Bottom Bracket installation question

Someone claiming to be Me said:

Hi I have a three year old Shimano UN91 BB and it doesn't seem to be screwing into my frame
very easily.

I've tried 2 other Shimano BBs and they both go in by hand.

But neither side of this one is easy to put more than a thread or two in by any means.

I'm afraid to put a wrench on it and give it some torque for fear of damaging my frame.

I was wondering if perhaps this could be an Italian thread pitch instead of a standard English.

Does anyone know if Shimano makes Italian threaded stuff?

They do, but Italian is substantially larger than ISO standard, so I wouldn't expect it to screw in
at all. Also, Italian stuff has both sides threaded right hand (wrong way for the right side.)

Actually, the thread _pitch_ is the same for both, 24 tpi, but that's not a particularly useful
fact, since they are absolutely _not_ interchangeable.

Quoted message said:

Also, how do I tell from looking at it if I have an italian or english bottom bracket?

Shimano Italian BBs will have the number "70" somewhere (that's the shell width in mm.) Standard BBs
will be marked 68 or occasionally 73 for oversized MTB applications.

I'm guessing your UN91 has damaged threads. Grease it up and try a bit harder to screw it in. If
you have a steel frame, it's very unlikely the aluminum retaining rings could do any important
damage to the threads in the bottom bracket shell. If it's an aluminum frame, however, you need to
be extra careful.

There's a detailed chart showing the various bottom bracket specs in my Bicycle Glossary, see:
sheldonbrown.comglossaryOpen ↗

Sheldon "1.37 x 24" Brown +--------------------------------------------------+
| My son George has written a Trombone Concerto | You can hear it at sheldonbrown.commp3Open ↗ |
+--------------------------------------------------+ Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041 harriscyclery.comharriscyclery.comOpen ↗ Hard-to-find parts shipped Worldwide
captainbike.comcaptainbike.comOpen ↗ sheldonbrown.comsheldonbrown.comOpen ↗

Thanks for the speedy reply sheldon...

Just checkd the BB and it has BC 1.37 stamped on the side so at least I know its an ISO English
thread. Yea!

So that means I'm working with compatible stuff and only need to get it in.

I got another question if you dont mind...

Its a Ti frame and I have 2 other BBs that slide in by hand and no visible sign of gunk in
the BB shell.

But I've been trying my best to clean up the threads on the BB itself. Any suggestions on how to
really get down in the threads and get out 3 years worth of locktight/grease/and clay?

I've tried using a knife to "chase" round the threads and pry up some of the gunk as well as
degreaser but I can still see some gunk in the grooves.

Is there a tool for such things?

I know that there will be a time when I just gotta put my BB tool and wrench on it and turn but I
want to lessen any chance of damaging my Ti frame as dont know if I could have the BB shell repaired
if I do any damage...

-cheers

"Sheldon Brown" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Someone claiming to be Me said:

Hi I have a three year old Shimano UN91 BB and it doesn't seem to be screwing into my frame very
easily.

I've tried 2 other Shimano BBs and they both go in by hand.

But neither side of this one is easy to put more than a thread or two in

by

Quoted message said:

Quoted message said:

any means.

I'm afraid to put a wrench on it and give it some torque for fear of damaging my frame.

I was wondering if perhaps this could be an Italian thread pitch instead

of

Quoted message said:

Quoted message said:

a standard English.

Does anyone know if Shimano makes Italian threaded stuff?

They do, but Italian is substantially larger than ISO standard, so I wouldn't expect it to screw
in at all. Also, Italian stuff has both sides threaded right hand (wrong way for the right side.)

Actually, the thread _pitch_ is the same for both, 24 tpi, but that's not a particularly useful
fact, since they are absolutely _not_ interchangeable.

Quoted message said:

Also, how do I tell from looking at it if I have an italian or english bottom bracket?

Shimano Italian BBs will have the number "70" somewhere (that's the shell width in mm.) Standard
BBs will be marked 68 or occasionally 73 for oversized MTB applications.

I'm guessing your UN91 has damaged threads. Grease it up and try a bit harder to screw it in. If
you have a steel frame, it's very unlikely the aluminum retaining rings could do any important
damage to the threads in the bottom bracket shell. If it's an aluminum frame, however, you need to
be extra careful.

There's a detailed chart showing the various bottom bracket specs in my Bicycle Glossary, see:
sheldonbrown.comglossaryOpen ↗

Sheldon "1.37 x 24" Brown +--------------------------------------------------+
| My son George has written a Trombone Concerto | You can hear it at
| sheldonbrown.commp3Open ↗ |
+--------------------------------------------------+ Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041 harriscyclery.comharriscyclery.comOpen ↗ Hard-to-find parts shipped Worldwide
captainbike.comcaptainbike.comOpen ↗ sheldonbrown.comsheldonbrown.comOpen ↗

yes there are thread files around but l am in australia so l cant be much help as to where you would
get one but just an idea you don't have an old bike laying around somewhere, or is there one on a
junk pile, or in a creek if you can lay your hands on one then screw your BB into that first, if you
stuff the BB or the frame who cares and you are up for a new BB, but at least you wont have damaged
your good frame if it is tight, turn it like a tape half a turn in then back it off to let any [censored]
fall out then in another half turn

A brass-bristle "toothbrush" works great.

"stu" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

yes there are thread files around but l am in australia so l cant be much help as to where you
would get one but just an idea you don't have an old bike laying around somewhere, or is there
one on a junk pile, or in a creek if you can lay your hands on one then screw your BB into that
first, if

you

Quoted message said:

stuff the BB or the frame who cares and you are up for a new BB, but at least you wont have
damaged your good frame if it is tight, turn it like a tape half a turn in then back it off to let
any [censored] fall out then in another half turn

Me <[email hidden]> wrote:

: Its a Ti frame and I have 2 other BBs that slide in by hand and no visible sign of gunk in the
: BB shell.

: But I've been trying my best to clean up the threads on the BB itself. Any suggestions on how to
: really get down in the threads and get out 3 years worth of locktight/grease/and clay?

: I've tried using a knife to "chase" round the threads and pry up some of the gunk as well as
: degreaser but I can still see some gunk in the grooves.

: Is there a tool for such things?

: I know that there will be a time when I just gotta put my BB tool and wrench on it and turn but I
: want to lessen any chance of damaging my Ti frame as dont know if I could have the BB shell
: repaired if I do any damage...

A wire brush is good for cleaning threads. A rotary wire brush is even better. Just make sure you
aren't trying to screw in the wrong threads, ie, left hand threads into the left side of the bike or
vice versa. And, I hope you are going to use anti-sieze compound!

Cheerz, Lynzz

Me said:

Just checkd the BB and it has BC 1.37 stamped on the side so at least I know its an ISO English
thread. Yea!

So that means I'm working with compatible stuff and only need to get it in.

I got another question if you dont mind...

Its a Ti frame and I have 2 other BBs that slide in by hand and no visible sign of gunk in the
BB shell.

But I've been trying my best to clean up the threads on the BB itself. Any suggestions on how to
really get down in the threads and get out 3 years worth of locktight/grease/and clay?

I use a cylindrical rotary wire brush. This is a standard hardware store item. I use one that's
about an inch in diameter, 2 or 3 inches long. I chuck it into a cheap old high speed electric
drill. Works really well.

Sheldon "I Learned That From Francis Bolag" Brown
+-------------------------------------------------+
| Live near Boston? Want to learn to play jazz? |
| See my jazz site: artsforall.comartsforall.comOpen ↗ |
+-------------------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone
617-244-9772 FAX 617-244-1041 harriscyclery.comharriscyclery.comOpen ↗ Hard-to-find parts shipped Worldwide
captainbike.comcaptainbike.comOpen ↗ sheldonbrown.comsheldonbrown.comOpen ↗

Capt Bike-<< Also, Italian stuff has both sides threaded right hand (wrong way for the right side.)

Tried to come up with something 'pithy' for this but just couldn't too much a-goin' on these
days...plus 38 inches of snow yesterday....

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 vecchios.comvecchios.comOpen ↗ "Ruote convenzionali costruite eccezionalmente bene"

In article <[email hidden]>, [email hidden] (Qui si parla

Campagnolo) said:

Capt Bike-<< Also, Italian stuff has both sides threaded right hand (wrong way for the
right side.)

Tried to come up with something 'pithy' for this but just couldn't too much a-goin' on these
days...plus 38 inches of snow yesterday....

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302
(303)440-3535 vecchios.comvecchios.comOpen ↗ "Ruote convenzionali costruite eccezionalmente bene"

What??

Isn¹t that just flurries to you guys?

Just put the cross country skiis away til next year.

HAND

--
³Freedom Is a Light for Which Many Have Died in Darkness³

- Tomb of the unknown - American Revolution

Qui si parla Campagnolo <[email hidden]> wrote:
: They say biggest snow amount in the time frame for 20 years...

yea, up until this point i had been pretty impressed with colorado's winter. on the up side it's
above freezing starting tomorrow. i'm banking on it melting the driveway before the food runs out.
--
david reuteler [email hidden]

Quoted message said:

Capt Bike-

who doesn't bait and therefore must be tongue-in-cheek today, wrote: << Also, Italian stuff has both

Quoted message said:

sides threaded right hand (wrong way for the right side.)

"Qui si parla Campagnolo" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Tried to come up with something 'pithy' for this but just couldn't too

much

Quoted message said:

a-goin' on these days...plus 38 inches of snow yesterday....

May I try then? In theory the Italian isn't optimal but in practice it works just fine. We LokTite
right side Italian cups and torque adequately as do almost all shops who sell Italian frames. Since
there are not many cases of wandering Italian cups* there is not an actual probelem, just a
theoretical one!

*There were once cheap poorly assembled French and Italian threaded cups in great numbers and those
did unscrew frequently. Product quality of right side thread frames and cups is generally better
now. Assembly quality is very much improved now that there are not $69 Italian threaded bicycles. If
there _were_ a problem I would welcome discussion of it!

--
Andrew Muzi yellowjersey.orgyellowjersey.orgOpen ↗ Open every day since 1 April 1971