The finish of the caliper pistons is not hyper-critical. Just as in
rebuilding master cylinders the seals do have to bed against something,
so satin finish is better than a surface worn to a polish. So long as
there are no pits the pistons should be reusable.
We have been getting pistons that have a black almost Parkerized finish,
that look weird but seem to work well.
The aftermarket GT wheel cylinders at Moss are made by Brake Engineering
in the UK and are a good unit. The "OE" Delphi Lockheed ones have
always been very expensive and in this case the aftermarket ones are a
good way to save money, with no real downside. I think Delphi is
sourcing the snap ring from the same supplier, so they are going to be
both about as much of a pain to install. Too soft of a snap ring can
make installation more difficult. See the archives for suggestions on
install, or replacement with a circlip.
If you want a chance to drive the Miata, I can send your wife photos of
my 99 Miata after it was rear ended by a Peterbilt Truck. Unfortunately
the plot would likely rebound and she would end up making you buy a pair
> -----Original Message-----
> From: email@example.com [mailto:firstname.lastname@example.org] On
> Of David Ambrose
> Sent: Sunday, January 30, 2005 9:45 AM
> To: MG Mailing List
> Subject: Need some brake rebuilding advice
> I tore into the wheel end of my 69 BGT yesterday and came up with a
> couple of questions:
> 1) The pistons in one caliper have a satin finish as opposed to the
> usual shiny finish. Can I reuse these pistons, or should I go ahead
> replace them?
> 2) Both rear wheel cylinders need replacement. I see Moss lists two
> types of cylinders, OEM, and aftermarket. Are the aftermarket
> good, or should I stick with the OEM?
> It's already top-down motoring here in San Diego, though the mornings
> are pretty cold. Alas, my wife gets to drive the Miata most of the
> --Dave Ambrose