Brake pipe union threads

[southerly95]

ESM list a UNF and a BSF brake pipe union/nut. Does anyone know which thread is used for which application please? Many thanks, John

[bigginger]

3/8 UNF front and 3/8 BSF rear. Funny old world...

[Dominic]

Hi John
It's just the bridging pipes between front cylinders that have the UNF threads. All the others use BSF.
I have just found a good firm that supplies ready made kits, they also supply kunifer sets at only £26. Their website is www.stevsonmotors.co.uk
I have no interest other than as a satisfied customer!
Dom.

[bmcecosse]

NO - it's NOT! The 3/8" BSF 'coarse' threads are on the rear axle only - ALL other threads on the Minor braking system are 3/8" UNF.

[bigginger]

Agreed - for confirmation.

[MoggyTech]

Seconded, motion carried.

[Dominic]

I'm just going by a) what I found in the brake pipe kit, which matched b) what was already on the car which was confirmed by c) the MGM spares website info box on the relevant items (though admittedly they say that 16 of the coarse threaded unions are required as well as the 4 finer threads.

[bigginger]

..and I'm just going by having done the job many times and what the workshop manual says ;)

[bmcecosse]

And I'm going by what is actually on these cars - and has been so for 60 years now! They have it wrong - send it back.

[Dominic]

Maybe I'm confused by the thread names? I have just double checked: the finer thread is only on the front brake cylinders. to which the bridging or link pipe, front bleed nipples and flexi hoses fit to. There is a fine thread in the centre of the rear T-piece, to which the rear flexi hose screws into. All the other fitments have a slightly coarser thread. This is what was actually on my car, and which the new brake kit actually fits without problems.

[jaekl]

I'm going to add my two cents. On the Series III cars everthing is BSF except all of the ports of the front wheel cylinders which are UNF. The rear brake hose was BSF into the brass junction on the axle (very early Series III but later was changed to UNF to match the front. They may have changed the tubing fittings later on, but what about the banjos? Did they stay BSF?
The rule I go by is if it is original Morris it's BSF and if it is Austin, it's UNF with the exceptions of the front wheel cylinders and the front spring bolt.

[bmcecosse]

As said above - early cars may have more BSF, - but certainly 948 and 1098 cars have UNF (fine) thread on front wheel cylinders, front flexis, X piece with brake switch, master cylinder and centre port of the rear axle T - that leaves BSF (coarse) thread on the two arm ports of the rear axle T and into the rear wheel cylinder banjos.

[Dean]

No wonder we went to metric! Metric fine or metric coarse which will it be sir!

[bmcecosse]

Sadly even then we couldn't get it right - the later Mini for example has a mixture of 3/8UNF and M10x1 fittings !! Dangerous thing is - the will 'just about' screw together - and some have done just that, only to have the joint fall apart with disasterous results.

[craman]

Hi guys,

The last post was 8 years ago and going to re-build my 1957 948cc soon.

Going by the common consensus here, it's UNF for the front and BSF at the rear, that's just about right. Looking at all the major suppliers, only MOSS lists the sizes of their pipes. It seems that all are BSF, except the front Flexi is not stated while others on eBay and BM sell their Flexis 3 per set, am assuming they all should be UNF as the rear 3-way center is UNF going from what has been said here.

My question is, from the M/C bolt banjo to the rear would be, BNF at one end of the pipe and UNF at the other end which connects to the Flexi? and the same would go for the banjo adaptor at the M/C which goes to the 4-way front, BSF at one end of the pipe and UNF at the other?

Am I correct to assume this?

Chris

[bmcecosse]

Yes.

[craman]

Thanks bmcecosse.

So essentially, there are only 2 brake pipes with BNF and UNF ends in the braking system.

Regards,
Chris

[bmcecosse]

BSF..

[craman]

Yes, BSF...

[taupe]

Well........I think you are wrong...and all the specialist suppliers and the below moprod diagram are correct..

Ive posted this before but here is the Moprod catalogue for the minor 57-71 models - its all 3/8" bsf ref SPN on the diagram except the front brake cylinder link pipes 'D' ref SPA on the diagram which are 3/8" unf.

The only thing you need to check is are your fittings double or single flare as there is some variation in this (or perhaps non standard fittings may have been fitted).

The numbers after are the overall length in inches eg SPN 52 = 3/8" bsf both ends, 52" overall pipe length.

[/quote]

The rear Flexi hose threads are also 3/8 UNF into the rear tee but all the outgoing pipe unions are BSF