I can hardly wit to hear your findings.
Don Collins wrote:
> Well this is a very good time for this thread. About 2 weeks ago my B
> started having some vibration when ever the clutch was pushed in. Deciding
> it was time to get it home I took off and the next gear change the clutch
> went to the floor, major grinding sounds, and smoke coming out from under
> the car. I was able to place the car in 1st to get going w/out using the
> clutch and then high speed shifted it to 3rd and ran in 3rd o/d to get it
> home (no slippage in the clutch when I accelerated. Engine was running
> fine). I will be pulling the engine in about 2 weeks after I move into my
> new house to see what happened. This is a Roller T.O. Bearing that was
> replaced in 1995. If this was the cause then looks like it will be back to
> the stock T.O. bearing. Hard to say but it has only been 4 years and under
> 15K miles.
> Has anyone had this same thing happen?
>
> Don Collins
> 70B
> 70BGT
>
> -----Original Message-----
> From: owner-mgs@autox.team.net [mailto:owner-mgs@autox.team.net]On
> Behalf Of James H. Nazarian
> Sent: Wednesday, October 20, 1999 5:26 PM
> To: Max Heim
> Cc: MG Listserver
> Subject: Re: Roller Throwout Bearing
>
> Maybe that explains why the roller bearings sometimes work (concentric) and
> sometimes don't (eccentric). Good 'splanation Max!
>
> Jim
>
> Max Heim wrote:
>
> > I think someone said the issue was concentricity; i.e. the MGB clutch arm
> > is not designed in such a way as to perfectly center the throwout bearing
> > on the axis of rotation, every time. For the "friction" type of bearing,
> > this doesn't really make any difference, which explains the
> > "shortcomings" of the original design in this context. But the roller
> > bearing assumes concentricity of rotation.
> >
> > Think about it. If the axis of rotation of the roller bearing, when
> > applied, doesn't precisely match the center of rotation of the clutch
> > disc, you get an effect like a tiny bicycle crank. This would cause
> > vibration, and enormous side stresses on the bearing, which it might not
> > be designed to support for long.
> >
> > Of course, if your clutch arm components and bushings were all new, you
> > might have something close to concentricity, and thus enjoy reasonably
> > long roller bearing life (as many have reported). But if your clutch arm
> > was anything like mine (when I last replaced my clutch), with worn-out
> > bushings and pins and ovaled-out holes, no two clutch pedal applications
> > would result in the same alignment, and you'd probably experience
> > catastrophic or premature failure (as has also been reported).
> >
> > Anyway, I think that is a plausible explanation of both sides of this
> > situation...
> >
> > James H. Nazarian had this to say:
> >
> > >Chris,
> > >
> > >I quote British Automotive:
> > >
> > > "Before you consider installing aftermarket ball/race type throw out
> > >bearings,
> > > be sure to read the following information. If you have already
> installed
> > >this type
> > > of bearing, it is doomed to failure. Presently there are two styles
> of
> > >ball/race
> > > type bearings available:
> > >
> > > 1.- A black plastic housing type
> > > 2.- A steel housing type
> > >
> > > Both of these types of bearings suffer from premature "run-dry"
> > >conditions
> > >and
> > > their failure is directly related to being in continual contact with
> the
> > >clutch cover
> > > thrust pad. No.1 will self destruct in a very short time; No.2 will
> > >survive much
> > > longer and failure will not be as catastrophic."
> > >
> > >Why would a sealed, permanently lubricated roller bearing designed for
> > >continuous operation with load applied along the axis of rotation, run
> dry?
> > >Could it be defective? Or damaged during installation? If so, was it
> returned
> > >to and examined by the manufacturer? If so, might we see their analysis
> or
> > >reply? If Doug's right, I've been driving several time bombs for the past
> 15
> > >years. Maybe Doug will share some of his exhaustive test data and methods
> > >with
> > >us.
> > >
> > >Before I ask Mr. Moss to fly out to Ohio to help me change all these
> heavy
> > >duty
> > >roller bearings back to the original graphite type, I think I need to see
> > >some
> > >proof. Thanks in advance for enlightening us.
> > >
> > >Senior Doubting Thomas
> > >
> > >AKA Jim
> > >1960 MGA
> > >1974 MGB-GT
> > >and a pool of other octagonal delights
> > >
> > >Chris Attias wrote:
> > >
> > >> Peter C. wrote:
> > >> "A few quick thoughts. Roller bearing or carbon.... don't "ride" the
> > >> clutch. The only time that a clutch can become worn is when your foot
> is on
> > >> the pedal. If you don't touch the pedal, the clutch wont wear."
> > >>
> > >> This seems to disagree with what I understood about the design of the
> > >> MGB Borg & Beck clutch assembly. See Doug Jackson's write-up on
> > >> clutch bearings @ www site:
> > >> http://www.mgbmga.com/tech/index.html
> > >>
> > >> While I realize Doug has some commercial interest in his development
> > >> of a fix for the problem he finds with roller bearings, he does
> > >> exhaustive research and shares his experimentation and research
> > >> freely...(No commercial interest disclaimer...)
> > >> Chris Attias
> > >> '64 MGB
> > >> '84 Alfa Romeo GTV-6
> > >
> > >
> >
> > --
> >
> > Max Heim
> > '66 MGB GHN3L76149
> > If you're near Mountain View, CA,
> > it's the red one with the silver bootlid.
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