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Remote twin circuit Brake Servo Advice
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TonyBrooks



Joined: 02 Jan 2008
Posts: 110
Location: Maidenhead

PostPosted: Sun Dec 21, 2008 2:27 pm    Post subject: Remote twin circuit Brake Servo Advice Reply with quote

I would appreciate your advice on sourcing and fitting a reasonably priced remote brake cylinder for a twin circuit brake system.

As background, I have recently changed the mechanical rod system on my Tornado Typhoon (based on the E93A) to hydraulic. The brake master cylinder was NOS from a Ford Transit (part no Lockheed 4224-729 PT 3P 32D) this is a twin circuit system and I have one outlet feeding the front brakes, with the other going to the rear. The front wheel cylinders were changed to those from a VW bus (part no 131-611 057 from GSF). I retained the single leading shoe system I only had to modify the brake shoes slightly by welding on a small extension plate. At the rear I used a BMW clutch slave cylinder (part no 21-52-1-116-300 from GSF) to activate the rear mechanical rod system. This is mounted on a bracket bolted to the rear diff assembly and this has allowed me to keep the handbrake system without modification. I have used braided hoses throughout obtained from Think Automotive. As far as I can see all the bore sizes are in relation to each other.

To my surprise the system works quite well with the wheels locking evenly on a damp surface but requires a very hard push on the brake pedal. Rest assured that the mounting of the brake master cylinder has been well reinforced! Further research has shown that I have overlooked the mechanical pedal ration as described here :- http://www.mpbrakes.com/uploads/documents/pedalratiopdf.pdf
Sadly, my figures work out to be at best 3:1.

Unfortunately, I am unable to alter the positioning of either the pedal or the brake master cylinder.

So I am considering installing a brake servo.

Any suggestions?
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Nic Jarman



Joined: 05 Oct 2008
Posts: 1035
Location: Stoke by Clare, Suffolk

PostPosted: Sun Dec 21, 2008 4:28 pm    Post subject: Reply with quote

MGBs often have remote servos. I think they are available from places like Behive or mg owners club.
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TonyBrooks



Joined: 02 Jan 2008
Posts: 110
Location: Maidenhead

PostPosted: Sun Dec 21, 2008 6:04 pm    Post subject: Reply with quote

Thanks Nic but the ones that seem to be for sale are for single circuit master cylinders whereas I have a dual circuit m/c.
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Rick
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Joined: 27 Apr 2005
Posts: 21134
Location: North-west UK

PostPosted: Sun Dec 21, 2008 6:09 pm    Post subject: Reply with quote

Don't some Volvos, like the 140 range, have dual circuit (servo) brakes? Late Amazons may have them too, mounted I think on the n/s inner wing.

Rick
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Jim.Walker



Joined: 27 Dec 2008
Posts: 1233
Location: Chesterfield

PostPosted: Fri Jan 02, 2009 2:42 pm    Post subject: Reply with quote

Twin circuit remote servos have been used, but possibly not still manufactured. I sourced a new one at Newark autojumble last year for a friend.
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Phil - Nottingham



Joined: 01 Jan 2008
Posts: 1254
Location: Nottingham

PostPosted: Fri Jan 02, 2009 6:21 pm    Post subject: Reply with quote

Try these?

http://stores.ebay.co.uk/MG-Services-Heathrow_W0QQssPageNameZstrkQ3amefsQ3amesstQQtZkm
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TonyBrooks



Joined: 02 Jan 2008
Posts: 110
Location: Maidenhead

PostPosted: Sat Jan 03, 2009 11:10 am    Post subject: Reply with quote

Thanks for that link - I had already looked at them but their stock seems only to cater for single line brakes. I have a tandem set up (2 lines from the servo feeding seperatly the front and rear brakes) so one of their servos would only work on, say, the front. I have plan B at the moment which is to use a servo and master cylinder from a Saab 96 V4 at it looks like it will fit.
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clan chieftain



Joined: 05 Apr 2008
Posts: 2042
Location: Motherwell

PostPosted: Sun Jan 11, 2009 7:12 pm    Post subject: Reply with quote

I have a dual circuit one here complete with servo and pedals off a Morris Ital if its any good to you.
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SV8Predator



Joined: 24 Aug 2008
Posts: 133
Location: Further up the creek

PostPosted: Sun Jan 11, 2009 8:38 pm    Post subject: Reply with quote

71marina wrote:
I have a dual circuit one here complete with servo and pedals off a Morris Ital if its any good to you.


I think TonyBrooks is looking for a remote dual circuit servo, and that rules out the Morris Ital (and most other cars with dual circuit brakes).
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clan chieftain



Joined: 05 Apr 2008
Posts: 2042
Location: Motherwell

PostPosted: Tue Jan 13, 2009 12:01 am    Post subject: Reply with quote

Embarassed
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Greeney in France



Joined: 06 Mar 2008
Posts: 1173
Location: Limousin area of France

PostPosted: Thu Jan 29, 2009 6:28 pm    Post subject: Reply with quote

In the Classic and sportscar, (one of my subscribed mags to France) I found a company making twin remote break servos;
Stafford vehicle components 08456 581251 290 inc p&p
www.s-v-c.co.uk
1:1.9 assistance ratio
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TonyBrooks



Joined: 02 Jan 2008
Posts: 110
Location: Maidenhead

PostPosted: Fri Jan 30, 2009 11:08 am    Post subject: Reply with quote

Well I am now about to start my 4th go at getting these brakes right! I tried a Saab 96 in line servo/master cylinder set up - soft pedal with no resistance. Kept the same servo and tried my original master cylinder - same result. As I had a servo & master cylinder set up (known to be good) from a Citroen AX gti in the garage, tried that - same result. Back to the drawing board and after research found that all these m/c have a 19mm bore so have now ordered a new m/c with a 15mm bore albeit with single outlet (my wheel cylinders have a 22mm bore). If this works then I shall look at a single remote servo - MG Services Heathrow looks the cheapest and is quite local. In the meantime my garage floor and driveway has been liberally soaked in brake fluid! So far not much expense but many hours making and fitting one off brackets.
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TonyBrooks



Joined: 02 Jan 2008
Posts: 110
Location: Maidenhead

PostPosted: Fri Feb 06, 2009 4:55 pm    Post subject: Reply with quote

I could do with some advice here. I now have the following set up. Master cylinder (5/8ths or 0.6250" or 15.875 mm) vw wheel cylinders 22mm. I have a very soft pedal although I do have braking. There is defintily no air in the system! I have tried isolating each section of the braking system. With just one wheel connected I have very good pressure - with all wheels connceted it goes soft. Suggestions welcome please.
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Penman



Joined: 23 Nov 2007
Posts: 4152
Location: Lancashire

PostPosted: Fri Feb 06, 2009 9:09 pm    Post subject: Reply with quote

Hi
Not certain about the maths, but I wonder if the wheel cylinder diameter/mastercylinder diameter relationship is OK.

Check the required travel for the wheel cylinders and call it L2

The amount of fluid needed is then Volume V = 11squared x pi x L2 x 4

Then look at the equation for the master cylinder. Travel required call it L1.

15.875/2 squared x pi x L1 = V

I wonder if this is going to give you a longer travel than is available in your master cylinder.

Any mathematicians amongst us feel free to correct me if I have this wrong.
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