What's With Bottom Brackets?

All,

Many BB's now come with one cup made of plastic or carbon or some such
material. These materials don't sound too durable, to me.

What's the matter with cups being made of steel?

Thanks!

Phil

wrote in message
oups.com...
All,

Many BB's now come with one cup made of plastic or carbon or some such
material. These materials don't sound too durable, to me.

What's the matter with cups being made of steel?

Thanks!

Phil


With the drive-side threads actually part of the cartridge, the other side
doesn't need a cup to be much more than a shim. It's not holding the
cartridge in at all, it's mostly preventing it from moving up, down, back
and forth. Plastic does the job well enough, and weighs and costs less.

the new all steel 5500 BB came in last week and ima pleased as gatorade
but i put a not delrin poly water bottle shim in bewteen the seat
clamps ummmmm
over a year ago ride every day take the seat off once a day
a chunk fell of a few days ago that it - one chunk -
wroks well in compression - no bending.

Phil who? writes:

Many BB's now come with one cup made of plastic or carbon or some
such material. These materials don't sound too durable, to me.

What's the matter with cups being made of steel?

Well, how about what's wrong with plastic first? What the designers
of these BB's seem not to understand is that plastic is PLASTIC and
can flow with either heat or load or both. I believe these bearing
cups/retainers are no better than the plastic ball and cup head
bearings of the 1950's, that didn't suffer from fretting damage but
flowed to the same result. The thinking was in the right direction
but the solution wasn't up to the problem.

If the loads are great enough to spall cups and spindles of old style
1/4" ball BB's, then I am sure the loads are too great for plastic
bearing retainers.

Jobst Brandt

On 21 Jun 2006 14:27:05 -0700, wrote:

All,

Many BB's now come with one cup made of plastic or carbon or some such
material. These materials don't sound too durable, to me.

What's the matter with cups being made of steel?

Steel has been low-end for about a decade. Aluminum is still used for
the majority of good BB assemblies other than Shimano. The only
plastic ones I've run across are the left retainers for some of the
Shimano UN-series BBs. Even those work; there's little actual strain
on them, in fact.
--
Typoes are a feature, not a bug.
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wrote:
All,

Many BB's now come with one cup made of plastic or carbon or some such
material. These materials don't sound too durable, to me.

What's the matter with cups being made of steel?

Thanks!

Phil


It's not the cup that's made of plastic, but the threaded bushing that
supports the end of the cartridge. That is a perfect application for
plastic. In practice, it will outlast the bearings and never corrode.

"Peter Cole" wrote in message
. ..
wrote:
All,

Many BB's now come with one cup made of plastic or carbon or some such
material. These materials don't sound too durable, to me.

What's the matter with cups being made of steel?

Thanks!

Phil


It's not the cup that's made of plastic, but the threaded bushing that
supports the end of the cartridge. That is a perfect application for
plastic. In practice, it will outlast the bearings and never corrode.

And thus come out of the frame easily too ... and not stuff the threads if
you don't get it started right.

Skippy
E&OE

i'd say its a technicallity
having 1 side 'loose' provides safety against bending
like they build bridges / on side is build on rollers (here in halland
at least)

still, plastic that comes loose by default is a bad design (I use gas
tape to keep it stuck)


On 21 Jun 2006 14:27:05 -0700, wrote:

All,

Many BB's now come with one cup made of plastic or carbon or some such
material. These materials don't sound too durable, to me.

What's the matter with cups being made of steel?

Thanks!

Phil

If the loads are great enough to spall cups and spindles of old style
1/4" ball BB's, then I am sure the loads are too great for plastic
bearing retainers.

Jobst Brandt

Jobst: To the best of my knowledge, there are no commonly-available (on
decent bikes) plastic bearing retainers in use. I believe the original
poster is talking about a cartridge bottom bracket that's held in place, on
one side, by a plastic threaded-in... cup? Retainer? I'm not sure what you
call it, but I think you're familiar with what I'm talking about. Rarely do
they cause any grief, but they're not found in anything very expensive (over
$500) either.

--Mike Jacoubowsky
Chain Reaction Bicycles
www.ChainReaction.com
Redwood City & Los Altos, CA USA

wrote in message
...
Phil who? writes:

Many BB's now come with one cup made of plastic or carbon or some
such material. These materials don't sound too durable, to me.

What's the matter with cups being made of steel?

Well, how about what's wrong with plastic first? What the designers
of these BB's seem not to understand is that plastic is PLASTIC and
can flow with either heat or load or both. I believe these bearing
cups/retainers are no better than the plastic ball and cup head
bearings of the 1950's, that didn't suffer from fretting damage but
flowed to the same result. The thinking was in the right direction
but the solution wasn't up to the problem.

If the loads are great enough to spall cups and spindles of old style
1/4" ball BB's, then I am sure the loads are too great for plastic
bearing retainers.

Jobst Brandt