[TR] [Spits] clutch hydraulics query

[Joe Curry]

I had this problem with the front brake cylinder on Tiny Tim after I
installed the Tilton balance bar.  What was happening was the piston was not
being allowed to come far enough forward to relieve the pressure in the
line. As a result, after a few cycles of braking, the pressure would build
up and lock the pads to the rotors.

Cracking the bleed valve was enough to reset the system, but redoing the
push rod on the master cylinder was required to fix the problem.

Joe

-----Original Message-----
From: spitfires-bounces at autox.team.net
[mailto:spitfires-bounces at autox.team.net] On Behalf Of jimmuller at rcn.com
Sent: Thursday, March 26, 2009 12:15 PM
To: Triumphs at autox.team.net; Spitfires at autox.team.net
Subject: [Spits] clutch hydraulics query

I drove my GT6 in to work this morning.  I'm happy to report that the
gearbox worked just fine.

I must report unhappily that the clutch is more needy, which is to say less
clutchy.  It's a problem I've wrestled with before.

As I'm driving it seems to build pressure in the hydraulics so that
eventually the clutch slips.  The quick fix is to crack open the nut where
the line goes into the master cylinder, allowing a teaspoon or so of clutch
fluif, which is to say brake fluif to escape.

It did this a few days ago on a brief drive.  It did it again this morning
while I was tooling down the highway.  A common condition for most occasions
that I recall is that it was cold when I started out.  And I suspect that if
I mash the pedal down too hard it can bring on this condition.  Or least not
mashing it hard seemed to have avoided it for a long time.

I'd suspect a sticky slave cylinder except that this morning it seemed to
have come on when I wasn't using the clutch at all.  At least not that I
recall.  Okay, maybe once.  An alternate stickiness factor could be the
clutch arm scraping against the tunnel cover.  I can check it but it's one
of those space-age plastic covers with no dangling insulation underneath, so
I doubt this possibility.  It really seems to correlate to heat.

So the question:  Is there evidence to suggest that brake fluif expands
noticeably with moderate heat?  (It isn't getting especially hot.)  Perhaps
older fluif that might have absorbed water sitting even in an opened once
but tightly sealed container?

Of course, the obvious fix is just to purchase new cylinders, clear out the
line, then use DOT5.  Spitbits lists the SC at about $50, the MC OEM for
about $150 and MC repro for about $65, IIRC.

tanks,
Jim Muller
'70 GT6+
'80 Spitfire
Spitfires at autox.team.net
http://autox.team.net/mailman/listinfo/spitfires

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