Bruce,
I'm unsure if this applies to the rear pistons on a 105 but a lot of Alfa
pistons have a cutaway section on the piston where it contacts the back of
the pad. If the piston is rotated to the incorrect orientation , or at
least different to the opposing caliper, it can make one side 'grab' or
self-servo more than the other. It's usually noticeable on the fronts.
A long shot, but costs little to confirm or dismiss.
I'd also suspect any bias distribution valve in the braking system.
Have you confirmed your symptoms with the car on jackstands, or only when
driving? Other longshots to check would be to confirm that both rear
calipers are the same model type, and that the pads, backing shields etc are
identical (or mirror-images) and that everything is in the correct place and
orientation side-to-side.
Beatle
Oz
----- Original Message -----
From: "Bruce giller" <[email protected]>
To: "Alfa Digest" <[email protected]>
Sent: Tuesday, December 01, 2009 2:21 AM
Subject: [alfa] brake caliper operates independently
Yes, the left rear brake caliper on my GTV has a mind of its own. When it
is cold, it acts in unison with the other calipers when I press&release
the
brake pedal. But in about 10 minutes, it maintains a slight grip on the
rotor which is very apparent with gliding to a stop or accelerating
slightly in heavy traffic. The grip appears to increase but in about 20
minutes, the caliper is again playing by the rules.
I experienced this condition early last month after the car had been
sitting
for a few months (waiting for a driver's event to attend). I 'exercised'
the two pistons in the driveway by pushing each piston into the caliper
and
then extending it more than normal (used a thin piece of wood to make sure
it did not come all the way out). I noticed that the dust shield was very
brittle as if subjected to high temps; I couldn't see any corrosion on the
piston but my view was limited.
I'd suspect the rear flexible brake hose of becoming clogged but I
replaced
it with some SS hose about 10 years back; and the right rear caliper
doesn't
misbehave at all. And usually if the caliper is grabby when warm, then it
stays that way. The left one seems to get grabby within a certain temp
range and then is normal at 'full operating temp'. Anyone ever
experienced
this ??
I'll be rebuilding the caliper this winter.
Bruce
'73 GTV
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