REAR disc "CALIPER setup HOW-TO" (e-brake/parking brake)

[hans j]

We have a van in the shop with the small car calipers. Park brake mechanism rusted solid. Can't actuate it with my hand at all.
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1986 Canadian Syncro Westy TDI - 1989 Syncro Single Cab - 2001 Audi S4 - 1981 VW Caddy ABA - 1980 VW Caddy EV - 1973 VW T-181

[Sodo]

[Sodo]

I took both calipers completely apart. Can't find any problem. Both actuators look the same, behave the same. Both advance 0.068 inches by lock-to-lock actuator rotation. looks good inside. Seals good, boots good (but they're only 30k miles).

========= OK, ONWARD TO SETUP ============

I put it all back together, and preset the pistons per the UKguys instructions. Kinda,,,,,, except a lot simpler. I ground the rust-rim off the disc so I could slide the caliper easily onto the disc. Inserted the brake pads into the caliper. Then by measurement, adjustment, etc I set the pistons just a little wider than the disc. Then with a screwdriver, was able to easily adjust the final amount to be about 1mm or less (wider than the disc thickness).

See pics below, it's pretty easy to do.

Disconnect your brake cables and make sure the caliper's cable brake actuators are all the way "out" (as their spring drives them).

Measure the dic thickness and set the pads appx that wide. You can see the distance from the piston to the pad

Tip the pad outward to get access to the piston.

With a waterpump plier, turn the piston to drive it outward. It's a course right-hand thread, it moves outward quickly.

Bolt the caliper onto the disc. Wiggle it on its sliders and watch the clearance between the disc and the pads. With a screwdriver you can turn the piston a little tighter if necessary, until there's less than 1 mm clearance between pads and disc.

Connect the brake lines. Open the bleeders and let the disc calipers slowly fill by gravity. When the fluid starts to run out of the bleeders, perform your final bleeding process, and your footbrake should be firm.

Hook up the cables, and adjust your brake handle to the desired number of clicks. There are 12 clicks. Internet legend prefers the low count (3 clicks) but the vanagon handle offers 20% more stopping power on the high side (9-12 clicks). The middle is OK too.

The result?

I now have a parking brake! It's been YEARS. Not a chance in heck it will skid the tires, but it holds on a hill like this:

Just barely. You can bet I put it in granny before getting out to take the pic. But it did HOLD, a vast improvement.

I tried a 20mph to zero stopping power test. Drive 20mph (by GPS speedo). Watch foe a pothole or manhole cover. When front wheel thumps, pull the brake hard. I did it twice, both times it took 72 feet "emergency stop" from 20mph.

So there ya have it folks, UK method translated to 'merkin.
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'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[ragnarhairybreeks]

Well done and excellent documentation.

Alistair
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'86 7 passenger syncro, converted to westy pop top, project still in progress
'82 westy, diesel converted to gas in '94, now gone...
https://shufti.blog/
Old address still works...
http://shufti.wordpress.com

[Christopher Schimke]

Right on! Thank you for taking the time to question, experiment and document all your trials and tribulations. It's super cool to see the fruits of your labor pan out in the end.
_________________
"Sometimes you have to build a box to think outside of." - Bruce (not Springsteen)

*Custom wheel hardware for Audi/VW, Porsche and Mercedes wheels - Urethane Suspension Bushings*
T3Technique.com or contact me at [email protected]

[dkoesyncro]

Awesome job, obviously I've been following this. Man your perseverance is unmatched! I say "keep on, keeping on"!

Thanks for your contribution to the vanagon community.

[Zeitgeist 13]

Good. I expect three more threads on painting rusty calipers, replacing cracked pads and the metaphysics of parking on a slope
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Casey--

'89 Bluestar ALH w/12mm Waldo pump, PP764 and GT2052
'01 Weekender --> full camper
y u rune klassik?

[WLD*WSTY]

I'm glad you've finally gotten the brakes you were looking for. Now, will better cables help even more? I can't wait to see your video of handbrake turns!
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'82 SyncroWesty, the first ever conversion.'06 Subaru 2.5L

[dobryan]

Yaaay!

The performance of the parking brake is basically the same as mine. I got there by luck I guess. 2009 Small Car rear disc kit too. I can pull six or seven clicks max.

What percent slope are you able to hold on?

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Dave O
'87 Westy w/ 2002 Subaru EJ25 and Peloquin TBD

"To travel hopefully is a better thing than to arrive." Robert Louis Stevenson

MD>Canada>AK>WA>OR>CA>AZ>UT>WY>SD
https://www.thesamba.com/vw/forum/viewtopic.php?t=620646

Building a bus for travel in Europe (euroBus)
https://www.thesamba.com/vw/forum/viewtopic.php?t=695371

The Western Syncro build
https://www.thesamba.com/vw/forum/viewtopic.php?t=746794

[Christopher Schimke]

So...something occurred to me last night: Do your brakes (or rather braking performance) feel any different now that you have gone through this adjustment procedure? The reason I ask this is because I'm having a hard time understanding how the parking brake performance can be so poor (previously of course) and and you could still have properly functioning rear brake calipers. In other words, if the piston that operates the parking brake is far enough out of adjustment that it is not allowing the parking brake to function properly, then it seems only logical that the main braking on the rear caliper(s) is not performing well either.

*EDIT*
I guess I should clarify that I am trying understand if it is possible to have the parking brake mechanism so far out of adjustment that it is not working properly and still have a perfectly operational brake caliper for the main braking system OR if the having the parking brake mechanism out of adjustment directly affects that calipers main braking performance.
_________________
"Sometimes you have to build a box to think outside of." - Bruce (not Springsteen)

*Custom wheel hardware for Audi/VW, Porsche and Mercedes wheels - Urethane Suspension Bushings*
T3Technique.com or contact me at [email protected]

[Sodo]

[cyrus #1]

I think the issue is the brake hydraulics are able to much more readily take up any "slack" in the system. The hydraulic piston has to be able to take up 1/4" to 1/2" for pad wear alone.

In comparison, sodo posted that full travel of the e-brake lever only advanced the mechanism .068". That isn't very much to compensate for wear or improper setup. If i remember correctly, i don't believe the system will self adjust unless it has resistance either.

If anything, i suspect the only side effect of the out of adjustment e-brake would be (very) slightly increased pedal travel.
_________________
1982 Westy TDI
2005 Jetta Wagon TDI
2005 Touareg V8

[Christopher Schimke]

[Sodo]

I'm curious too. I wish I had one of these still apart to study that. Here's a pic of the mechanism, sorry I don't have more details.

Error on image should read: "2) and 4) thrust springs"

That internal threaded post is dropped into the piston. The part has a seal at the bottom, that goes into a blind-hole bore at the bottom of the piston. Then the parts at left are dropped onto the post in the sequence numbered, and circlip engaged against spring-pressure. Callout 6) is just a "note" about the direction of the pressure-seal. The seal orientation energizes AGAINST footbrake hydr. pressure. It puzzles me what could be the function of that seal.

The friction of the spring-washers against that tiny 6-ball thrust bearing and the rubber seal, is all that prevents the threaded post from rotating. It turns easily with pliers but not fingers. I thought "too easily", but have nothing to compare to. Both left and right were "consistent" in their 'rotational friction'. Parts all appear to be 'in order' except perhaps the ball-brinelling. I was surprised that the little thrust bearing balls had brinnelled the surface. Note 'direction' of the brake hydraulic pressure seal below (into a bore on the piston). I'm trying to grok the function of that seal and its blind cavity below.

You may recall that I increased the lever arm +70% on my actuator (same as a 70% increased cable pull). A couple times yesterday I felt something like "slippage" which is either my cable housing (or plastic spacers) collapsing, cable itself stretching, or that center mechanism rotating (the screw backdriving it). Then I have to get under the van and twirl the little m6 center nut to return the clickety-click count to midrange again.

We're getting down 'tuit here. Pretty much need 10c or crazyvwvanman to get involved at this point. Or someone who understands how the proportioning valve works. Christopher you can prob figger this out.
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'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[Sodo]

Here's something. Takes some arm-waving - I'll try to type armwaving.

The center jackscrew pushes against those screwthreads but doesn't "pull". The jackscrew does NOT turn, it pushes only 0.068" (1.5mm). The screwthreads are "steep" but with the center post jammed up against the backside of the piston head, nothing turns on the threads.

Upon releasing the parking brake,,,

The spring washers ensure that the jackscrew arrangement cannot prevent the piston from advancing to squeeze the (minute travel to the) pads. At first assembly, lets say you just pumped the piston outward with the footbrake hydraulics. This causes the center post to rotate (against springwasher friction) as it's driven along the non-rotating jackscrew to the end (pads tight). So it ends up PULLING against the springwashers. WRONG. You want it biased to the OTHER side, with springwashers shoving the post AGAINST the brake piston, to initiate the auto-adjust.

It seems unlikely that Smallcars instructions to 'pull the brake handle 20-30 times' could back-drive the center post onto the jackscrew. It seems like it could work on some calipers, and NOT work on others. Manually advancing the jackscrew thread with a water pump plier doesn't leave it to chance.

I don't yet understand if 'adjustment' (as the pads get thinner) occurs by hydraulic actuation, by parking brake actuation, or both.

As the piston advances forward into the thinning pads, it compresses the two spring discs (pulling on the jackscrew). Eventually "topping out" against the circlip. At this point it pulls the center post downward along the jackscrew. The center post unit must rotate to move down the jackscrew. Which it does. It arrives at it's new position, and due to the friction it remains there.

It seems like if you were to adjust the handbrake too tight (the low clicks custom) then the jackscrew will always be partially extended, and the slop this contraption needs to self-adjust (advance) may be impaired. It just can't pull as hard because the jackscrew is partially extended. Not sure about this....but it seems you want the jackscrew to retract fully always.

I'm not sure what the effect of wear on the interfaces that advance the jackcrew post. It could be a factor in why some brakes work better than others.

Here's more pics and info.

This parts diagram is page 2 of Lucas bulletin XZB137 I don't understand the relationship between the Lucas caliper and the Girling 4143.

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'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[Christopher Schimke]

[Christopher Schimke]

_________________
"Sometimes you have to build a box to think outside of." - Bruce (not Springsteen)

*Custom wheel hardware for Audi/VW, Porsche and Mercedes wheels - Urethane Suspension Bushings*
T3Technique.com or contact me at [email protected]

[hans j]

I just can't help but think something was wrong with your calipers from the beginning. I've done hundreds of rear brakes on VW/Audi and NEVER had to advance the piston manually for the park brake to work.
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1986 Canadian Syncro Westy TDI - 1989 Syncro Single Cab - 2001 Audi S4 - 1981 VW Caddy ABA - 1980 VW Caddy EV - 1973 VW T-181

[Sodo]

[hans j]

When I replace rear brake pads and rotors, I pump the brakes until firm and then give a few yanks on the hand brake to make sure it holds.

And to push them in, I use this tool https://www.amazon.com/Zdmak-Brake-T10165-Volkswagen-BONUS/dp/B00XKN6I46 (but it was a lot more expensive from the dealer!). If the caliper doesn't retract correctly, a new one gets sold and then it works just fine.
_________________
1986 Canadian Syncro Westy TDI - 1989 Syncro Single Cab - 2001 Audi S4 - 1981 VW Caddy ABA - 1980 VW Caddy EV - 1973 VW T-181