Alfa adjustable calipers

["Graham Hilder" <graham.hilder@domain.elided>]

Greetings Alfisti,

I'm just repairing an Alfasud front caliper which has a leaky piston-seal. =
Now the Alfasud front caliper is much the same as the Alfetta rear, with =
its pesky handbrake and pad-adjusters mechanisms. I was just browsing =
around some Alfetta rear caliper sites on the net, and I came across =
Shiv's site which had a lot of rebuild info from Shiv and others, =
especially Paul, and amongst it I noticed that comment "The outboard =
caliper-half is fairly simple, with an adjustable screw and lock nut that =
sets the clearance between the pad and rotor. There is an "O" ring on this =
shaft that seals it from the outside and since it is adjusted only rarely =
I don't think this is the problem area." =20

Now, I wonder if it's true that the function of that "O" ring is to seal =
the system from the outside?  Seems to me that this O-ring is mainly there =
as a hydraulic seal, sealing the hydraulic pressure in.  The hydraulic =
pressure cavity behind the piston seems to have two possible leakage =
routes to the outside world..... the first being out round the sides of =
the piston, which is sealed by the main piston seal of course,  and the =
other being behind the piston, which I expect is sealed by this O-ring on =
the outer adjuster shaft. I'd be interested to hear any thoughts on this =
please, as I'd like to know how critical this O-ring is, as it's hard to =
find the exact replacement.  If it's only an external dust seal, no sweat, =
but if it's a hydraulic pressure seal, different story......

Best regards,
Graham in NZ
(77 Alfetta, 71 GTV, 82-82-84 Alfasuds)

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