dual circuit brakes

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63CorvairSplit
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Re: dual circuit brakes

Post by 63CorvairSplit » Thu Jun 06, 2013 6:11 pm

Has anyone fitted the 944 M/C? I am fitting 944 discs front and rear. I also got the M/C and servo from the donor car so was planning on using the porsche M/C but the servo looked a bit of a pain toi get fitted right.

thanks, mike
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wicker
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Re: dual circuit brakes

Post by wicker » Fri Jul 12, 2013 5:02 pm

So i bought a bay 71-79 ATE MC (without servo)

My problem is the holes are 100mm apart on the MC and the CSP reservoir has 85mm spouts apart.

Can i just find another reservoir with 100mm spouts apart and bobs your uncle or am i in it till my knees and will need a new MC? :evil:

PLEASE somebody help :?

Thanks
eric.
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CapeTown62
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Re: dual circuit brakes

Post by CapeTown62 » Wed Jan 08, 2014 6:40 am

Hi all,

Apologies if there is an answer to this here already: I had a good look but couldn't find one.

I've just upgraded to dual circuit and CSP discs on the front (had a scary total brake failure a while back: fortunately flat road in a little dusty town so no damage done) and was about to put my old front drums and shoes up for sale when I wondered if there'd be any benefit to fitting them at the back. Two slave cylinders per drum should provide more powerful braking than one, right?

Anyone done this?

Cheers,

Mike
Cheers,

Mike
1962 11 Window RHD bus
Cape Town, SA

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type21f
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Re: dual circuit brakes

Post by type21f » Wed Jan 08, 2014 6:51 pm

I have no idea BUT on modern cars they fit brake limiters...a ball bearing rolling up a slope caused by deceleration to cut the flow of brake fluid to the rear brakes and prevent them locking up. The brakes are designed to have more stoping power at the front and less at the rear. Hence modern cars with disc brakes at the front and drums at the rear..
From a personal point of view I upgraded brakes all round on a drum mini but fitting AH sprite bigger bore cyliders in the place of mini ones and that did improve the overall stopping, but i did not change the overall balance..

I do not think it will be possible to do what you want because of the requirement for the hand brake mechanism anyway..
There may be bigger cylinders on other models to substitute.
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Re: dual circuit brakes

Post by CapeTown62 » Tue Jan 14, 2014 1:02 pm

Thanks for the in T21... Found another reason this won't work: the front backing plates and drums are simply not designed to work with the rear suspension and drive shafts. So looks like I'll stick to the standard drums at the back for now and the new discs up front. Still bound to be a LOT better than the stock drums all round. So... For Sale: one set of used 1962 Type 2 drums complete with backing plates and shoes!


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Cheers,

Mike
1962 11 Window RHD bus
Cape Town, SA

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MYTDUB
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Re: dual circuit brakes

Post by MYTDUB » Sat Jul 26, 2014 7:53 pm

wicker wrote:So i bought a bay 71-79 ATE MC (without servo)

My problem is the holes are 100mm apart on the MC and the CSP reservoir has 85mm spouts apart.

Can i just find another reservoir with 100mm spouts apart and bobs your uncle or am i in it till my knees and will need a new MC? :evil:

PLEASE somebody help :?

Thanks
eric.
I thinks I read somthing some where that the volvo reservoir can be used! Don't ask which volvo!....
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eliotc
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Re: dual circuit brakes

Post by eliotc » Fri Aug 29, 2014 7:43 am

I just want to add my 2 pennies worth to this thread, hopefully in an attempt to prevent someone totalling their bus or even killing themselves.

I've owned my 1960 bus for 6 years and in this time I've resisted the urge to go to dual circuit....preferring to stay stock where possible...BIG MISTAKE!!! Last week, coming down a very steep hill in a residencial area I had total break failure....hit the pedal and nothing, gaining speed I tried the hand brake (adjusted properly), also nothing.....dropped down to first, big screech of the tyres but still unable to stop.....Beeping my horn frantically at the woman doing a 3 point turn 50m ahead of me, she got out of the way just in time....my 19 yr old son had the passenger door open ready to bail. Fortunately the road levelled out and amazingly we eventually came to a stop without hitting anything. It was only after that it dawned on me how lucky we were......2 minutes later we would have been on a main road and maybe even a high speed carriageway. So needless to say we are in the process of fitting a dual circuit M/C.

What is interesting is how this happened and I wonder if anyone has had a similar experience. The rear brakes are less than 4k miles old and on inspection the linings on one of the rears had separated from the shoes, creating a gap big enough for the wheel cylinder to expand beyond it's limits and leak fluid - hence why the hand brake did bugger all. The linings have plenty of meat on them but they were glued in place by 5 or 6 dots of glue. We cleaned everything up and they are now riveted in place. All parts came from VW Heritage.

M/C is going on today plus spacer etc etc.

Has anyone experienced similar problems with nearly new shoes and is there a particular brand that we should be buying, that are either riveted on or secured with a decent quantity of glue? And finally if you are still running a single circuit M/C, change it before you drive your bus again otherwise it's only a question of time before your sharing a similar story and likely with far more severe consequences.

BTW....1960 bus with IRS rear end and Bay 68/69 rear brakes.
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eliotc
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Re: dual circuit brakes

Post by eliotc » Fri Aug 29, 2014 7:02 pm

Following on from this.....a bit of help please.....
Fitted the dual m/c with front brakes connected to the ports furthest from the pushrod, one other to the rear leaving one for the brake light switch as per CSPs fitting instructions. On bleading the system the rears are completely free of air but both fronts have thousands of minute bubbles in the fluid, which I cant seem to get rid of for the life of me. But bleeding the system for about 4 hours now. The result is practically no brakes and a soft pedal. I can hear the shoes expanding and hitting the drums as the pedal is pumped. There are no apparent leaks in the system. Going to try adjusting the shoes tomorrow but is there anything that im missing?

Been bleeding the brakes with the tried and tested method of a tube, jar of fluid and a friend pressing the pedal 3 times then holding on to the 4th whilst i slack the nipple and expel the air. Started with the rears before doing the fronts. Any suggestions?
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type21f
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Re: dual circuit brakes

Post by type21f » Fri Aug 29, 2014 8:14 pm

I did not bleed my brakes...I have not worked on my system..so take this as a report on a cause..
One of my NEW wheel cylinders...ATE....labelled had a problem with the seat of the bleed screw It did not seat so air was drawn in from there..
A complaint and a replacement cured the leak..
ONE OF MANY POSSIBLE BRAKE ISSUES..

When I had a mini...I used to replace by clamping the flexible and then expelling the air out at that end with never an issue..
So i must say I have not personally had problems drawing air in..

One problem I did had re-using OG parts was having to machine the drums to be true...So the shoes actually touched the drums..
Hoping they are OK..
Last edited by type21f on Fri Aug 29, 2014 8:14 pm, edited 1 time in total.
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eliotc
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Re: dual circuit brakes

Post by eliotc » Wed Sep 03, 2014 6:31 am

*SOLVED*

I was being an idiot - pushrod wasn't adjusted correctly so not pushing the piston in fully - adjusted with correct 3mm of play, shoes adjusted and continued to bleed brakes. Got there in the end and nearly threw myself through the windscreen when I tried the brakes - brakes like a modern car now (well, almost!!).

Would still be interested to hear any reports re new brake shoes falling apart after only a few thousand miles.

Thanks.
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Re: dual circuit brakes

Post by susta » Sat Sep 06, 2014 7:02 pm

Hi ,
Just thought I'd ask, spoke to Jim about his indirect servo, which I'm about to set out, and raised the point about proportional valves , don't use them was his response . Any feed back re this issue?

Cheers
Steve


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Re: dual circuit brakes

Post by kombi niko » Tue Jan 06, 2015 12:32 am

Hay guys with those rubber bungs do they go in the unit first then push the plastic reservoir in place?

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8 8US
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Re: dual circuit brakes

Post by 8 8US » Tue Jan 06, 2015 7:24 am

kombi niko wrote:Hay guys with those rubber bungs do they go in the unit first then push the plastic reservoir in place?
Did the same job last night, I fitted the rubber bungs to the reservoir then installed it on the master cylinder, I couldn't get the reservoir on the other way and was worried about bending the plastic.
Richard

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Re: dual circuit brakes

Post by Richierich » Fri Jan 09, 2015 8:49 pm

eliotc wrote:Following on from this.....a bit of help please.....
Fitted the dual m/c with front brakes connected to the ports furthest from the pushrod, one other to the rear leaving one for the brake light switch as per CSPs fitting instructions. On bleading the system the rears are completely free of air but both fronts have thousands of minute bubbles in the fluid, which I cant seem to get rid of for the life of me. But bleeding the system for about 4 hours now. The result is practically no brakes and a soft pedal. I can hear the shoes expanding and hitting the drums as the pedal is pumped. There are no apparent leaks in the system. Going to try adjusting the shoes tomorrow but is there anything that im missing?

Been bleeding the brakes with the tried and tested method of a tube, jar of fluid and a friend pressing the pedal 3 times then holding on to the 4th whilst i slack the nipple and expel the air. Started with the rears before doing the fronts. Any suggestions?
I think with dual circuit, VW reckon you bleed the fronts first rather than start at cylinder farthest away and work back. I've just rebuilt brakes on my 67 and am about to fit new master cylinder and a few guys on TheSamba pointed this out.

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Re: dual circuit brakes

Post by e m p i » Fri Jan 23, 2015 5:39 am

8 8US wrote:
kombi niko wrote:Hay guys with those rubber bungs do they go in the unit first then push the plastic reservoir in place?
Did the same job last night, I fitted the rubber bungs to the reservoir then installed it on the master cylinder, I couldn't get the reservoir on the other way and was worried about bending the plastic.
Yup that's correct, bungs onto reservoir then push the reservoir inc bungs into the master cylinder. You can smear a little brake fluid in the bungs if it helps.

Cheers, Lee.
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