Thread: Series 1 brake plumbing

I think you are correct about the thread types and his machine would have had BSF flare nuts.

Unless he is determined on authenticity a UNF union can be used with the appropriate flare nuts,

Cheers Charlie

The brakes were the first thing I sorted on my 1956 86 inch. The threads are BSF, and mine uses 10 inch, single cylinder drums all around, which I think is also different to a S2. The 88's did first appear in 1956 so you are quite right - your friend has one of the first.

Having said that, I'm sure you could use a bit of a mix, unless, as Charles also points out, your friend is a rivet counter.

Authenticity is one thing and practicality is another one. Most likely his BSF flare nuts are getting rounded by now and 3/16 BSF cylinders even more difficult to find.

Depending upon the condition of his entire brake system and what sort of restoration he is undertaking the pragmatic thing to do may well be to retrofit the entire system to the later 3/16 UNF fittings.

BTW the 88" used the same 10" brakes right through to (and including) SIII so shoes, backing plates, snail cams and to an extent drums are interchangeable with the S1 types. The only differences are the BSF/UNF threads we've discussed and the 16mm holes for the SIII wheel studs instead of the 9/16 BSF of the earlier models. You can even retrofit the 2 bolt SIIa CB master cylinder onto the 3 bolt S1 CB master cylinder by drilling a hole in the chassis outrigger. The kits inside are the same.

Originally Posted by Lotz-A-Landies

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BTW the 88" used the same 10" brakes right through to (and including) SIII so shoes, backing plates, snail cams and to an extent drums are interchangeable with the S1 types. .

Exactly Diana.

I used a pair if S1 backing plates on a S11 to fix a problem of flogged holes for the snail cams.