Revenge of the bottom bracket

Hello!

Thanks to everyone who responded to my question about a wobbly bottom
bracket last month. I finally took it into a LBS to get a new BB this
week, but all did not go well.

My old BB has plastic threaded bits. Question 1: are these what are called
cups? My mechanic expressed surprise at this, saying he'd never seen a BB
with two plastic threaded bits before. Sometimes one or the other, but not
both. Question 2: does that seem plausible?

The mechanic tried to take it out, but found it was seized. He applied a
bit more force, and sheared the female splines on the threaded bit. He
then repeated the procedure on the other side of the BB.

So, i have gone from a bike with a wobbly bottom bracket, to a bike with a
wobbly bottom bracket which i now know to be seized, and has sheared
splines.

I suppose what i need to do is get the bracket out somehow. Question 3:
how?

The mechanic talked about digging the plastic out with a sharp instrument.
That sounds reasonable. Can anyone suggest another technique?

Another option might be to take it to someone a bit more engineeringish
than me, who can put a bloody great drill through it or something, and get
more leverage on the threads. I know someone who might be able to do that.

Grr.

tom

--
And the evening and the morning were the fifth day.

On Fri, 29 Jul 2011 18:05:44 +0100
Tom Anderson wrote:

Hello!

Thanks to everyone who responded to my question about a wobbly bottom
bracket last month. I finally took it into a LBS to get a new BB this
week, but all did not go well.

My old BB has plastic threaded bits. Question 1: are these what are
called cups?

Sort of - with the old steel cup/cone/balls bearings they would be the
cups, with the sealed ones they sit in the same place as the cups but
don't do any of the bearing work. People probably still call them
cups, but technically they should probably be called something like a
threaded bush.

My mechanic expressed surprise at this, saying he'd
never seen a BB with two plastic threaded bits before. Sometimes one
or the other, but not both. Question 2: does that seem plausible?

Makes your mechanic sound inexperienced.

The mechanic tried to take it out, but found it was seized. He
applied a bit more force, and sheared the female splines on the
threaded bit. He then repeated the procedure on the other side of the
BB.

So, i have gone from a bike with a wobbly bottom bracket, to a bike
with a wobbly bottom bracket which i now know to be seized, and has
sheared splines.

I suppose what i need to do is get the bracket out somehow. Question
3: how?

The mechanic talked about digging the plastic out with a sharp
instrument. That sounds reasonable. Can anyone suggest another
technique?

Another option might be to take it to someone a bit more
engineeringish than me, who can put a bloody great drill through it
or something, and get more leverage on the threads. I know someone
who might be able to do that.

Drill a ring of holes close together all round the plastic, as close to
the bottom bracket shell as you can without damaging the threads, and
all the way through to the metal bearing. If you have a deep
enough holesaw the right size that's even better. Press the axle
through from the other side using a large vice or a press - support the
bottom bracket shell with a large socket or similar. Chisel the remains
of the plastic out with an old screwdriver. On the other side slot the
plastic in several places with a hacksaw before chiselling that out too.
If you get to the point of giving up on it find someone with
oxy-acetylene who can burn it out (will probably need the threads
cleaning up with a tap afterwards, and the paint will be a mess).

On Sat, 30 Jul 2011, Rob Morley wrote:

On Fri, 29 Jul 2011 18:05:44 +0100
Tom Anderson wrote:

Thanks to everyone who responded to my question about a wobbly bottom
bracket last month. I finally took it into a LBS to get a new BB this
week, but all did not go well.

My old BB has plastic threaded bits. Question 1: are these what are
called cups?

Sort of - with the old steel cup/cone/balls bearings they would be the
cups, with the sealed ones they sit in the same place as the cups but
don't do any of the bearing work. People probably still call them cups,
but technically they should probably be called something like a threaded
bush.

I do like a threaded bush. Although i wonder if only one of them is a
threaded bush, the other, the one fixed to the bracket, being something
else. Certainly the best suggestion i've heard yet, though!

My mechanic expressed surprise at this, saying he'd never seen a BB
with two plastic threaded bits before. Sometimes one or the other, but
not both. Question 2: does that seem plausible?

Makes your mechanic sound inexperienced.

Yes, that's what i thought. He is a young guy, and the bike shop is new
and trendy; i get the impression it's some guys who thought they fancied
running a bike shop living the dream. He does seem pretty knowledgeable
and helpful, perhaps the sort of person you might have found on urc in its
heyday.

The mechanic talked about digging the plastic out with a sharp
instrument. That sounds reasonable. Can anyone suggest another
technique?

Drill a ring of holes close together all round the plastic, as close to
the bottom bracket shell as you can without damaging the threads, and
all the way through to the metal bearing. If you have a deep enough
holesaw the right size that's even better. Press the axle through from
the other side using a large vice or a press - support the bottom
bracket shell with a large socket or similar. Chisel the remains of the
plastic out with an old screwdriver. On the other side slot the plastic
in several places with a hacksaw before chiselling that out too. If you
get to the point of giving up on it find someone with oxy-acetylene who
can burn it out (will probably need the threads cleaning up with a tap
afterwards, and the paint will be a mess).

Hmm. I'm afraid that passed by ability at 'drill', but i might know
someone who can do this.

Cheers for the suggestion.

tom

--
skin thinking

On Sat, 30 Jul 2011 18:57:29 +0100
Tom Anderson wrote:

I do like a threaded bush. Although i wonder if only one of them is a
threaded bush, the other, the one fixed to the bracket, being
something else. Certainly the best suggestion i've heard yet, though!

It's possible they're both the same (apart from the thread direction)
with the bearing assembly sitting loose between them, although you're
right that more usually the drive side is part of a complete bearing
assembly while the other side isn't attached.

Tom Anderson wrote:

Hello!

Thanks to everyone who responded to my question about a wobbly bottom
bracket last month. I finally took it into a LBS to get a new BB this
week, but all did not go well.

My old BB has plastic threaded bits. Question 1: are these what are
called cups? My mechanic expressed surprise at this, saying he'd
never seen a BB with two plastic threaded bits before. Sometimes one
or the other, but not both. Question 2: does that seem plausible?

The mechanic tried to take it out, but found it was seized. He
applied a bit more force, and sheared the female splines on the
threaded bit. He then repeated the procedure on the other side of the
BB.

So, i have gone from a bike with a wobbly bottom bracket, to a bike
with a wobbly bottom bracket which i now know to be seized, and has
sheared splines.

I suppose what i need to do is get the bracket out somehow. Question
3: how?

The mechanic talked about digging the plastic out with a sharp
instrument. That sounds reasonable. Can anyone suggest another
technique?

Another option might be to take it to someone a bit more
engineeringish than me, who can put a bloody great drill through it
or something, and get more leverage on the threads. I know someone
who might be able to do that.

Sounds weird .. or it's a very cheap bike ..

You could try drilling two holes in it, either side of centre along a
diameter such that you can use an angle grinder type tool to try and
unwind the thread.

Is the pedal spindle still in? If it's out, thread a hacksaw blade
through, re-connect the hacksaw and slot the cups till you can break
them up with a chisel.

If the spindle is in, use a long drill to drill a hole through both
ends so you can again thread a hacksaw/coping saw blade through and use
it to cut as above ..

Probably lots of variations on the above .....

--
Paul - xxx

On 31 Jul 2011 14:49:07 GMT
"Paul - xxx" wrote:

Sounds weird .. or it's a very cheap bike ..

FAG make all-plastic cartridge bottom brackets, they were one of the
first sealed units available at a reasonable price (and also ISTR one
of the first to use the cartridge design that's common today - previous
models had a separate "cup" on each side and bare bearings between). A
few smaller manufacturers (e.g Orbit, Saracen?) used them on reasonable
quality bikes, before Shimano and similar types became common.

On 29/07/2011 18:05, Tom Anderson wrote:
Hello!

Thanks to everyone who responded to my question about a wobbly bottom
bracket last month. I finally took it into a LBS to get a new BB this
week, but all did not go well.

My old BB has plastic threaded bits. Question 1: are these what are
called cups? My mechanic expressed surprise at this, saying he'd never
seen a BB with two plastic threaded bits before. Sometimes one or the
other, but not both. Question 2: does that seem plausible?

The mechanic tried to take it out, but found it was seized. He applied a
bit more force, and sheared the female splines on the threaded bit. He
then repeated the procedure on the other side of the BB.

So, i have gone from a bike with a wobbly bottom bracket, to a bike with
a wobbly bottom bracket which i now know to be seized, and has sheared
splines.

I suppose what i need to do is get the bracket out somehow. Question 3:
how?

The mechanic talked about digging the plastic out with a sharp
instrument. That sounds reasonable. Can anyone suggest another technique?

Another option might be to take it to someone a bit more engineeringish
than me, who can put a bloody great drill through it or something, and
get more leverage on the threads. I know someone who might be able to do
that.

Grr.

tom


Normal BBs on the kind of bike you describe are usually a metal sealed
cartridge on the right side (chain side ) , with a left-hand thread; and
a plastic support cup on the other side with a normal rh thread that
does nothing much except keep the thing centralised.

You ought to be able to remove the left support cup easily, but the RH
one can be tight. But do remember it's a LH thread.

If both sides are plastic, and the splines have sheared, then use
whatever method you can to remove the POS from the frame, destructive or
not. If you can do something that can gain purchase on the BB and
un-screw it, then go for it. Otherwise, any destructive removal is
fine, so long as you don't damage the threads on the frame.

Clean up the threads on the frame ( try to avoid re-tapping if you can )
and install a modern shimano BB cartridge.

--
Ron

Rob Morley wrote:

On 31 Jul 2011 14:49:07 GMT
"Paul - xxx" wrote:

Sounds weird .. or it's a very cheap bike ..

FAG make all-plastic cartridge bottom brackets, they were one of the
first sealed units available at a reasonable price (and also ISTR one
of the first to use the cartridge design that's common today -
previous models had a separate "cup" on each side and bare bearings
between). A few smaller manufacturers (e.g Orbit, Saracen?) used
them on reasonable quality bikes, before Shimano and similar types
became common.

I stand corrected.

--
Paul - xxx

On Mon, 01 Aug 2011 19:31:34 +0100
Ron Lowe wrote:

Clean up the threads on the frame ( try to avoid re-tapping if you
can ) and install a modern shimano BB cartridge.

There's no problem running a tap through to clean the threads out
as long as it's done properly, and also the state of bottom bracket
threads is a lot less critical when using cartridge bearings than CCB
bearings.

On 02/08/2011 19:25, Rob Morley wrote:
On Mon, 01 Aug 2011 19:31:34 +0100
Ron wrote:

Clean up the threads on the frame ( try to avoid re-tapping if you
can ) and install a modern shimano BB cartridge.

There's no problem running a tap through to clean the threads out
as long as it's done properly, and also the state of bottom bracket
threads is a lot less critical when using cartridge bearings than CCB
bearings.


Yes, but the 'properly' is the issue :-)

It's so easy to cross-thread the fine threads with the tap and totally
strip the BB housing. The LBS recently ruined a rather expensive frame
doing this...

After cleaning with a citrus cleaner, the thread ought to be basically
do-able by hand, with perhaps the odd tight spot.

If, after the first quarter-turn, you need a wrench, then *stop*, back
it out and start again!

--
Ron