Paul H.,
I believe the original purpose of the cutouts was to prevent brake
squeal. If so, it would make sense to me to orient the cutout toward
the trailing edge of the pad. This would have the effect of "toeing in"
the leading edge of the pad, much like they do on bicycle brakes to
prevent squeal. I believe many of the new pistons are being supplied
with no cutouts, the anti-squeal function now being handled by shims
between the piston and pad.
As for rotating the pistons in the caliper, I have always been
successful using a piston removal tool, this looks like a pair of
internal acting right-angle pliers, with serrated teeth that grip the
inside surface of the piston. The comment of the other lister (on the
MG BBS) doesn't make sense to me - even though the caliper piston seal
has significant friction in its channel, the piston should still turn
within the seal. If not, I would suspect piston damage (unlikely on new
calipers).
A friend of mine had an unusual problem on a 4-cylinder B roadster. He
always experienced a slight pull to one side under light braking, but if
he put his foot into it, the car would stop straight. He finally
tracked it down to one caliper having cutout pistons, and the other
having flat ones! These were both rebuilt calipers installed new at the
same time.
My V-8 calipers are both sitting on my garage floor - the bodyshell went
to the bodyman last week. I noticed that the calipers have shims behind
the pads, but I have not checked whether or not they have cutout pistons
yet.
Cheers, PK
> ----------
> From: Paul Hunt[SMTP:paul.hunt1@virgin.net]
> Reply To: Paul Hunt
> Sent: Sunday, July 19, 1998 7:42 AM
> To: mgb-v8@autox.team.net
> Subject: Calipers
>
> I have just replaced the calipers on my factory V8. The old
> calipers do not have a cut-out in the piston where it
> contacts the pad, but the new calipers do. My V8 Workshop
> Supplement does not contain a section on brakes although
> it is listed in the index (the index varies from the actual
> contents elsewhere as well), but the 1800 Manual states that the
> cut-out must be located towards the hub. The cut-outs on the
> new calipers all face upwards when the calipers are mounted
> i.e. towards the trailing edge of the pad. I tried rotating
> one of the pistons but it would not budge, even though they
> all move in and out smoothly (much better than the old
> calipers).
>
> I find it difficult to believe that all the cut-outs have
> landed up in this position purely by chance, but wonder at
> the difference to the 1800 manual.
>
> Any comments or suggestions?
>
> PaulH.
>
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