Adapting a rear axle for Girling brakes

[Charles P]

To fit Girling type rear brakes to an earlier car I'm told that you need to machine down the backplates.
Having done this I've discovered an oddity and I'm after advice.
I turned down the brake backplate mount so that it just cleaned up the boss for the spring mounting pin. This gives an OD of 4.25 whereas a Girling backplate needs 4.00. See the picture. I wouldn't want less metal around the pin. 
Did Austin alter the spring or pin position for Girling brakes or am I unlucky in trying to adapt the "oval backplate" 1935-ish brakes? Or perhaps this is normal and I'm worrying unnecessarily!

   


Thanks 

Charles

[Ruairidh Dunford]

I hope these help you Charles.


   

   

   

[Charles P]

I hope these help you Charles.

Perfect. Thanks R

I'm being more cautious in how much metal I was leaving around the pin. I suppose because it goes in at an angle there is more metal around the inner part of the pin

Charles

[Steve Jones]

I did exactly this three weeks ago, Charles. I didn't think it would work either, but it does. The key is when you realise how little metal there is between the pin hole and the outer edge of the hub flange on a Girling axle as demonstrated by Ruairidh's photos. I'll take a backplate off and photograph what the finished axle end looks like later today.  In my case, the axle had already been modified to take Morris hydraulic backplates so 75% of the work had already been done when that modification was made, probably about 1960.

   

   

   

Steve

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More photos, Charles. Note the 'angle grinder' finish!! Whilst the diameter of the hub flange needs to be a nats under 4", it only needs to be that at it's most outer edge. From there, the outer pin bracket can be formed at an angle leaving a fair amount of metal in place.

   

   

   

Steve

[bob46320]

I don't know if this picture helps.  Unfortunately, I don't have the axle any longer.

[Charles P]

Thanks chaps.
I might achieve the taper by means other than angle grinder (posh eh?) but it'll serve the same purpose.

Charles

[Alan]

Mines been like that for the best part of 40 years, Charles. Been ok so far.

[Charles P]

TGood to know it works.

My rears are actually going hydraulic to match the front.
The fronts have been dogged by twitching to the left under first hard braking (after the first stab they're alright for a while, if frequently used but it doesn't engender confidence). I reckon this is the front cylinder on the right hand side being a bit lazy (seems so under test on axle stands.). It'll be replaced. I also suspect that it's exacerbated by strong brakes at the front only, making the car more nervous. And the diff was leaking through a gasket so I needed to address the axle anyway.

Charles

[Ruairidh Dunford]

If you are fitting MM hydraulic back plates you will also need to make the sides flat or like those pictured in Steve’s photos.

[Charles P]

If you are fitting MM hydraulic back plates you will also need to make the sides flat or like those pictured in Steve’s photos.

Roger that. I already have the backplates and whilst I could put the axle on the milling machine and be "precise" I think that I'll crack out the angle grinder for that job. 
I also have the 50's style handbrake cable fixtures but I'm also considering a rod operated approach, with a pivot bracket on the axle as on the late Rubies. Opinions welcomed.

C