List:
There's been several messages recently about failed release (throw out)
bearings. Thought I'd add my two cents worth.
After 20 + years and more than 250,000 miles on a TR250 and 2 TR6s, plus
junkers and friends cars, etc. I've seen at least 25 and probably 50 release
bearings, never seen one that has failed and have put well over 50,000 miles
on several and over 100,000 on one (that one was used by my daughter
through four years of college. She never let a clutch out gently --- she
loved the noise the tires made when starting.) I've taken several from
cars that probably had close to 100,000 miles on them. I always use the
stiff Borg & Beck clutch and standard (inexpensive) bearings
This bearing is old technology, is fairly large for the job and has a very
low duty cycle. Compared to wheel bearings, the load is fairly light. I
don't believe the new bearings are of low quality --- I haven't had any
trouble with them. (I have no data on the higher priced Toyota
bearings --- they may have quality problems or there may be a problem using
a bearing in a system for which it was not designed.)
I've seen wheel bearings fail quickly --- when installed improperly. I
suspect that many of the release bearing failures are do to damage caused
when the bearing is pressed onto the sleeve. One thing I've noticed that is
different recently is that most of the new sleeves are hardened. Pressing a
hardened bearing onto a hardened where the pressing forces must be
transferred through the bearing surfaces seems to be a likely source of
bearing damage.
I never purchased the assembled sleeve-bearing combinations and likely
won't because I have no idea how the bearing was pressed onto the sleeve.
A technique I use to minimize forces during the pressing operation is to
cool the sleeve in the freezer for a few hours and to heat the bearing to
200 degrees or so. I then press them together with a inexpensive tool from
TRF that rotates the bearing as it is pressed on. The bearings seem to go
on the sleeve with little force and I'm fairly confident that they are not
damaged. (I've seen notes where people have access to liquid nitrogen. They
cool the sleeve with the nitrogen and then the bearing can be dropped drop
into position without heating it and with no force).
Hope this extends the life of some TOBs -- life is too short to be pulling
the same gearbox every year or so.
Nelson Riedel
Granville, OH
76 TR6 (assembling after new paint)
68 TR250 (next project - new paint)
70 TR6 (all the parts in a pile ready to assemble)
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