demonstrates .. failure of the axle seals can compromise the brake system.
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post #18 of 31 (permalink) Old 09-07-2012, 11:40 PM
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:::C&C PARTS:::

these guys have absolutely EVERYTHING re Dunlop brakes in stock.
Mail them. This is one of the most FANTASTIC companies around. We just sent off some 6C2500 brake parts. Duh. In stock, off the shelf. No sweat.
Dunlop rear calipers? In stock, new. No problem. Very realistic prices too, I continue to be surprised. They do international business so can help.
Not a plug for CC, but as a useful hint. I LOVE this shop, really.


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post #19 of 31 (permalink) Old 09-08-2012, 08:37 PM
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Nicely Done

Nice explanation, GTD!

Chuck

'65 Giulia Sprint GT; '76 Alfetta GTV; '71 Fiat 124 Spider (early 1438cc); '71 Fiat 124 Spider (late 1608cc); '86 Callaway Twin Turbo GTV6 and '91 164S (with new owners)
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post #20 of 31 (permalink) Old 10-11-2012, 03:06 PM Thread Starter
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Handbrake adjustment: I've finally hooked up the handbrake and fully adjusted the cable and it isn't even close to being tight. I double checked the part number and it is 'apparently' correct.

I've not re-adjusted the operating levers, but unless only a few turns on them really makes a difference, I'm more-or-less at the end of my rope.

I'm waiting for the new, correct fluid reservoir, so have not bled the brakes, but strongly doubt if that makes any difference to the handbrake adjustment

I'm guessing I need about a 2" - 4" shorter main hand brake cable.

Comments?

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post #21 of 31 (permalink) Old 10-13-2012, 07:32 PM Thread Starter
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I'm surprised how so few turns on the pull-rod can take up the slack on the main brake cable.

There was a comment on how critical it is to make sure that both of the rear brakes are adjusted evenly. The only thing I can think of is to make sure the pull-rods are out the same amount on both sides.

Or is there another way to know they've been adjusted 'properly'? Of course, once the GTV is driven, that will be the determining factor.

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post #22 of 31 (permalink) Old 10-30-2012, 02:07 PM Thread Starter
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I should have listed my brake bleeding woes here: With a great deal of bleeding brakes with a Mity-Vac - which has always worked for me in the past - I have a good half brake and when pumped a few times almost a full solid one, then fades.

I'm getting nothing but big bubbles and little fluid from the four bleed screws. I've had bubbles like this on my own car and still had a solid brake pedal.

Accept that everything is new and that I've bled a large bunch of brakes - but never with these rear brakes. Most all of the possible adjustments on the brakes and hand brake cable are 'out' as far as they will go.

With the pedal propped down, I have solid brakes on the front and left rear. The right rear still turns fairly easily. I will admit when I was setting them up I had to make the left side upper push-rod a few turns 'larger' than the left side. Each side is about a turn from undoing from the serrated gear.

Even if I undo the left side in a turn and the right side out a turn (and it doesn't fall off), I'm doubting this will solve all of my problems.

I have had a few leaks but I've gone over everyone of them with the finger test and there are no longer any leaks.

I'll add that with the hand brake pulled halfway I have solid brakes on both sides - and yes I'm aware the pads are being operated in a different manner than the hydraulic way.

Is there a special bleed process for these brakes?

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post #23 of 31 (permalink) Old 10-30-2012, 03:30 PM Thread Starter
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Update, I'm aware I had the turn out and in mixed up. I now have the two rears pretty closely balanced gong by how hard they are to turn each with pedal propped down.

However, the length of each upper push-rod is uneven with the right one being about 4-5 mm shorter than the left when at rest. When I was assembling the calipers, I noticed there was a difference between the two calipers. Each looked fine, but weren't completely matching. I'm going on the basis that as long as they are 'pressing' the same amount, that's what matters. And as mentioned, both of the wheel cylinders are new.

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post #24 of 31 (permalink) Old 05-05-2014, 09:38 AM
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handbrake cable for Dunlop brakes

Hello All

The information on the Dunlop brakes has been most useful so thank you. Does someone have the copy of the Dunlop service manual mentioned in the thread - Italian version ?
Also, can someone explain how the handbrake takes up the tension on the right hand caliper , my left hand caliper takes up quickly enough when pulling up the handbrake but the right one does not follow as quickly, what causes the right hand 'short' cable to pull if not the direct cable ? Another request does someone have the correct lengths for 'short' left and right cables and the longer cable that fixes to the handbrake mounting point ?

Thank you
George
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post #25 of 31 (permalink) Old 05-10-2016, 01:26 PM
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Wow, thank you so much for this info bud. Starting a Dunlop brake rebuild soon.
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post #26 of 31 (permalink) Old 03-13-2017, 03:22 PM
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Quote:
Originally Posted by 39cub View Post
The little pistons came out without issues, but I sent the slaves out to be brass sleeved, just as a "while you're at it" measure. (I hate to do things twice...)

New seals and dust boots were tough to find. But there are some genuine kits on Ebay right now, so I'd say GRAB some while you can.

ALFA ROMEO GIULIA 1600 DUNLOP GIRLING REAR WHEEL CYLINDER REBUILD KIT NEW! | eBay

I bought some from this guy, no problems. (Note that some of the slaves used a circlip instead of the metal "cap" to contain the little piston.)

Chuck

Oh, that's Eastwood's brake fluid resistant gray paint, applied after a phosphoric acid etch after bead blasting and degreasing.

I am trying to locate the dust seals for the brake cylinders and the brake assy for the Dunlops on my 1964 GT Sprint ... please help..!!!
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post #27 of 31 (permalink) Old 03-13-2017, 04:04 PM
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post #28 of 31 (permalink) Old 03-20-2017, 07:49 AM
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Quote:
Originally Posted by Cali67Duetto View Post
Wow, thank you so much for this info bud. Starting a Dunlop brake rebuild soon.
Found these diagrams
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File Type: pdf dunlopdiagrams20170116 (1).pdf (3.00 MB, 21 views)
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post #29 of 31 (permalink) Old 03-20-2017, 10:31 AM
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Originally Posted by George View Post
Hello All

The information on the Dunlop brakes has been most useful so thank you. Does someone have the copy of the Dunlop service manual mentioned in the thread - Italian version ?
Also, can someone explain how the handbrake takes up the tension on the right hand caliper , my left hand caliper takes up quickly enough when pulling up the handbrake but the right one does not follow as quickly, what causes the right hand 'short' cable to pull if not the direct cable ? Another request does someone have the correct lengths for 'short' left and right cables and the longer cable that fixes to the handbrake mounting point ?

Thank you
George
Attached is the PDF file in Italian
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File Type: pdf Dunlopb Brake Manual.pdf (3.37 MB, 22 views)
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post #30 of 31 (permalink) Old 03-21-2017, 05:21 PM
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Spot on I am amazed how well those brakes work when properly set up, several friends tried to talk me into a conversion kit...Hell no ...my Feb 11, 1964 production Scalino is as the day it was built....
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