in message <[email hidden]>, Anthony
Jones (') said:Simon Brooke said:But you don't need a larger diameter BB shell /unless/ you're sticking
gears in there. BB bearings do wear out in time, but so does anything.
They don't (if reasonable quality) wear out very quickly, and they are
not complex or expensive to replace. Outboard bearings are just the
current step in Shimano's on-going planned obsolescence programme. As
with splined bottom brackets and hollow bottom bracket axles there's
no particular technical benefit, but you'll have to buy all new again
in two years when Shimano introduce the Next Big Thing (probably a
bigger shell).A larger diameter BB shell would allow the use of an ISIS bottom
bracket with larger bearings. ISIS is an open standard, so hopefully it
will be around for a while, but since it requires a larger diameter
spindle the bearings have to be small to fit in the BB, hence rubbish
bearing life by most accounts.As for my cranks becoming obsolete, you're right -- I'd much rather not
be at the mercy of Shimano's obsolescence plans. But I don't think
it'll happen within 2 years (other manufacturers are already making
compatible bearings), and even if it's only 5 years before I can no
longer get parts, it's still lasted better than any square taper cranks
I've had.
H'mmm... I've three square taper systems still in use. One's 18 years and
about fifteen thousand miles old (cranks; the BB's been replaced at
least twice, probably more times, and the rings have all been replaced);
ones's fourteen years and about thirty thousand miles old (don't think
anything's been replaced yet, but the crankset is about due for
replacement); one's two years and about four thousand miles old (nothing
replaced yet, no problems).
--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/
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