R. Johnson wrote:
rj> ...[snip]...
rj> An option to the stock carbon throw-out bearing is a roller type
rj> throw-out bearing for about $50 extra. I have installed these
rj> instead of the stock carbon type. In an e-mail awhile back from
rj> Dick Criswell, he said he didn't recommend them. Unfortunately,
rj> I was never able to find out just what his thoughts on the matter
rj> were before his accident. VW Beetle's came with carbon
rj> throw-out bearing for years as well as MGs. I guess there's really
rj> nothing wrong with them. I'm sure this will start an interesting thread...
rj> ...[snip]...
The following is from Doug Jackson's 'excellent' "British Automotive"
web site ... http://www.mgbmga.com ...
dj> Before you consider installing aftermarket ball/race type throw out
dj> bearings, be sure to read the following information. If you have already
dj> installed this type of bearing, it is doomed to failure. Presently there
dj> are two styles of ball/race type bearings available:
dj>
dj> 1. - A black plastic housing type
dj> 2. - A steel housing type
dj>
dj> Both of these types of bearings suffer from premature "run-dry"
dj> conditions and their failure is directly related to being in continual
contact
dj> with the clutch cover thrust pad. No.1 will self destruct in a very short
time;
dj> No.2 will survive much longer and failure will not be as catastrophic.
dj>
dj> The OEM designed slave cylinder (hydrostatic) eliminates the need for
dj> clearance between the throw out bearing face and the clutch cover thrust
dj> pad; these two parts are always in contact with each other. This system
dj> was also self compensating for clutch disc wear and the OEM throw out
dj> bearing survived reasonably well under these conditions. Although other
dj> manufacturers use similar hydraulic systems, the MGB, with its larger slave
dj> cylinder diameter (1.25"), has a high residual hydraulic pressure which is
dj> then multiplied by the throw out bearing release arm leverage ratio. This
dj> residual hydraulic pressure acts directly upon the throw out bearing face
and
dj> the clutch cover thrust pad. Any increase in clutch hydraulic residual
pressure
dj> will only compound the wear rate of both these types of ball/race throw out
dj> bearings.
dj>
dj> If you have already fitted a ball/race type throw out bearing, or are
intending
dj> to fit one, then you should install British Automotive's clutch clearance
stop
dj> kit P/N STOP/KIT; this will allow approximately 1/16" to 1/8" clearance
dj> between the throw out bearing and the clutch cover thrust pad when the
dj> clutch is not in use thereby preventing this type of bearing from premature
dj> "run-dry" conditions. Fitment of this kit will also ensure the longevity of
the
dj> OEM type throw out bearing and is recommended for both the MGB and
dj> MGA systems.
Usual disclaimers ... I am not affiliatied with "British Automotive" ... YMMV
Safety Fast! ...larry.g.unger@lmco.com
'61 MGA 1600 MkII
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