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Rear disc upgrade = NO parking brake!
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insyncro
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PostPosted: Tue Dec 02, 2014 9:21 am    Post subject: Reply with quote

These gents have over 200HP and vans that weigh more than most as they are expedition vehicles.
Each seems very happy, but has a "need" for line locks off road.
It is super overkill to be used as a parking brake in the city.

IIRC, these systems are electromagnetic, so if your battery fails or runs low, no more line lock.
I am sure other systems are available, but when I looked into more, I opted for bias control over line locks as my custom cables will hold a Syncro Westy, even with one wheel off the ground in its place.
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Sodo
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PostPosted: Tue Mar 15, 2016 7:21 pm    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

Working on this problem further. For the sport of it. I extended the caliper actuator lever to increase the force on the brake pads.

In a different thread it was discussed that perhaps the disc brakes need higher cable tension than the Vanagon parking brake lever can provide.

Cable tension varies 22% depending where you like your clicks. 40 lbs pull on the Vanagon brake handle generates:
-- 273 lbs tension on the equalizer bar if adjusted to tight at 3 clicks
-- 334 lbs if adjusted to tight at 12 clicks.

So that's the range of tension available. The equalizer divides this 273-334lbs appx half to each disc. That's 137-167 lbs at each caliper's lever arm. Lever arm is 1.625" long, thus 40 lbs on the parking brake handle generates 19-22 ft lbs "torque" at the disc brake actuator. For those who have run a torque wrench,,, 19-22 ft-lbs is not very much. Pretty likely there is a significant mismatch between what the Vanagon parking brake handle puts out, and what the disc brake requires.

Image may have been reduced in size. Click image to view fullscreen.


I cut/welded/extended the arm 1 1/8" (29mm) longer and moved the cable mount outward too. This will provide 1.7x the torque , or 32-37 ft lbs "torque" at the actuator. Maybe braking power will increase. With luck. Extending the crank at the calipers increases the braking pressure without increasing cable tension which is a better solution because it doesn't overstress OEM cables & mounts.

Also added a spring for better cable return as the grease dries out. Cables are greased and slide nicely at the moment. But it may be a couple weeks before the van's driveable.

Image may have been reduced in size. Click image to view fullscreen.


Cable housing re-locator bracket.
Constructed of 3/8" thick steel, 1/2" hole, 12mm stud welded in.

Image may have been reduced in size. Click image to view fullscreen.


This pic is the normal brake actuator lever/bellcrank, as installed on a Vanagon (Smallcar.com kit using "Audi 200" rear discs)

Image may have been reduced in size. Click image to view fullscreen.


Actuator lever extended for more torque.
The bracket can be bolted on.

Image may have been reduced in size. Click image to view fullscreen.

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Last edited by Sodo on Wed Mar 23, 2016 10:06 pm; edited 6 times in total
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ALIKA T3
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PostPosted: Tue Mar 15, 2016 9:27 pm    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

Looks great on paper and pictures!!

What part number are these calipers?

I have the parking brake lever inline with the van, not perpendicular like you do.
I still don't know how to solve that, makes me want to go back to drums after the bad parking brake power I keep reading about.

Hopefully your results will be encouraging to me Wink

Aloha!
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furrylittleotter
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PostPosted: Tue Mar 15, 2016 9:39 pm    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

Interesting work you have done! I always wondered why Mark always said you need to not tension the cable too tight and you explained why perfectly!

I wondered if you have seen these:http://www.speedwaymotors.com/E-Stopp-Electric-Emergency-Brake-Kit,65217.html?gclid=CPqX6MyvxMsCFRVsfgod1qsOrQ

I considered using them on my middle conversion but opted for a pulley setup instead.

Any idea how many pounds of tension they could produce?

While they aren't true" emergency" brakes I bet they could would work for this application as parking brake actuators

Neil2
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Sodo
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PostPosted: Tue Mar 15, 2016 11:56 pm    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

furrylittleotter wrote:
Interesting work you have done! I always wondered why Mark always said you need to not tension the cable too tight and you explained why perfectly!


Who's Mark? He's right. The 3-clicks rule is so a tech can install brakes and let the van go home with the client, where they don't drag but as they wear in the handle arrives at a proper early stroke position, ready for further brake lining wear and self adjust.

I wonder if there's enough lever movement for the brakes to self-adjust if you're always taking up the nut at the equalizer (in pursuit of the 3-clicks). In any case that's for OEM drum brakes which nobody reading this thread has.

furrylittleotter wrote:
I wondered if you have seen these: http://www.speedwaymotors.com/E-Stopp-Electric-Eme...fgod1qsOrQ

Any idea how many pounds of tension they could produce? While they aren't true" emergency" brakes I bet they could would work for this application as parking brake actuators


Their FAQ says 600 lbs (the stall force) which is about double of what the Vanagon parking brake handle produces. 600 lbs oughtta work better than 273-334 lbs. Very Happy That electric cable-puller will double the tension on the cables, which could be too much, you'd prob have to get bigger cables too.
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flomulgator
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PostPosted: Sun Apr 03, 2016 10:14 am    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

Alika,
I was addressing my last remaining safety item on the van yesterday, replacing OG brake flex lines with new stainless steel. Brushed the crud off the calipers to inspect them, and snapped this pic (same Smallcar setup as Sodo).

Image may have been reduced in size. Click image to view fullscreen.


In case it's not legible,
Brand: Girling
Part #: 32 32 23 93/4
side stamp: 4143
trademark stamped: V.A.G.
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flomulgator
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PostPosted: Sun Apr 03, 2016 10:38 am    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

Possible issue, rebuild of similar caliper (although his problem was handbrake sticking on:
http://www.audiworld.com/forums/audi-100-a6-c4-platform-24/rear-caliper-rebuild-guide-2770104/
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PostPosted: Sun Apr 03, 2016 10:47 am    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

And if contamination is an issue and don't want to rebuild, I believe (but can't be 100% certain), that these are the calipers Smallcar used. None of the stamped numbers line up, but maybe those are just serials? Looks the same as far as I can tell with these limited photos:

http://www.rockauto.com/en/catalog/audi,1990,200,2...kit%2C1720

Importantly, it HAS to be the "200 Quattro Sedan". All of the other models have the e-brake longitudinal to the disc (like Alika's, mabye?), whereas the sedan alone has the ebrake connecting perpendicular to the brake. This part page shows that in the pictures:

http://www.rockauto.com/en/moreinfo.php?pk=2053504&cc=1007198&jsn=20&jsn=20

will need to go to the top link to buy both sides. Of course, they are the most expensive offering by far.

Also while I'm at it, here are the correct bleeder screws. My fronts were badly corroded.
http://www.rockauto.com/en/moreinfo.php?pk=587011&cc=1007198&jsn=10404
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ALIKA T3
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PostPosted: Sun Apr 03, 2016 11:38 am    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

Hello!

thank you for your answer!

yes, I think mine were from a Passat. Damn it!

I think I'm gonna leave the disc brakes were they are now (Syncro project/donor) and keep the drums for now on my new Syncro project.

I can re-use and solve the problem when I install these on another van one of these days when I have more time on hand.

Cheers!
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PostPosted: Mon Apr 04, 2016 3:22 am    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

This is my rear disc setup on my 1990 T3, calipers, rotors and pads all from VW T4 Eurovan 1994 to 1997 in Aus. Uses standard T3 handbrake cable, rotors are 280mm and handbrake works great.
Image may have been reduced in size. Click image to view fullscreen.


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Sodo
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PostPosted: Mon Apr 04, 2016 8:38 am    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

Sodo wrote:
This pic is the normal brake actuator lever/bellcrank, as installed on a Vanagon (Smallcar.com kit using "Audi 200" rear discs)

Image may have been reduced in size. Click image to view fullscreen.


Actuator lever extended for more torque.
The bracket can be bolted on.

Image may have been reduced in size. Click image to view fullscreen.


Luckyphil the long actuator arm on your T4 Eurovan disc looks much better suited to the low cable-tension that the Vanagon parking brake handle generates.
Can you try the "Disc brake test" and report back? Very simple test, flat ground, rear on ramps, Yes or No. Would be nice to know if any disc brakes can hold on a ramp (the OEM drums can). "Details" are always appreciated (after the yes/no) such as wheel size.

Image may have been reduced in size. Click image to view fullscreen.

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....KTMs, GasGas, SPOT mtb
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PostPosted: Mon Apr 04, 2016 2:03 pm    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

Will give it a go on the weekend. Handbrake is holding well in normal driving and parking situations and am happy so far but will let you know.
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PostPosted: Tue Apr 05, 2016 2:17 pm    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

If you would like further details of this conversion feel free to contact Mark via email at [email protected]
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Sodo
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PostPosted: Fri Apr 29, 2016 7:40 am    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

Sorry it took so long to test this. The mod helps a lot, now there is detectable parking brake-hold. Tested on a ramp (the parking brake test thread) it holds but barely. Also the van hasn't been driven much in 10 months, I will check again as the brakes wear in.

Image may have been reduced in size. Click image to view fullscreen.

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PostPosted: Fri Apr 29, 2016 8:20 am    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

It's now going to take more lever pull to move the park brake lever on the caliper the same distance. I would add more spacer to the bowden brake cable and return the lever to it's original length.
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PostPosted: Fri Apr 29, 2016 9:09 am    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

hans j wrote:
It's now going to take more lever pull to move the park brake lever on the caliper the same distance. I would add more spacer to the bowden brake cable and return the lever to it's original length.


Hans, thanks for the interest. Did you mean to write (same distance or) same angle"? Same distance is not descriptive of the goal, as input and output of a cable is always the "same distance". "Increased clamping power" from this "same distance" is the intent of the modification. Not sure why you recommend against it, as yesterday's test suggests the lever needs to be lengthened further.

For "more spacer" I can just twirl the nut on the equalizer bar to lower the handle position but that goes the wrong way - a lower handle position (less clicks) actually decreases cable tension.

If by "return the lever to it's original length" you mean "put the drum brake back on" that's a way to get a parking brake. I envy your drum brake for its parking. I've spent the $1100 on this disc brake kit but will try a few more tricks to make it work (before throwing in the towel). I suspect there are a LOT of other disc brake members who would like to have a parking brake with their upgrade. Cool
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PostPosted: Fri Apr 29, 2016 2:05 pm    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

Sodo wrote:

Hans, thanks for the interest. Did you mean to write (same distance or) same angle"? Same distance is not descriptive of the goal, as input and output of a cable is always the "same distance". "Increased clamping power" from this "same distance" is the intent of the modification. Not sure why you recommend against it, as yesterday's test suggests the lever needs to be lengthened further.
I guess lengthing the arm will sort of take care some effects of a poorly adjusted bowden cable

For "more spacer" I can just twirl the nut on the equalizer bar to lower the handle position but that goes the wrong way - a lower handle position (less clicks) actually decreases cable tension.

The adjustment under the van won't change it. You have to actually put more spacer between the cable sheath and something solid (either the van body or the caliper). It's EXACTLY like a bike brake cable and won't work if there is too much slack in it. I think I mentioned this around page 1-3 of this thread.

If by "return the lever to it's original length" you mean "put the drum brake back on" that's a way to get a parking brake. I envy your drum brake for its parking. I've spent the $1100 on this disc brake kit but will try a few more tricks to make it work (before throwing in the towel). I suspect there are a LOT of other disc brake members who would like to have a parking brake with their upgrade.

I actually have home brew disc brakes that have worked fantastic since day one. Modified B5S4 calipers, welded the bracket straight to the bearing housing, URS6 276x25 front rotors, Mk4 park brake cables with conduit and washers for setting up the bowden properly, and custom vinyl covered stainless brake lines. It's somewhere in thread linked in my signature.

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PostPosted: Fri Apr 29, 2016 5:37 pm    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

It would need a spacer if the nut was maxed, and it's not. Not a setup problem, not related to the housing/bowden. There is no slack. Problem is the drum brake handle (inside the van) does not have the leverage to put enough tension in the cable.

It probably needs a little more leverage than I added, and I'm not sure how to get more (yet). Possibly the caliper mechanism inside is malfunctioning but the inceased holding power due to extending the lever is encouraging.
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'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb
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furrylittleotter
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PostPosted: Fri Apr 29, 2016 10:35 pm    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

Interesting updates.

Old question answered: the Mark,I was referring to is Crazyvwvanman.

He stated at some point that the the e brake lever requires a certain number of clicks to obtain maximum effectiveness.

Your testing confirmed that.

I may be incorrect but I believe by moving the pivot outward (the cable bracket) on your mod you reduced the effective torque of the modification.

I'd suggest you move it back to stock. If it binds you can add a barrel like a m/c hand brake lever has if you know what I mean.
Or you could make the cable bracket at a different angle.

Neil2
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Sodo
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PostPosted: Fri Apr 29, 2016 11:23 pm    Post subject: Re: Rear disc upgrade = NO parking brake! Reply with quote

furrylittleotter wrote:
Old question answered: the Mark,I was referring to is Crazyvwvanman.

He stated at some point that the the e brake lever requires a certain number of clicks to obtain maximum effectiveness.

Your testing confirmed that.


Ok that Mark, yes when he writes I read carefully too. Basically the brake handle geometry offers 22% higher cable tension at 12 clicks position than at 3 clicks position. I didn't test it, I just measured the geometry and calculated it.

furrylittleotter wrote:
I may be incorrect but I believe by moving the pivot outward (the cable bracket) on your mod you reduced the effective torque of the modification.


A cable is like a vector, it has a direction and a tension directly along its centerline. Whatever moves that vector away from the pivot increases the torque. Thus moving the bracket outward was necessary. The pivot has a "sweep too, you want the cable to be as far away from the pivot at the angular position (90degrees) when max torque is necessary. I can explain this much better with armwaving than typing and since you live in West Seattle now I'd be happy to do so someday. Cool
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....KTMs, GasGas, SPOT mtb
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