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Dual Circuit Brake Conversion


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#16 Moke Spider

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Posted 11 August 2018 - 06:49 PM

I don't know your local laws in the UK, however, I'll just pass on something that maybe worth looking in to.

 

In these parts, you can notify the Insurers of just about any modification and it will just be a notation on the paperwork. They'll happily talk you money and you think you are insured, however if later when making a claim, they find the modification non-compliant (or put another way, illegal) they will knock back the claim as they say it's up to the owner to ensure that the vehicle is legal when being driven.



#17 Homersimpson

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Posted 11 August 2018 - 07:16 PM

Personally for what it is I would change the master cylinder to a dual circuit one, its a small cost but if you are unlucky to suffer a major leak it will be very worthwhile.

 

About 15 year ago I nearly stuffed a 1966 3.8 S-Type Jag into a mercedes at 50mph when the brakes failed, fortunatly the handbrake slowed me down and the merc moved!

 

I also lost brakes on 1964 Traveller that I was looking to buy, fortunatly I was only driving around an offroad industrial estate at 20MPH and was able to put it in a ditch to stop.  I still bought the car!


Edited by Homersimpson, 11 August 2018 - 07:18 PM.


#18 Pete649

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Posted 12 August 2018 - 03:15 PM

OK, I will swap the master cylinder to a dual circuit GMC227 (hope it fits) and make sure there is either a MS72 adjustable proportioning valve in the rear circuit or fit one. Job done. 

 

Hmm, that other thread with a similar title came in handy :-)



#19 Pete649

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Posted 20 August 2018 - 06:46 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.

 

Just had a thought. Since the car probably had a servo in the first place (1990 Mini City X) can I legally remove the servo, i.e. not fit one back on as it does not have one now, without falling foul of the C&U regs if converting back to dual circuit brakes by fitting a GMC 227 master cylinder? I don't know if servos are a C&U requirement like dual circuits are.



#20 Ethel

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Posted 20 August 2018 - 09:53 PM

I think so, the IVA test manual would be a suitable authority to say what'd be road legal. There'd still be the issue that it's not original spec for insurance purposes, but it looks you've already got plenty of other "not original equipment" bits to put you in a part of the insurance market where it won't make much difference, as long as it's declared.

 

The shape of the pedal rubbers are a decent indicator of the type of pedal box.

 

single circuit

 

dual circuit



#21 Pete649

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Posted 21 August 2018 - 04:56 PM


The shape of the pedal rubbers are a decent indicator of the type of pedal box.

 

Thanks for that.

 

Looks like I may have a mixture of pedals, although the brake pedal is cranked up away from the floor a fair bit. I can't really have a closer look at the moment as the car is in someone else's garage.

 

I take it that apart from the pedals themselves (especially the cranked angle of the brake pedal) the tops of the single and dual circuit pedal boxes are different? I thought it may just have been a matter of changing over the master cylinder.

 

Attached File  __376610_orig.jpg   60.79K   1 downloads



#22 Ethel

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Posted 21 August 2018 - 10:09 PM

The dual circuit one has a forked  bit that is clamped by the steering column bracket. The earlier type is shorter and fixed with a couple of bolts through the parcel shelf.



#23 Pete649

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Posted 25 August 2018 - 06:40 PM

Managed to get round to the garage where the car currently is. I have attached some photos of the pedal box. Is this the later 'dual circuit' one?

 

I may have the wrong steering column bracket though as this one does not appear to clamp the forked section unless it is just one side of the fork that is clamped.

 

So, should I be able to fit the GMC227 to this pedal box?

 

Many thanks.

 

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Edited by Pete649, 25 August 2018 - 07:14 PM.


#24 Ethel

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Posted 27 August 2018 - 10:06 AM

I'd say so. There's still the odd square pedal to figure out, suppose it could even be one like the clutch that's been cut down, but can't think why you'd do that - looks like the accelerator's also been tinkered with though. All the bits are interchangeable, but it's the pedal box that does most to set what leverage rate you'll get by setting the distance between the cylinder pushrod and the pedal axle.



#25 Pete649

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Posted 27 August 2018 - 11:34 AM

Many thanks for the reply. I will take a second look at the overall shape of the upper part of the brake pedal to determine which one has been fitted. 






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