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Dual Circuit Brake Conversion


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#1 Pete649

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Posted 09 August 2018 - 04:51 PM

I have a Rover Mini 1000 City X rebuilt as a track day car (with a Yamaha R1 engine in). The car was built in 2014 by a well known mini builder but it only has a single circuit brake system. I have declared this to my insurance company and there was no comment from them, they still offered to insure the vehicle. Not totally sure on the legality of having a single circuit braking system in a later mini though. The car does have a brake proportioning valve fitted so maybe this is why it was converted. Has anyone ever converted a single circuit to a dual circuit braking system? Do I need to do this? Any advice would be appreciated.



#2 harrythehat

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Posted 09 August 2018 - 05:08 PM

not sure on legal side or if there is a legal side except MOT requirements as long as its made there percentages then fine

would be safer with a dual circuit IF! a seal failed tis all.

not sure if theres a different fluid or braking capacity between the two cylinders, shouldn't be hard to find out

would I bother doubt it



#3 unburntfuelinthemorning

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Posted 09 August 2018 - 08:18 PM

I think the MOT minimum handbrake efficiency requirement is only 16% for cars with dual circuit braking systems but 25% for cars with single circuit systems - shouldn't be a problem for a well serviced Mini handbrake.  Not sure about the legality of the conversion though - I think it is alright but cannot say with any certainty.  Definately good that you told the insurance company though.  Hopefully someone else can give you more certainty.



#4 absx2

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Posted 09 August 2018 - 08:21 PM

Minis fitted with dual circuit brakes have a brake limiter valve FAM7821 on the bulkhead.

In the event of a sudden loss of fluid in theory the limiter valve will shut off the damaged circuit giving you front of rear brakes depending on which one popped a seal.

If you are really unlucky some cars were diagonally split giving one front and one rear brake, pretty lethal. At least you know where you are with a handbrake. 

 

Anyway I say in theory as the damn things play up due to lack of fluid changes and old age and can cause more trouble than they are worth. classic signs are the car weaving under moderate to heavy braking and the brake pedal sticking or needing a couple of pumps sometimes.

As the car is very modified my personal take on it is the guy knew his way around minis enough to avoid the problematic valve and fit the tried and tested proportioning valve ( adjustable I hope )

You have done your bit by informing the insurance company so go on and enjoy it.

Short of tearing a pipe off or diabolical lack of maintenance you will never need it, if it worked anyway and as for it being non standard ITS GOT AN R1 MOTOR.

 

Just my personal opinion, I would be well happy with it as it is.



#5 Ethel

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Posted 09 August 2018 - 10:15 PM

Dual circuits became a construction and use requirement in '76. If the car's registered after that date then it should really have them. Does it have a post '76 pedal box - better if you convert back. The FAM valve won't seal off the front circuit, but it won't limit the rear brakes either if the fronts lose pressure.



#6 Retroman

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Posted 09 August 2018 - 11:37 PM

If you do go to a  'split'  system I would suggest a proper bias pedalbox...

 

Separate master cylinders for the front and rear and a balance bar

 

Otherwise its not worth doing.

 

Don't even consider fitting a FAMWTF valve they are a waste of metal

 

The only test for them is to see how far back you can stand an still get it in the scrap skip.



#7 grizzler73

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Posted 10 August 2018 - 06:20 AM

I have the KAD bias set up, nice bit of kit and it requires no body mods.

#8 Retroman

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Posted 10 August 2018 - 10:02 AM

Was gunna suggest the KAD set up,

 

https://kentautodeve...-bias-pedal-box

 

Not a bad price considering



#9 whistler

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Posted 10 August 2018 - 10:12 AM

I have a Rover Mini 1000 City X rebuilt as a track day car (with a Yamaha R1 engine in). The car was built in 2014 by a well known mini builder but it only has a single circuit brake system. I have declared this to my insurance company and there was no comment from them, they still offered to insure the vehicle. Not totally sure on the legality of having a single circuit braking system in a later mini though. The car does have a brake proportioning valve fitted so maybe this is why it was converted. Has anyone ever converted a single circuit to a dual circuit braking system? Do I need to do this? Any advice would be appreciated.

Does the car have a remote brake servo? If so then you'll run into problems when converting to dual circuit system.

#10 Retroman

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Posted 10 August 2018 - 10:21 AM

Just bin the servo



#11 nicklouse

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Posted 10 August 2018 - 10:53 AM

to be honest I would ne expect it to have one.



#12 Pete649

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Posted 10 August 2018 - 02:54 PM

Thanks for all of the replies.

 

To answer some points raised,

 

The car was first registered in 1990.

 

There is no servo fitted.

 

I am not sure which pedal box is fitted but I have added in some photos of the engine bay, although there are air filters fitted now.

 

There is not much space to fit the KAD adjustable bias pedal box although using the AP cylinders would mean the reservoirs could be fitted out of the way.

 

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#13 dotmatrix

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Posted 10 August 2018 - 07:38 PM

Nice looking car. The metro had dual circuit with both circuits going to both front wheels. This means two boosters if retrofitted after the master cylinder and one booster if fitted underneath the master cylinder. Both configurations Work well.

#14 Retroman

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Posted 11 August 2018 - 12:56 PM

Smart looking motor

 

I would be leaving the brakes as they are, you have the simplest and most reliable system which is difficult to improve on.

 

The legality is you have notified the insurance and it is presumably MOT'ed



#15 Pete649

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Posted 11 August 2018 - 04:41 PM

It doesn't have an MOT at the moment but has had one with the current brake setup. 

 

I could always drop in a later GMC 227 master cylinder which should fit space-wise and then connect up the fronts to one side and rears to the other side, routing the rears through the separate proportioning valve (as they are now). Should be relatively straightforward.

 

Then again, I might leave it.


Edited by Pete649, 11 August 2018 - 04:45 PM.





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