Bottom bracket wont go.

lemmiwinks.au@gmail.com

I've just tried (and failed) to upgrade from a cup and cone bottom
bracket to the ubiquitous Shimano BB-UN54 cartridge bottom bracket.
In rec.bicycles.tech I've seen mention of ensuring that the faces of
the BB shell are true and I'm wondering if this could be part of my
problem.

It's a 68mm shell (I measured it at 68.09mm) and a 68mm cartridge but
they wouldn't go. I screwed the plastic cup in hand tight then began
tightening the BB itself from the drive side but it wouldn't go the
last 1-1.5mm. I removed everything and checked it over (measured
roughly, the distance from the inner face of the drive side to the
inner face of the plastic side came out more like 70mm than 68mm but
it was only a rough measurement and I assumed some crushability in the
plastic), the BB shell threads were clean, so I guessed this was how
it was meant to be. The second attempt caused the plastic cup to pop
out under the load, so something definitely isn't right, the cartridge
literally pushed it out the other side. As you'd expect the threads
on the plastic cup are pretty well rooted now, though probably still
serviceable since if my assumption is right it primarily supports the
BB within the shell.

I removed everything again then screwed the plastic cup back in and
noticed that there's a gap big enough to get my fingernail in at the
top when it's fully seated (and then some) at the bottom. I don't
know if was the case before I popped it or not, but I take this to
mean that the faces of the BB shell aren't true, though it could be
the plastic is stuffed.

So I guess I need to know; should I get the BB shell faced, is this
something the one and only LBS should be able to do (rough price
guide?) or will I just machine a bit off the inside of the plastic cup
so that the cartridge no longer drives it out and cut my losses? I'm
guessing I can't get a new plastic cup, so I won't even ask. I'm a
bit bemused, I bought a cheap VP components BB ages ago off eBay and
it went straight into one of my other bikes without even a hint of
trouble and it had a metal non drive side cup too (a plus in my "steel
is real" book), yet the Shimano...

Rory Williams

Some odd thoughts have you got the left and right sides correct? one of them has a left hand thread doesn't it

When I did one of mine ages ago I borrowed a tap from the LBS and ckeaned up the BB threads - and probably cut a few extra turns. How about counting the number of teeth on the 'carrier' and the BB and seeing if the BB has enough thread to accomodate it. you may be bottoming out.

RoryW

531Aussie

No, you've gotta put the drive side in first, then do it up very tight. The left 'cup' on a sealed BB is basically an 'afterthought'. When you put the left cup in, you've gotta make sure that's it's not so tight that it presses agaist the bearing seals and impedes the spin of the axle

However, it is slightly possible that you need the BB faced, but, mostly likely you've been doing it the wrong way 'round

PeteSig

<lemmiwinks.au@gmail.com> wrote:

> It's a 68mm shell (I measured it at 68.09mm) and a 68mm cartridge but
> they wouldn't go. I screwed the plastic cup in hand tight then began
> tightening the BB itself from the drive side but it wouldn't go the
> last 1-1.5mm...

Not the right method.

Put the full metal BB in first (from the drive side) then you tighten the
plastic 'cup' onto it from the left hand side. Depending on BB width it may
end up sticking out a bit, 3-5 threads, or recessed a bit. If you have the
right size BB it should only be protruding a very little bit (~1mm)

By tightening the plastic cup right in, you are putting it too far in, then
using the BB to push it back out again!!


--
Cheers
Peter

~~~ ~ _@
~~ ~ _- \,
~~ (*)/ (*)

lemmiwinks.au@gmail.com

On Mar 4, 11:40 pm, "PeteSig" <pete...@bigpond.com> wrote:
> <lemmiwinks...@gmail.com> wrote:
> > It's a 68mm shell (I measured it at 68.09mm) and a 68mm cartridge but
> > they wouldn't go. I screwed the plastic cup in hand tight then began
> > tightening the BB itself from the drive side but it wouldn't go the
> > last 1-1.5mm...
>
> Not the right method.
>
> Put the full metal BB in first (from the drive side) then you tighten the
> plastic 'cup' onto it from the left hand side. Depending on BB width it may
> end up sticking out a bit, 3-5 threads, or recessed a bit. If you have the
> right size BB it should only be protruding a very little bit (~1mm)
>
> By tightening the plastic cup right in, you are putting it too far in, then
> using the BB to push it back out again!!
>
> --
> Cheers
> Peter
>
> ~~~ ~ _@
> ~~ ~ _- \,
> ~~ (*)/ (*)

Well ain't I a dumbarse! Thanks for the corrections and suggestions
everyone. Ironically that's how I did it first but because I
encountered resistance I decided to do it the other way around since I
reasoned that the drive teeth on the plastic cup wouldn't bear much
load.

I'll have another crack at it tonight, hopefully whats left of the
plastic cup will suffice.

artemidorus

I'm not sure about this - I have always read that you tighten the fixed cup gently, just until it is snug against the shell, and then fit the left cup and torque it up to specification. I have broken the flange off a fixed cup through overtightening and can affirm that they are not made for high torque fitting.
I don't think that facing the shell is necessary for a single cartridge type BB. For the cup and cone BB to have worked, the shell faces couldn't have been too rough or out of square.

Joel Mayes

On 2008-03-05, artemidorus
<artemidorus.35s09c@no-mx.forums.cyclingforums.com> wrote:
>
> 531Aussie Wrote:
>> *No, you've gotta put the drive side in first, then do it up very
>> tight*. The left 'cup' on a sealed BB is basically an 'afterthought'.
>> When you put the left cup in, you've gotta make sure that's it's not
>> so tight that it presses agaist the bearing seals and impedes the
>> spin of the axle
>>
>> However, it is slightly possible that you need the BB faced, but,
>> mostly likely you've been doing it the wrong way 'round
> I'm not sure about this - I have always read that you tighten the
> fixed cup gently, just until it is snug against the shell, and then
> fit the left cup and torque it up to specification. I have broken the
> flange off a fixed cup through overtightening and can affirm that they
> are not made for high torque fitting. I don't think that facing the
> shell is necessary for a single cartridge type BB. For the cup and
> cone BB to have worked, the shell faces couldn't have been too rough
> or out of square.

It doesn't hurt to face the RH side of the BB shell if you're using a
cartridge BB, giving the flange a flat face to fasten against can only
help.

Cheers Joel


--
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joel@humanpowered.com.au | Affordable second hand bikes
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Tomasso

"PeteSig" <petesig@bigpond.com> wrote in message news:Aqbzj.22199$421.7563@news-server.bigpond.net.au...
>
> <lemmiwinks.au@gmail.com> wrote:
>
>> It's a 68mm shell (I measured it at 68.09mm) and a 68mm cartridge but
>> they wouldn't go. I screwed the plastic cup in hand tight then began
>> tightening the BB itself from the drive side but it wouldn't go the
>> last 1-1.5mm...
>
> Not the right method.
>
> Put the full metal BB in first (from the drive side) then you tighten the
> plastic 'cup' onto it from the left hand side. Depending on BB width it may
> end up sticking out a bit, 3-5 threads, or recessed a bit. If you have the
> right size BB it should only be protruding a very little bit (~1mm)
>
> By tightening the plastic cup right in, you are putting it too far in, then
> using the BB to push it back out again!!

Ditto.

Dave Hughes

On Tue, 04 Mar 2008 14:19:03 -0800, lemmiwinks.au wrote:

> I'll have another crack at it tonight, hopefully whats left of the
> plastic cup will suffice.

IIRC you're in Melbourne, otherwise I might be able to help with a spare
cup - I've got a few old ones I think. In any case, it could be worth a
visit to the LBS cap in hand to see if they've got one in the pile-o-crap.


--
Dave Hughes - dave@hired-goons.net
It's the twenty-first century, for Pete's sake. If you can't have a
flying car, you should at least be able to buy a sodding ray gun.
- Dan Rutter

lemmiwinks.au@gmail.com

On Mar 6, 10:57 am, Dave Hughes <spamb...@hired-goons.net> wrote:
> On Tue, 04 Mar 2008 14:19:03 -0800, lemmiwinks.au wrote:
> > I'll have another crack at it tonight, hopefully whats left of the
> > plastic cup will suffice.
>
> IIRC you're in Melbourne, otherwise I might be able to help with a spare
> cup - I've got a few old ones I think. In any case, it could be worth a
> visit to the LBS cap in hand to see if they've got one in the pile-o-crap.
>
> --
> Dave Hughes - d...@hired-goons.net
> It's the twenty-first century, for Pete's sake. If you can't have a
> flying car, you should at least be able to buy a sodding ray gun.
> - Dan Rutter

I'm north of Sydney, but thanks for the offer. Being a fussy bastard
I took a skim cut off the inside face that butts up against the BB in
an effort to get it to seat flush against the shell. I ended up
cracking the cup partly around it's circumference when I stupidly
tried to take it out without removing the BB first. It's still
serviceable though and I got it *nearly* flush, there's about a 2mm
gap at the bottom which is annoying but not really an issue.

It's installed and worked perfectly on the morning commute. But the
gmail address works if you want to get rid of an old plastic cup.
I've loctited the crank bolts, but I'm probably just fussy enough to
redo the whole thing if it means I end up with a non-cracked,
unstripped, flush mounted plastic cup ;-)

John Henderson

lemmiwinks.au@gmail.com wrote:

> I've loctited the crank bolts

Essential reading about square taper crank bolts:
http://draco.acs.uci.edu/rbfaq/FAQ/8f.11.html

Tightening torque - 25 to 32 ft-lbs:
http://www.parktool.com/repair/readhowto.asp?id=88

John

lemmiwinks.au@gmail.com

On Mar 6, 3:36 pm, John Henderson <jhenRemoveT...@talk21.com> wrote:
> lemmiwinks...@gmail.com wrote:
> > I've loctited the crank bolts
>
> Essential reading about square taper crank bolts:http://draco.acs.uci.edu/rbfaq/FAQ/8f.11.html

Oddly, I've never had trouble with crank bolts (or nuts in the case of
most cup and cone BB's) coming loose until I changed over to a
cartridge type BB. I'm sorry to say that my 8 speed has (slightly)
creaky cranks as a result of the bolts coming lose so I've taken to
applying a smidge of blue loctite to the bolts. I've not been game to
lubricate the taper, perhaps I'll give it a try next time.

John Henderson

lemmiwinks.au@gmail.com wrote:

> Oddly, I've never had trouble with crank bolts (or nuts in the
> case of most cup and cone BB's) coming loose until I changed
> over to a cartridge type BB. I'm sorry to say that my 8 speed
> has (slightly) creaky cranks as a result of the bolts coming
> lose so I've taken to applying a smidge of blue loctite to the
> bolts. I've not been game to lubricate the taper, perhaps
> I'll give it a try next time.

Likewise, I might try loctite on the bolt threads next time,
although I've never had one actually come undone enough for the
crank to become lose on the crank axle itself.

John

lemmiwinks.au@gmail.com

On Mar 7, 12:20 pm, John Henderson <jhenRemoveT...@talk21.com> wrote:
> lemmiwinks...@gmail.com wrote:
> > Oddly, I've never had trouble with crank bolts (or nuts in the
> > case of most cup and cone BB's) coming loose until I changed
> > over to a cartridge type BB. I'm sorry to say that my 8 speed
> > has (slightly) creaky cranks as a result of the bolts coming
> > lose so I've taken to applying a smidge of blue loctite to the
> > bolts. I've not been game to lubricate the taper, perhaps
> > I'll give it a try next time.
>
> Likewise, I might try loctite on the bolt threads next time,
> although I've never had one actually come undone enough for the
> crank to become lose on the crank axle itself.
>
> John

Mine were never flapping around in the breeze, but an intermittent
creaking/clicking noise developed which I realised from reading here
and RBT was coming from loose cranks and when I checked the bolts this
was confirmed. The cranks on my hub gear bike now generally only
creak when I roll out of a driveway or similar while standing on the
pedals with the cranks horizontal, they're tight enough that pedaling
doesn't cause any noise. It still irritates me to know I've damaged
them through my carelessness though.