new brake pipes don't fit

Post by **youngb506** » Mon Sep 29, 2008 8:44 pm

I've had to put a new pipe between one of the flexible brake pipes and the three way connector under the bonnet where the brake switch sits. The trouble is that although the nuts on the end of the new pipe fits the new flexible pipe, the thread is clearly wrong for the old brass three way connector. The old one looks like it has a coarser thread. Whats going on? Mine's a '58 saloon. If the three way connector is orriginal, would it have a different thread to all the new brake components? What do I do? Any help greatly appreciated.

Barry

Post by **bigginger** » Mon Sep 29, 2008 9:26 pm

The threads on the 3 way under the bonnet and the one on the rear axle are different - could the pipes have been confused?

linearaudio · Post by **linearaudio** » Mon Sep 29, 2008 9:40 pm

Just had the same problem on my 1962 traveller. Flexi end is UNF thread, junction end BSF. Don't know if it should be but it was! Fortunately I was well aware that it was getting dark and not a good time to be doing this as I had to collect the girls from Guides in 30 mins, so I didn't try to persuade the wrong threads to mate!!

Post by **youngb506** » Mon Sep 29, 2008 10:10 pm

bigginger wrote:The threads on the 3 way under the bonnet and the one on the rear axle are different - could the pipes have been confused?

I had the pipe made up. Do I need different threads for the flexi end and the three way junction?

linearaudio · Post by **linearaudio** » Mon Sep 29, 2008 10:18 pm

Thats the ticket! The coarser end needs to be BSF thread. Also BOTH ends need to be "op 2" ie double flared, had trouble convincing my maker of that!

Post by **bigginger** » Mon Sep 29, 2008 11:55 pm

LINEARAUDIO wrote:Thats the ticket

I disagree - AFAIR both ends are the same, and somone who remembers will tell you what the thread is soon

Post by **youngb506** » Tue Sep 30, 2008 8:21 am

bigginger wrote:
LINEARAUDIO wrote:Thats the ticket
I disagree - AFAIR both ends are the same, and somone who remembers will tell you what the thread is soon

Having checked, the screw in part from the old brake pipe obviously fits the junction but isn't the right size for the flexi pipe which takes a narrower thread, the same as the new wheel cylinder. Odd?

Post by **bmcecosse** » Tue Sep 30, 2008 12:02 pm

Well - all the connections at the front of the car 'should' be the finer 3/8" UNF thread - only the rear axle connector and the rear wheel cylinders have the 3/8" BSF thread which is coarser. So - if your car is different it must have been modified in the past be someone . Check very carefully - because the different threads will definitely NOT work well together !

linearaudio · Post by **linearaudio** » Tue Sep 30, 2008 5:54 pm

[quote="youngb506 Having checked, the screw in part from the old brake pipe obviously fits the junction but isn't the right size for the flexi pipe which takes a narrower thread, the same as the new wheel cylinder. Odd?[/quote]
Certainly odd, but as I said, whatever you're "meant" to have- you've got two different ends (same as mine) "narrower" thread unf, coarser thread bsf. Get one end re-done with a bsf thread and forget about it!

Post by **Mogwai** » Tue Sep 30, 2008 10:06 pm

from what ive seen all the unions are BSF exept the front wheel cylinders & the male ends of the 3 flexi's are UNF

Post by **bmcecosse** » Tue Sep 30, 2008 10:13 pm

Master cylinder is definitely 3/8 UNF. And originally ALL the car except rear axle connector and rear wheel cylinders were 3/8" UNF. But - who knows whats being going on since it left the works!

Post by **bigginger** » Tue Sep 30, 2008 11:13 pm

We've had this discussion more than once, and pretty recently too. It should be/was originally just as above - on the later cars, at any rate. I'm a dunce over the older ones

Post by **jonathon** » Tue Sep 30, 2008 11:38 pm

The last car we re piped had coarse bsf front 3 way and fine 26tpi unf on the front flexi's. Coarse bsf m/c fittings and at the rear

Post by **bmcecosse** » Tue Sep 30, 2008 11:47 pm

Ehhhhh ??? Even the rear wheel cylinders ???

Post by **jaekl** » Wed Oct 01, 2008 1:25 pm

There can be two types of fiitings on a Moggy, some are 3/8 BSF and some are 3/8 UNF. Not just the threads are different so is the flare. The BSF ones do not have a complete double flare. The metal is not flattened onto itself like the UNF double flares. The BSF ones are convex and the UNF are concave. Look inside the rubber hose fitting to see the receiving part of the flare. It needs to match the flare type. The wrench size is ever so slightly different, BSF being 3/16 Whitworth (bigger) and UNF is 7/16 inch.
I don't know when the change was made but was probably with the formation of BMC but definitely by the Series IIII. At this point the front wheel cyllinders were completely UNF which reguired UNF in the rubber, soft line at the male end only. Sometime later the rear hose was also changed so that they would be the same as the front hose.
That is the situation through the Series III cars. I only have one Series V and I have not worked on it yet. Can someone with certainty identify if any other fittings were changed to UNF.
On a side question do your hardware stores offer similar stocks of metric, UNF, BSF, and Whitworth fasteners or is just metric common?

Post by **alex_holden** » Wed Oct 01, 2008 2:39 pm

jaekl wrote:On a side question do your hardware stores offer similar stocks of metric, UNF, BSF, and Whitworth fasteners or is just metric common?

Imperial fasteners are becoming hard to find locally. You won't find them in a general DIY store. You have to try an engineering supply type place, and then if you're lucky they might have some dusty drawers of old parts hidden away in the back somewhere.

Post by **jaekl** » Wed Oct 01, 2008 2:51 pm

Thanks, I have a thing for nuts and bolts and was wondering what your status was. Here it still is the coarser thread not even UNF in typical DIY stores and metric is individually packaged and expensive. Forty plus years and we (general public) still just have our big toe in the water. I realy don't care which system is used but it make more sense if the whole world used the same.

Post by **bmcecosse** » Wed Oct 01, 2008 6:27 pm

My vote is firmly for UNF and UNC then !

linearaudio · Post by **linearaudio** » Wed Oct 01, 2008 7:06 pm

[quote="jaekl"]Thanks, I have a thing for nuts and bolts and was wondering what your status was.quote]
From what I've seen of your good ole US ofA, you guys can get more nuts/bolts in your local Wal-Mart than we can in any DIY store. Haven't seen a decent Hardware store for donkeys years (creaky floors, dusty corners and old men in brown work coats serving you from behind a counter). Anything other than metric is difficult. On a slight tangent, I had to repair a "bivvy" for a fisher friend of mine recently. 6 months old, made in China, using.... BSCy threads!! So the whole world hasn't quite gone metric.

Post by **autolycus** » Wed Oct 01, 2008 10:20 pm

I wouldn't normally argue with bmcecosse, but I must put the case for BSF/BSW.

In the common car sizes: UN bolt heads are too shallow, the A/F sizes are reasonable for 1/4", but get progressively worse for 5/16 and 3/8, which just looks wrong (too small) and 3/8 UNF is just too fine. And I won't even mention (because I can't be bothered to check which size it is) the one where the nut and bolt are different A/F.

Just hold some BSF bolts, and gaze in wonder at their perfection of form.

Proper bolts, for proper motor cars, have square heads, of course.

There were 9 different thread standards on an MG I once owned (down to 6 after restoration)

Kevin