James,
I think the "Common Wisdom", which seems to apply only about half the
time, is that ball bearing throwouts (don't know if there is such a
thing as a "roller" bearing throwout) are not meant to turn
continuously, unlike, say, tapered roller wheel bearings. I could be
wrong. I know that in at least one Toyota I've owned, there is
actually a return spring on the slave cylinder to make sure the
bearing doesn't make constant contact with the clutch cover.
Individual driving styles and experiences, as well as
parts/manufacturers may vary, void where prohibited by law.
To be honest, you are the first person (out of about seven I know
of--a statistically insignificant basis for True Knowledge) who
hasn't had what they feel was a bad experience. (Could I get you to
buy me a Lottery ticket?) If Doug isn't installing them himself,
probably sees only the (X)% of cars in his region with problems.
Shorter lifespan is not the same thing as defective, so I don't know
if the manufacturer would care--and I know what VB would say if you
called them up after a couple year's use. (Service is, after all,
their middle name!) I'm interested in other people's experiences.
(I'm not quite ready to become the Secretary of the MG Throwout
Bearing Registry--North America--yet.)
I gotta say, my personal experience with "new, improved, better than
OEM" high performance parts makes me at least as skeptical as you
seem to be. Let's see--headers that crack or warp, aluminum Alfa
camber adjusters that quickly wore out, the Strowski Overdrive
Transfer Case for 3 speed LandCruisers (I still have it in a box, if
anyone is interested...)
Chris
>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
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