UN73

I have UN-73's on two of my six bikes right now and have
also noticed that the left cup doesn't screw in fully. But
they've worked fine for several thousand miles with
nothing loosening or making noise. So I'd say it's nothing
to worry about.

Mike Yankee

(Address is munged to thwart spammers. To reply, delete
everything after "com".)

Steve said:

I installed a Shimano UN91 b-bracket on a Ti Lemond a year
ago and have just replaced it (pitting/creaking, etc...)
with a UN73. It's what the shop had.

The UN91 was a "thread in from the left" which was no big
deal. My 2 other road bikes use UN72's, so I'm familar
with the installations.

The UN73 has a much wider (greater threads) left cup, that
will not screw
in/set in to the bottom bracket shell as far as the UN91,
nor will it set in as far as the UN72's on my other 2
bikes. It has about 10mm or so of thread on the outside
of the shell, where as the UN72's were flush to the
shell.

The 73 is seemingly is a tight as it needs to be - I've
used torque wrenches, setting to the pressure as
recommended on the Park Tool site.

My question is, is having this much thread exposed normal
?. The 73 does use a cup that has a good bit more threads
then the UN72's I'm familiar with.

FWIW, the crank arms are equal distance from the
chainstays (or at least within a few mm of each other) so
all looks kosher and the cranks feels solid with no play.

I wonder if you might have accidentally gotten a BB intended
for an over sized (73 mm) bottom bracket shell, rather than
the much more common 68 mm size.

It's normal for a few threads to be visible on the left
side, but if there are a lot, it might be worth re-checking.

It was a bit boneheaded of Shimano to designate the model
"UN-73" when "73" is also one of the dimensions.

Reminds me of the scale-focussing Olympus camera that had
distance markings of 2.8, 4, 5.6, 8, 11 and infinity, all
too easily confused with the f-stop control. (Going from
memory here, might not have been all of those numbers...)

Sheldon "Oops!" Brown +----------------------------------------------------
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+----------------------------------------------------+
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Quoted message said:

Reminds me of the scale-focussing Olympus camera that had
distance markings of 2.8, 4, 5.6, 8, 11 and infinity, all
too easily confused with the f-stop control. (Going from
memory here, might not have been all of those numbers...)

Hehe, that probably wouldn't be coincidence if they had all
5 of those... maybe they intended it as an easter egg 😉

--
Phil, Squid-in-Training

sbm-<< The UN73 has a much wider (greater threads) left cup,
that will not screw
in/set in to the bottom bracket shell as far as the UN91,

Quoted message said:

Quoted message said:

<BR><BR>

They sold ya a BB for a 73mm shell, not a 68mm shell..

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

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

m15.aol.com...

Quoted message said:

sbm-<< The UN73 has a much wider (greater threads) left
cup, that will not screw
in/set in to the bottom bracket shell as far as the UN91,

Quoted message said:

Quoted message said:

<BR><BR>

They sold ya a BB for a 73mm shell, not a 68mm shell..

Peter Chisholm

Yep, they sure did (LBS).

Question is, does it matter, except for appearences.

My guess would be that it'll work just fine

SB

On Wed, 28 Apr 2004 16:14:22 GMT, "Steve" <[email hidden]>

Quoted message said:

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

m15.aol.com...

Quoted message said:

sbm-<< The UN73 has a much wider (greater threads) left
cup, that will not screw
in/set in to the bottom bracket shell as far as the UN91,

Quoted message said:

><BR><BR>

They sold ya a BB for a 73mm shell, not a 68mm shell..

Peter Chisholm

Yep, they sure did (LBS).

Question is, does it matter, except for appearences.

My guess would be that it'll work just fine

SB

When I installed a 68 width in a 73 BB shell, the cranks
were offset to the right. Along with the left cup going in a
bit far, this is what made me realize what I had done.

Technically it would matter, Your cranks will be offset 2.5
mm to the left. The right cup will stop on the face of a 68
mm shell, but it is designed to be 2.5 mm further out.

As to whether a chainline 2.5 mm off is bothersome to
you....

"Dan Daniel" <[email hidden]> wrote in message

Quoted message said:

When I installed a 68 width in a 73 BB shell, the cranks
were offset to the right. Along with the left cup going in
a bit far, this is what made me realize what I had done.

Technically it would matter, Your cranks will be offset
2.5 mm to the left. The right cup will stop on the face
of a 68 mm shell, but it is designed to be 2.5 mm
further out.

As to whether a chainline 2.5 mm off is bothersome
to you....

The spindle length is the same, 68 or 73 (or so I believe)
and the crank arms are almost equal distance from the
chainstays. The left cup just sticks out further.

Everything about the b-bracket seems identical to a spare
UN72/115/68 I have in a drawer (except the spindle length,
of course), just the left side cup is longer.

Being that the box says "68" and had no crank bolts, I
suspect this is an older bracket (NOS) that was sitting
in the drawer at the LBS and possibly has been returned
on a prior occasion, with some mix and (no) matching
having occurred.

Whatever, it's being removed and returned tomorrow.

SB