Well 9 hours labour charge later....
The brakes are now REALLY good. Smooth, progressive & will just about stand her on her nose! worried about the front shocks now......
Had the shoes relined by someone who knows what he is doing (will pass on the name shortly) I now have spare relined shoes as I had them all done!All new springs, but the beehives were too short & too stiff; one tang even snapped when trying to fit it. So the old ones are back on together with the best snails from my car and the donor front brakes. The 15/16th rear cylinders work fine.
The brakes were refitted, set & road tested, then taken down again to see what it all looked like. The rubbing was even & continuous. Brakes reassembled reset & readjusted, road tested & readjusted. I took the car to work today (30 miles each way along A roads & M42/M6. Several heavy braking from 70plus...straight & steady. What a difference. I will check the rod length over the w/end as I had seriously altered it to get a better pedal feel last year.
Now I MUST try & find the source of the many buzzing noises. Bonnet is one for sure, as is the box under the dash for the so called heater....

I will replace the springs & beehives - although I bet they are of doubtful modern re-production! Perhaps I should replace the rear cylinders with 7/8" after all...all this talk about the 15/16" putting less pressure on the brakes is not what I want...now if I were putting discs on the front, well maybe. I think I have some Manumatic service information somewhere...are there any out there I wonder? Incidentally one rear shoe was different to the others! No slot between the two wide spaced holes, but where the foot of this shoe (the end without the semi circular cut out) met the "fixed" pivot, it was really noticeably worn away! It was the bottom shoe - also delaminating & covered in oil!! Perfect.

Hi David

The two main problems with the brake shoes skewing are the springs on the shoes are incorrectly fitted or the beehive retention springs are left off or not located properly.

The Manumatic master cylinder is identical to the manual master cylinder the only differences are the clutch bore needs to be opened out and then honed to size and the hydraulic outlet threads need to be drilled and tapped.
These cylinders are really cheap to buy as there is no call for them, I purchased 2 for £15 last year, and it cost me £100 to get them machined, a real find, seen a few on ebay and at autojumbles
The trouble with making changes to the rear bias is the rear brakes are normally lightly loaded and will lock up quicker or not work at all, you could run out of of brake fluid in the worst case before the bakes work, depending whether the slave is larger or smaller, in your case it will be larger so the pedal will need to travel further to get the braking effect.
You probably know all this.
Best Trevor

latest update! A full set of front brakes are on the way to me. They apparently worked very well (changed for discs) so that will give me a "control" set.
As for the rears I am changing the cylinders & will fit a pair of 15/16" that I happen to have! A little extra power on the rear won't be a problem I think.
For information I have checked my 1958 Lockheed book & MGA & ZA/ZB hoses are NOT interchangeable. Not only are the Z hoses 14.5" against 12.5", but the internal thread is 3/8 20 BSF on the Z as opposed to 3/8 24 UNF on the A. The external thread that takes the locknut is 5/8 26 BSW on both and the thread into the wheel cylinder is 3/8 24 UNF. ..There will be a short test paper on this later!
As a complete aside, the Master Cylinder on the Manumatic (any left?) is different to the Manual cars. Part numbers 89515(MM) as opposed to 35753(M)

well the drums looked like new after a light polish. no need to skim. they are 10 inch i/d. Good news. We also measured the shoes. Guess what...they came out as a perfect 10" diameter as well! The drum rubbing surface is perfectly flat and "square" so why was the lining only wearing/rubbing on the outer edges?
David

After a flurry of correspondence on the "other" site I think it may be interesting to hear my saga!
I had pretty dead pedal, but the car stopped OK-ish ...didn't cause problems with stopping on the trip to Bavaria last year, but I was not happy with them.
In the time I have had the car (Oct 2010) I replaced the front cylinders and the front shoes (mid/end 2011), The rears were just cleaned out & a paper seal replaced on the half shaft.
Fast forward to now & the rears were found to be almost useless! The n/s cylinder was seized & not working at all & the lower shoe beginning to come away from the lining! Top shoe ok. On the o/s it looks as if the linings were only working on about 1/4 of their area! This was not evident before the trip to Bavaria...so some hard pushing had brought this to pass. I think the only reason that the car didn't pull to one side was that both sides were equally useless! The handbrake worked well.
though! I had thought that the o/s/r drum might have been oval. Both rear cylinders moved freely in the slot in the back-plate.
So two new rear cylinders on order.
I think I will replace all the shoes/linings as the front ones are also unevenly worn. N/s good, o/s patchy! What linings does the world of ZA recommend? And from whom? My fronts came from MG Services.
I am taking the drums & some linings to work to get them measured just to see how round etc they are (we have a magic machine that measures things by looking at them!
I will report back!
David