Brakes Squealing: Drums

[Pug_XUD_KeenAmateur]

I must be missing something , so a quick question here, having resolved the issue, to maybe answer my little 'mystery'

My rear brakes (Drums on my 405) were squealing and, having the opportunity of a replacement set of Shoes & Drums; well, it would've been silly not to, specially as I had to have the rear wheels off for some minor and unassociated works

So, after a bit of a faff [quite a lot of a faff actually - them damn adjusters!], I've sorted it with new Drums; silence! But why were they squealin' in the first place? Pic of 'old' drums attached. 'Original' shoes retained.

A bit of detail
function of the brakes was pretty damn good, still is
usually squealing, hot cold, or indifferent
they had a good 'work out' a few weeks back, after MOT work to the load sensing valve, I took it on a long country run with some concrete in the boot and repeatedly hit the brakes really hard - making sure no'one was behind me.

What d'ya reckon?

..and on a different note, has anyone near me got a Torque Wrench I can compare my new 'un with, which I'm not at all confident is accurate

[Hell Razor5543]

Erm, as your location is empty it would be difficult for anybody to know if they are near to you.

[Gibbo2286]

A good clean up of the drums together with taking the shine off the linings would probably have fixed it.

The squeal is caused by the same method as putting a leaf between your thumbs and blowing through them or like a bow on a violin string.....................good vibrations.

[white exec]

As said, usually caused by 'polished' linings and drum surface.
One cure (can work) is to chamfer the ends of the linings, rather than have them end 'vertically' - taking back by 6mm will do.
Also a light coating of thick copper grease (Copper Ease or similar) where the shoes slot into the adjusters and pistons, and where they rest against any 'steady post'. This acoustically couples the lightweight shoes to the heavier brake assembly, and make it more difficult for them to vibrate at high frequency (= squeal).
New shoes, as you've found, will often sort the problem, by changing the friction.