brake pipe/ unions size confusion

[dorsetpickup]

hi - finally progressing now that i understand the tormented set up of clutch and brakes; i now have a functioning clutch, and master cylinder overhauled and in place...

however on coming to the last connection twixt pipes and unions, at the rear flexi to master cyl connection (on a 68 pick up where so far all has been bsf) i seem to have a bsf on the copper pipe as expected, but endeavouring to go into a unf hose... (which goes to a unf union, which in turn the two outlets to the two copper pipes are bsf).

according to my rimmer parts book unf is an option but does not go into any detail... for the life on me this seems unnecessary complicating things, so can anyone tell me why this daft situation came about?

presumably i have to get the master cyl to flexi copper pipe retro fitted with a unf on the other end (the master cyl one is definitley bsf).

am i being thick? or is it no wonder our manufacturing industry lost out when the rest of the planet kept things simple.

[taupe]

Hi

Assuming you have the standard set up-

The rear flexi hose should be standard BSF female to accept the BSF pipe/union from the master cylinder

The other end of the hose is UNF and screws into the 3 way T connector the bottom one of the tee is marked with UNF on the casting The other two ways on the tee are BSF to the rear brake cyls.

Although it seems a bit strange to mix these threads it does result in the front and rear hoses being the same ie one end UNF male, other end BSF Female.

Also all the main brake pipes have BSF both ends except for the two short pipes linking the front cylinders.

[dorsetpickup]

thanks - very interesting! not sure i understand why the design mixes unf and bsf still, but knowing what it is i don't know helps!!

presumably they are oem parts that used unf that had to be fudged to fit our old and rapidly becoming obsolete sizes... i suppose the logic you are saying is that the front bsf pipes went into hoses that went into unf slave cylinders and therefore to keep consistency the rear did the same, albeit that it was a cast 3 way union where strictly it needn't have?

i can only assume that somehow i have an incorrect hose with female unf and male unf... the female end definitley took a unf bleed nipple comfortably (to check the thread type) whereas a bsf was in danger of cross threading, unless that is what has happened pre my ownership, but the thread looks sound enough.

the hose has a various numbers and code and is 'lucas'... i am guessing someone has unwittingly fitted a unf x 2 hose... as the vehicle was unfinished when i bought it, and i guess the error was not noticed.

[taupe]

Yes

It is also possible that some later vehicles had a UNF pipe from the master cylinder to the rear but ive never seen it listed anywhere.

I have a 66 parts list theres only one part No for this pipe (RHD): AJD108

[bmcecosse]

There seems to be quite a bit of confusion over the brake pipes! The front half tends to be UNF and the rear BSF - the rear axle is always BSF., and the front brakes are always UNF - in between - quite a mix!