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MG MGA - MGB pedal box/master cylinders

Hi,

At the risk of being flamed here - has anybody fitted the MGB pedal box/master cylinders to their A.

I'm looking to improve the safety aspect of my A project and would like to separate the brake and clutch master cylinders, as well as (hopefully) fitting a dual circuit system.

I've not looked into this in any detail yet, so I'd like to hear member comments and views.

Chris.
Chris Bond

I have attached a photo of a MGB dual circuit brake master cylinder and separate clutch on a MGA. It is not my car, so I cannot give any details.

Mick


Mick Anderson

Hi Chris,
Yes, I have fitted a 1972 B system to my A. The assembly fits tight but will mount to the existing A location as well as the upright bulkhead for support. One hurdle was creating the lower support, pedal return stops and return spring mounts under the heater shelf. After I did I, looked at a friends Twin Cam and it's remarkably similiar. Check out a Twin Cam setup for reference. I also used the B pedals but had to bend them to clear the steering shaft and space them for my large feet. They ended up a little higher that the A pedal setup but it still works. Search Lyle Jacobson on the net. He has a list of picts to show his setup. He chimes in from time to time too. I used a HTOB and a braided line with the B clutch master cylinder too.
SJS Steinhauer

Chris and Mick
Well I'm blowed!!!!! The image submitted with Mick's words is off my car Twin Cam 1959, Glacier Blue, KJX 157, YD1188. See - I'm proud of it!!! (Image attached)
However, to return to the thread, and to clarify or possibly confuse matters, Bob West told me that the dual circuit brake master cylinder was installed by the PO off a Vauxhall Victor around 1992. I could have this all wrong as I've never thought to question the info or investigate it as the system works so beautifully, aided by a neat servo installed unobtrusively under the dashboard, about 6 inches behind the radio cutout. All very reassuring in action and even feels quite "modern".
Possibly my info on the naster cylinder is duff and it is indeed off an MGB and perhaps someone with eagle eyes for these things could say if they recognise it.
Bruce
B Mayo

Image this time?
B Mayo

Nice to see it can be done and so neatly - just in case the quality tandem replacement set up gets in short supply.
Cam Cunningham

Bruce love the install but one question that begs to be asked. The MGB tandem cylinder used was designed for a disc/drum setup. My advice (from the Aussie Hotrod forum) is that in a didc/disc setup where the converter uses a disc/drum tandem m/cyl there is a small valve on the outlet side of the rear drum brake output that needs to be removed if the m/cyl is being used in a disc/disc setup or else the rear disc brakes will drag. I wonder if yours has had this upgrade? I am also doing a twincam disc conversion with a tandem m/cyl and will investigate further as i near that part of the restoration and advise
regards
mark
Mark Mathiesen

Mark,

Do I understand what you are saying?
Are you saying that in a tandem master cylinder that the front output goes to the front brakes and the rear output goes to the rear brakes?
My experience with Triumph tandem master cylinders is that the primary part of the master cylinder supplies the brakes of all wheels. If a front or rear hose bursts the secondary master cylinder chamber will only then operate.
A sliding shuttle valve cuts off supply to the burst hose.
How does the MGB tandem MC work?

Mick
Mick Anderson

Mick, in the MGB dual circuit brakes, as well as all US cars, the output nearest the cylinder mounting flange goes to the front brakes. The other to the rear. If one end fails there will be an increase in pedal travel but you still will have brakes on one end of the car.
J Heisenfeldt

Mick you have a misunderstanding of how a dual master cylinder operates. J. Heisenfeldt is correct. Looking at the attached drawing of a dual master you can see that between the front brake piston #6 and the rear brake piston #8 there is only a spring #7. Your foot pushes directly on piston #6 forcing brake fluid to the front brakes. Moving piston #6 moves the fluid that surrounds the spring #7 that fluid pushes on piston #8 and it (#8) pushes fluid to the rear brakes. If either half of the system looses fluid or pressure the space in front of the offending piston collapses and the remaining half works with a solid but low pedal.


R J Brown

I thought that typically the dual brake lines were "crossed" so offside front and nearside rear were on one circuit and nearside front and offside rear on the other.

Is this a modern convention?
Dan Smithers

Here's a photo of my MGA with the B master cylinder set up in the building stage. The hard part was getting the wiper motor next to it. Very tight fit. I hope I never have to replace it. I never use the wipers much anyway.

Lyle


Lyle Jacobson

Thanks everyone.

Most informative and helpful, as usual.

Luckily Lyle I wont have the wiper motor problem, but I sure had a steering problem!

Chris.
Chris Bond

Chris, I was specifically referring to the use of the MGB m/cyl in a disc/disc setup such as the twincam or Delux. To quote the Hot Rod Forum guys regarding the use of a tandem disc/drum master cylinder (such as those used in the USA MGB)and fitted in a disc/disc setup such as the twin cam..."Yes you will need to remove the residual pressure valve for disc/disc applications. You first remove the brass seat (small screw in slide hammer is easy!) then remove the small rubber valve, put the seat back in and presto!". Obviously the use of an MGB tandem m/cyl in a stock MGA disc/drum setup will not require this modification
regards
mark
Mark Mathiesen

This thread was discussed between 26/02/2008 and 29/02/2008

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This thread is from the archive. The Live MG MGA BBS is active now.