ausmini :: View topic - Dual brake master cylinder setup

So to confirm...

the rear proportional valve would or wouldnt be needed for this setup?

and if you did want a brake booster with 8.4" discs, would it go before the pressure regulator then??

thanks!!

I put a servo on a Clubby with tandem MC setup once, on front circuit only. It worked just fine.
Rear braking when you have front discs is severely limited anyway by the smaller 5/8" diameter cylinders, and the FAM valve or rear pressure limiting valve.

eg if you really stand on the brakes with a boosted Cooper S single line system, the servo can provide NO more rear braking than a stock MC would, as the rear cylinders can only get 370 or 340psi max, depending on limiting valve spring.

The Innocenti 1300 Coopers had a dual master & servo in the front brake line only.

Innocenti Cooper 1300:
http://www.mini-mayfair.net/daten/Innobrake.jpg

I use a similar setup, but with the later Rover proportioning valve (FAM7821) and T-spliter in the rear circuit. It works very well and the german TÜV approved it, so there's probably nothing wrong with it

Asphalt Special:
http://www.mini-mayfair.net/10zoll/splitbremse.jpg

-> limiter & T-Piece switched positions to the Inno setup.

Cheers,
Jan

I did a quick search on the FAM7821 that Asphalt was talking about just so i could get a visual on it and stumbled accross these 2 articles...

They explained a fair bit. Also came in handy.

http://www.minispares.com/Articles.aspx?ty=ad&aid=127

http://www.minispares.com/Articles.aspx?ty=ad&aid=129

arjay wrote:

These articles talk about potentially binning the std brake limiting valve (http://www.minispares.com/Product.aspx?ty=pb&pid=37054) and replacing it with the Minispares one (http://www.minispares.com/Product.aspx?ty=ar&pid=38406). What I don't understand though is unlike the std valve which has four ports, the Minispares valve only looks like it has has three ports. Is the Minispares bias valve only for use with a single circuit master cylinder - so that there is one line from the master cyl to the valve; and then one line to rear / one line to front?

To get things clear GT mowog, are you saying that in arjay's pic above, it could be set up so that '2' regulator can be removed and ensure that '5' is a pressure limiting valve? So with this setup, the '5' valve is adjusted to lock up the front wheels just before the rear. This whole brake set up thing is confusing :oops:

Author:	arjay [ Wed May 26, 2010 4:28 pm ]
Post subject:	Dual brake master cylinder setup
Ok. So one thing i cant quite seem to get because there are soo many topics covered on this but all of them are spread out, is the dual master cylinder and what is needed for the entire system. And by needed i mean, from the ground up brand new parts without missing anything. You'll see from the picture i have roughly drawn up what i understand the system should be. You have the dual master cylinder (yellow tag) which im not sure whether you use the brake fail switch on that or if thats why there is the hydraulic pressure regulator is there for. The hydraulic pressure regulator with the brake fail switch. Then the brake booster or servo whichever way you wish to call it. The T-peice for the front brakes, which then follow through to connector peices which join the rubber/stainless brake lines to the calipers. Now this is where i dont quite understand again.. If your using a dual master, what setup is used on the rear? I know that the brake regulator valve is for single systems but im not sure if i read people use it anyway. So if you have any information on any of this. And if any of my brake lines are incorrect which i think they are.. Please share! Thanks guys.

Author:	GT mowog [ Wed May 26, 2010 6:00 pm ]
Post subject:
You could do it that way, but you'll have reduced rear braking due to the booster being connected to the fronts only. In the late Rovers, they had a booster on the push-rod side of the M/C (like most convention cars these days) so it was mechanical assistance where as (say) the Cooper S had Hydraulic Assistance (these were single circuit). If your running 8.4"Discs or Drums up front then you don't need a booster. If your running 7.5" Discs up fron, they I would suggest a booster, however many people don't run them. It's possibly a personal preference thing. Otherwise, your drawing is correct, with the excetion of the Tee '4' is not needed at the regulator '2' has two ports for the front brakes (unless you have a late Rover one).

Author:	arjay [ Thu May 27, 2010 7:34 pm ]
Post subject:
So to confirm... the rear proportional valve would or wouldnt be needed for this setup? and if you did want a brake booster with 8.4" discs, would it go before the pressure regulator then?? thanks!!

Author:	GT mowog [ Thu May 27, 2010 7:47 pm ]
Post subject:
arjay wrote: So to confirm... the rear proportional valve would or wouldnt be needed for this setup? and if you did want a brake booster with 8.4" discs, would it go before the pressure regulator then?? thanks!! Proportioning / pressure regulating valve is required. 8.4" Discs no booster needed. <EDIT> If a booster was desired (and you really don't need one with 8.4" Discs) on a tandem (dual) circuit system, you would really need either;- 2 boosters, one in each hydraulic circuit, or A booster on the mechanical end of the M/C (as per late Rover). You could run with a booster in the front circuit only, before the tandem pressure valve or use a single circuit pressure valve (as per early cars), but either of these set ups would be way less than optimum.

Author:	Asphalt [ Thu May 27, 2010 8:23 pm ]
Post subject:
The Innocenti 1300 Coopers had a dual master & servo in the front brake line only. Innocenti Cooper 1300: http://www.mini-mayfair.net/daten/Innobrake.jpg I use a similar setup, but with the later Rover proportioning valve (FAM7821) and T-spliter in the rear circuit. It works very well and the german TÜV approved it, so there's probably nothing wrong with it Asphalt Special: http://www.mini-mayfair.net/10zoll/splitbremse.jpg -> limiter & T-Piece switched positions to the Inno setup. Cheers, Jan

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Dual brake master cylinder setup https://www.ausmini.com/forums/viewtopic.php?f=2&t=63300	Page 1 of 2

Author:	arjay [ Thu May 27, 2010 8:51 pm ]
Post subject:
Thanks a lot guys.. Cleared up a lot. Im sure it will be helpful for others in the future..

Author:	arjay [ Thu May 27, 2010 9:11 pm ]
Post subject:
I did a quick search on the FAM7821 that Asphalt was talking about just so i could get a visual on it and stumbled accross these 2 articles... They explained a fair bit. Also came in handy. http://www.minispares.com/Articles.aspx?ty=ad&aid=127 http://www.minispares.com/Articles.aspx?ty=ad&aid=129

Author:	drmini in aust [ Thu May 27, 2010 10:19 pm ]
Post subject:
I put a servo on a Clubby with tandem MC setup once, on front circuit only. It worked just fine. Rear braking when you have front discs is severely limited anyway by the smaller 5/8" diameter cylinders, and the FAM valve or rear pressure limiting valve. eg if you really stand on the brakes with a boosted Cooper S single line system, the servo can provide NO more rear braking than a stock MC would, as the rear cylinders can only get 370 or 340psi max, depending on limiting valve spring.

Author:	GT mowog [ Fri May 28, 2010 2:16 pm ]
Post subject:
drmini in aust wrote: I put a servo on a Clubby with tandem MC setup once, on front circuit only. It worked just fine. Rear braking when you have front discs is severely limited anyway by the smaller 5/8" diameter cylinders, and the FAM valve or rear pressure limiting valve. eg if you really stand on the brakes with a boosted Cooper S single line system, the servo can provide NO more rear braking than a stock MC would, as the rear cylinders can only get 370 or 340psi max, depending on limiting valve spring. On a crash stop, yes, this is 100% correct............... however, this set-up would fail RWC (at least in NSW) due to unacceptable brake balance between front and rear (Most RWC 'Blue Slip' Inspection Stations use the Plateronic Safe T Stop to test). Under more normal stops, there would be insufficent rear braking. In standard set up the standard mini brakes (and discs fare worse than drums) in tip-top condition only just get through. With boosted fronts only, a bigger rear wheel cylinder would help, while I haven't yet done the calculations, possibly a 3/4" rear wheel cylinder might be what is needed, along with (possibly) a custom rear wheel cyinder pressure shut off valve.

Author:	GT mowog [ Fri May 28, 2010 3:27 pm ]
Post subject:
Asphalt wrote: The Innocenti 1300 Coopers had a dual master & servo in the front brake line only. Innocenti Cooper 1300: http://www.mini-mayfair.net/daten/Innobrake.jpg I use a similar setup, but with the later Rover proportioning valve (FAM7821) and T-spliter in the rear circuit. It works very well and the german TÜV approved it, so there's probably nothing wrong with it Asphalt Special: http://www.mini-mayfair.net/10zoll/splitbremse.jpg -> limiter & T-Piece switched positions to the Inno setup. Cheers, Jan To maintain Front - Rear Brake Balance, these actually had an 11/16" rear wheel cylinders.

Author:	Mearcat [ Fri May 28, 2010 3:47 pm ]
Post subject:
arjay wrote: I did a quick search on the FAM7821 that Asphalt was talking about just so i could get a visual on it and stumbled accross these 2 articles... They explained a fair bit. Also came in handy. http://www.minispares.com/Articles.aspx?ty=ad&aid=127 http://www.minispares.com/Articles.aspx?ty=ad&aid=129 These articles talk about potentially binning the std brake limiting valve (http://www.minispares.com/Product.aspx?ty=pb&pid=37054) and replacing it with the Minispares one (http://www.minispares.com/Product.aspx?ty=ar&pid=38406). What I don't understand though is unlike the std valve which has four ports, the Minispares valve only looks like it has has three ports. Is the Minispares bias valve only for use with a single circuit master cylinder - so that there is one line from the master cyl to the valve; and then one line to rear / one line to front?

Author:	GT mowog [ Fri May 28, 2010 4:19 pm ]
Post subject:
Mearcat wrote: arjay wrote: I did a quick search on the FAM7821 that Asphalt was talking about just so i could get a visual on it and stumbled accross these 2 articles... They explained a fair bit. Also came in handy. http://www.minispares.com/Articles.aspx?ty=ad&aid=127 http://www.minispares.com/Articles.aspx?ty=ad&aid=129 These articles talk about potentially binning the std brake limiting valve (http://www.minispares.com/Product.aspx?ty=pb&pid=37054) and replacing it with the Minispares one (http://www.minispares.com/Product.aspx?ty=ar&pid=38406). What I don't understand though is unlike the std valve which has four ports, the Minispares valve only looks like it has has three ports. Is the Minispares bias valve only for use with a single circuit master cylinder - so that there is one line from the master cyl to the valve; and then one line to rear / one line to front? The ones for tandem brakes we had in Oz have 5 ports;- 2 in from M/C 1 to rear, and 2 for fronts The UK ones (at least the late ones) have only 4 ports, it has one less front one. The Adjustable valve is made up from the early single circuit brakes but will work quite OK with tandem brakes. You could fit this as per early brakes, in the rear subframe. When the system pressure is high enough, this valve will shut off any increase in pressure to the rears. Because the Tandem M/C has a hydrualic coupling between front and rear circuits, the rear outlet will no longer flow fliud via the outlet once lock-off pressure has been reached and so all the fluid will then act on the piston for the front circuit.

Author:	Mearcat [ Fri May 28, 2010 4:52 pm ]
Post subject:
To get things clear GT mowog, are you saying that in arjay's pic above, it could be set up so that '2' regulator can be removed and ensure that '5' is a pressure limiting valve? So with this setup, the '5' valve is adjusted to lock up the front wheels just before the rear. This whole brake set up thing is confusing

Author:	GT mowog [ Fri May 28, 2010 4:58 pm ]
Post subject:
Mearcat wrote: To get things clear GT mowog, are you saying that in arjay's pic above, it could be set up so that '2' regulator can be removed and ensure that '5' is a pressure limiting valve? So with this setup, the '5' valve is adjusted to lock up the front wheels just before the rear. This whole brake set up thing is confusing Yeap, although best if the rears don't lock at all, but that might depend on your driving style Thinking a bit more about, I cannot see why they fitted the FAM7821 pressure regualtor to Oz Minis. They never fitted them to Mokes (and some UK Minis), they used an interal system which was much better as it adjusted the shut off pressure to the rears according to the weight in the rear and the G force of the stop.

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Author:	arjay [ Fri May 28, 2010 7:55 pm ]
Post subject:
okay.. so i accidently lost the original picture, dont ask me why. Although if you happen to have saved the original could you please PM me. so i can re-upload it. I think this will be the eventual setup below. A dual master cylinder attached to the pressure regulator with a brake fail switch, which will have 2 valves in and either 1 or 2 valves out for the front, and 1 more out for the rear, and finally the rear proportining valve. So Alan, i guess i no longer will be using a servo as its probably not the safest route.