Morris Minor Owners Club

Hi, I am trying to remove the front brake cylinders but don't have a socket to fit the small bolt that holds the cylinders in place (as well as a larger 1/2" bolt).

Does anyone know the correct Whitworth or AF size please? It's 8.5mm across the flats.

Did mine recently, cant remember but might have been lucky and had an 8.5mm socket, did take a bit of messing about with at the time.

Not sure but I suspect that's 3/16" BSF which needs an 1/8" Whitworth spanner/socket.

Alex is correct 1/8W socket - 11/32AF is a very close fit though.

Rog

Thanks chaps!

Will get onto my toolshop right away (eBay).

Nick
Swindon

1/8W it is

You won't get that in Hellfrauds! I'm sure I found a little metric socket that was a very good fit.

You won't get that in Hellfrauds! I'm sure I found a little metric socket that was a very good fit.

As mentioned 11/32AF is a good fit which are available through Mangos Sockets (along with many others - spanners too) PM your wants

Rog

Sorry to revive a very old thread but I'm doing this job right now and having terrible trouble with the same small set screw that holds the brake cylinder on.

1/8 Whitworth is suggested as the right size but it is too big and slips. 5/16AF is too small. I do hope 11/32 AF is correct because I have had to order a spanner. If all else fails I am going to have to file down the set screw head until 5/16AF will fit. As usual, what appeared to be a fairly straightforward job turned out to be anything but.

1/8" BSW / 3/16" BSF head size is 0.338" AF, so is slightly smaller than 11/32" (0.3438") by 0.006". An 11/32" AF open ended spanner is more likely to slip than the 'correct' 3/16" BSF.

A 6-point socket of either 3/16" BSF or 11/32" AF would be my first choice, and after that 2BA is smaller at 0.324" AF, so a sturdy 12 point socket could knock on to a worn 3/16" BSF head?

For metric, 8mm is smaller than 2BA and 9mm is larger than 11/32", so would not be the most likely solution.

Thank you for your explanation. So 1/8 BSW is actually smaller than 11/32 AF. This is not good news because I am using a 1/8 BSW socket and it slips. It "feels" like the perfect size but slips as soon as there is any torque. I have tried it on both small set screws because I suspect I have mashed the head of one of them somewhat. 5/16 AF is a very close fit but the spanner is just too small. These set screws are very corroded so perhaps this explains the trouble.

Actually I did try some metric sockets as well. It's somewhere between 8 and 9 mm but I don't have an 8.5 mm socket and I don't know whether they even exist.

Do you have a 2BA socket to try?

No I haven't got any BA sockets or spanners. I'll have to buy one.

If you have to buy a socket make sure you get a 6 point one.

The screw thread is 1/4" UNF - I have seen various different size heads on these screws. May be as well to just drill the heads off if THAT stuck - especially if changing the cylinder anyway! Spot of copper slip when you refit them....

It may come to that. I hope not. I do not know how to dissemble further at this stage and I am away from home a long way from the car at the moment. I would have to get the backplate off the car because I can't drill out the set screws in situ. It is another example of dissimilar metal corrosion. A steel set screw in an alloy cylinder with hygroscopic leaking brake fluid.

Once I managed to get mine out I replaced them with high tensile allen screws. With or without copperslip the heads never deform or round off. I should have some knocking around if needed.....

As long as you fill the head with a blob of grease...

Allen screws do sound a good idea. So how do I get the backplate off? Brake lines are all disconnected and shoes are out.

Remove the hub - just pulls off (after removing the split pin/nut and washer) - if a bit tight refit the wheel and wiggle gently.. Then undo the 4 bolts securing the backplate and PULL!