brake conversion-wilwood

[Bernie Benz]

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Scott and Keith,

My point is based on the fact that reliable 0-ring and Quad ring seals must
be protected from the ingestion of even small particles and quanities of
dirt.
That's why shocks and all industural hydraulic cylinders use rod scrapers as
the outside protection from such intrusions.  Inasmuch as this road grime
cannot be cleaned from the piston surface, short of disassembly, within the
small piston to bore clearance and the sharp accute angle formed at seal to
piston interface, it will be ingested if the piston is forced back into the
bore.

Mark's response from "Todd Howerton" <ToddH at outlawdiscbrakes.com>
Subject: DUST SEALS indicated that Wilwood pistons are stainless steel and
he did indicate that some use Keith's "trick" in servicing pads, but hardly
a recomendation, IMO.  Therefore, from a seal reliability standpoint, in the
absence of dust boots the piston should never be forced back into the
caliper without disassembly and cleaning.  And there is absolutely no good
reason for doing so.  A little ss hanging out in the breeze incours no harm,
but don't abuse your seals!

Bernie


From: QSHIPQ at aol.com
Date: Sat, 11 May 2002 03:12:16 EDT
To: b.m.benz at prodigy.net
Cc: DasWolfen at aol.com
Subject: Re: brake conversion-wildwood


Not at all with you bernie.  first, keith was referencing non seal calipers.
Second, read the "response" from Mark Chang's dust seal inquiry.  Third,
look at the difference between aftermarket pads and the stock textars on Big
Red applications.  Fourth, having just done this "trick" at Grattan a couple
weeks ago (with keith helping me rebuild the brakes), it's very obvious that
exposing less piston to the elements is a good thing.  Dust seals or not.
For more on the dust seal "exposure" you could do an archive search, when I
was serving up MGW a huge plate of humble pie wrt big reds.

SJ
In a message dated 5/10/02 9:49:10 PM Central Daylight Time,
b.m.benz at prodigy.net writes:


I judge that this "trick" is pure conjecture on your part.

As a new pad wears the seal is always presented with clean piston from the
inside.  The dirty side of the piston never moves inward relative to the
seal, inasmuch as piston movement due to changing braking pressure is
comprised totally of seal deflection, not relative movement between the two
parts.  Therefore, from a hydraulics perspective, overhaul and parts
cleaning is only necessary when replacing pads.  Road salts may have an
adverse effect on the aluminum parts even though they are hard anodized, but
this is another factor and circumstance.

Your "trick" of adding shims before pad replacement.requires unnecessary
caliper overhaul with each shim addition, IMO.

Bernie
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