Brake master cylinder research

["Lawson, Dave" <dlawson@service.ball.com>]

Reviewing the archives, the following information was presented for
4000/5000 master cylinders

>>
 
 '79-'83 non-turbo-----22mm bore----431-611-019G
 '80-'81 turbo-----------23mm bore----437-611-019A
 '82-'83 turbo-----------22mm bore----437-611-019B
 '84-'88 all---------------23mm bore-----443-611-021

Naturally there's a disclaimer to this...there's another option for some
'86-88 wagons only...447-611-021 with the 25mm bore....that would cover
the
rare larger rear caliper optioned wagons.


Part no.  v              Year    v               mm      v

431 611 019 K      '78-'81 5000..................22.2mm

437 611 019 A      '80-'81 5000 turbo.........23.81mm.

437 611 019 B      '82-'83 5000 turbo.........22.2mm.

813 611 019        8/ '80-'84 4000 (coupe 81-84)..........20.64mm.

443 611 021       quattro 8/82-85; 5k '84-'88; 5kq '87-'88; 5kt '84-'88;
                          5ktq 86-88....................23.81mm.

>>

I was looking over a few microfiches and found the following data

Early ur-q  23.81mm x 19/17
Late ur-q   25.4mm x 18/18

And for the RS2  25.40mm x 13/22.5

The 200 had similar listings, but I didn't write those down.

We know the diameter of the master cylinder is the first number, but
what I was wondering is what the 19/17 means?
Is it some kind of stroke length for the front and rear parts of the
tandem master cylinder setup?

thanks
-
Dave Lawson