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MG MGB Technical - Dual master cylinder to brake pipe coupling


Does anyone know where I can get a brake pipe to master cylinder coupling for a non servo dual master cylinder (US type) in the UK?

I'm after the front straight insert that sits between the 3/8 brake pipe coupling and the master cylinder (it looks like it will have a 5/8 UNF thread on the outside). It also holds the small trap valve and spring in position (one of these will come in handy to).

Any help would be most welcome.

M Blacher

The later UK spec 1500 midget used a similar m/c to the US dual-circuit system, so that might be one line of enquiry
Dave O'Neill2

27H 8456, but it does seem to be NLS.
PaulH Solihull

Yes, definitely the same as the Midget, so it may be possible to obtain a pre-owned item as they are NLS.
Dave O'Neill2

The part is called a reducer as it allows a smaller threaded part to be screwed into another part having a larger thread. The early US twin reservoir systems seem to have used two of these, one on the master cylinder and one on the four way fitting. I suspect the master cylinder has some form of larger plumbing fitting and the reducer takes the hole down to the size for the hard pipe's fitting. The fact it is no longer available from the various suppliers does not mean it is no longer available from other sources. If you can determine the thread sizes, it might be possible to find the part from an aircraft supplier or other source. If not, there should be some available on the used part market. If not, I have some friends who own an MG wrecking yard complete with a number of spare master cylinders which should have the part attached to them. Post if you want me to check into availability and price.

Les Bengtson

Merlin Motor Sport do a range of reducers-some of which are imperial
Michael Beswick

Many thanks to everyone that replied and for the offers of assistance.

I'll see if I can find a scrap yard with a second hand Midget cylinder that I can raid. Failing that, it's a job for some hex brass rod and a friend's lathe (me and a lathe is always a combination that's best avoided).

One last question - does anyone have any experience of running the cylinders without the Trap Valves? Specifically, is air ingress from the wheel cylinders really that much of a problem?
M Blacher

M Blacher,

I suspect I have this reducer & the little piece behind it in my parts bin from master cylinders I have taken apart. If you do not find one locally and do not want to try and machine one, let me know and i'll drop it in the mail for you. I would not think it would cost much to send!! Another possibility would be to contact Moss and see if they could tell you where they source their master cylinders. May be you could purchase the part directly from them (if they provide you with the info). May be too much effort for them to provide that detail?!?!

Let me know if I can help you.

Fred Wright

This thread was discussed between 28/11/2011 and 30/11/2011

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