S3 rear brake cylinders

[mentall]

Here I am again after 18 months of lurking: thanks for the endless stream of useful and essential information.
One of the problems on the 'warning to prospective buyers' car was, of course, that the Saab servo was rotted out (no brakes, over-fuelling). I've now fitted a combination of Ka parts to get the 22.2mm cylinder / 8 inch servo required. I won't brag that it works until I can test it, which I can't because the rear wheel cylinders are rusted up.
Now here's the thing: the Lucas 64677523 / Delphi LW37523 reference that you kindly give shows a cylinder with a bore of 20.6mm and pistons with domed shiny ends, and I've seen the thing at my local factors. But my car has 19mm pistons that are slotted to receive the shoes.

What's going on?
And I promise not to lurk any more!

[LawrieS]

I can't offer any guidance but on mine they look like this.

As you can see I have a leak so will be sourcing a new pair too.

[mk1fan]

There really shouldn't be any problems getting the right parts as the drum brakes are a complete 'unit' taken from the Ford range. Don't rule out that someone may have swapped out the cylinders for other items that may have been 'to hand'.

[phillpot]

Personally I'd forget all about part numbers and just ask for a Sierra 2.0 rear wheel cylinder...

[magpies]

standard ford 9" drums as fitted to sporty Mk1 +2 Escorts 2.8 and 3 ltr Capris and Sierras etc

[mep12345]

As above two have said, and they are dirt cheap,


Didn't need to post just wanted to bring up the time on the thread and say from Singapore where it is 31 degrees

[mentall]

Thanks, guys. Here's my shoe and piston:



The piston doesn't look like yours, or the one in my Haynes Sierra V6 book. However, the shoe does look the same, so I'll buy the LW37523 cylinders, fit them, and see what happens.

Stewart, I think you may be right. Or maybe it's the old 'TVR threw on anything they could find' syndrome.
And last year GadgeS3C said he thought the pistons should be 19mm diameter. His car's a 1991 (mine's 1990)

Still a little concerned about the bore size, though: 19 to 20.6 bore is an 8.4% increase in diameter, 17.5% increase in area: a big change in rear:front braking effort.

[phillpot]

mentall said:

Or maybe it's the old 'TVR threw on anything they could find' syndrome.

Or "anybody" over the last 20 or so years?

mentall said:

a big change in rear:front braking effort.

Negligible compared to people fitting rear disc's, bigger front disc's etc...... it'll be fine (imho)

[magpies]

possibly no real change in front /rear as pressure is limited by the big valve on the baulkhead.