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MG MGB Technical - Mgb tandam brake master cylinder

Hi all. Can anybody give me the bore dimensions of the MGB tandam master cylinder, non servo and is there a difference with the American version GMC 235.
Thanks for any help.
s page

The non-servo tandem system was only used on North American spec, other markets (UK at least) continued with the single-line system until they got the boosted dual system.

I don't know the bore of the non-servo master but it can't be that different to the single circuit I would have thought, without having an effect on pedal pressure.

Whilst the single-circuit servo was optional and gives little assistance, it's been said that the dual servo gives a lot of assistance making it almost undriveable without. I've not been able to verify that yet but certainly with the engine off the pedal is rock-solid with almost no travel, but with the engine running it can sink noticeably.
paulh4

Early single line cylinder is = 3/4"

68-74 US spec dual line cylinder = GMC235 = 3/4" and will bolt up directly to the single line pedal box

75-on dual line m/cylinder is 13/16" and won't bolt to the early pedal box without modifications--it has a horizontal bolt pattern opposed to the other cylinders having vertical---This cylinder in std form was operated by a pedal driven servo facing out into the engine bay
William Revit

Thanks to all.
s page

This thread was discussed between 23/02/2024 and 24/02/2024

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