Switching Parts Between Bikes - Bottom Bracket in Question



R

Rosco

Guest
I'm looking to move some ~15 year old 7 speed Dura-Ace parts
over to a different bike. The "donor bike" seems to have an
Italian threaded bottom bracket (Shimano BB-7400 36x24T)
whereas the "recipient bike" is English threaded. The
Shimano square taper double crankset is still in very good
shape, so I'd like to save it.

Can someone confirm that the BB-7400 36x24T is indeed
Italian? Secondly, what English threaded bottom bracket
would folks suggest? I'm looking for something of only
decent quality. After about a year, the parts will return to
their original bike (assuming I can then afford a new
Campagnolo parts set).
 
F

Frank121

Guest
36x24 is Italian...think of the stereotypical figures
of the Italian movie starlets of the past as in 36-24-
36 to remember.

"rosco" <reverse-the-following"ocsor_g"@hotmail.com> wrote
in message news:D[email protected]
hlink.net...
> I'm looking to move some ~15 year old 7 speed Dura-Ace
> parts over to a different bike. The "donor bike" seems to
> have an Italian threaded bottom bracket (Shimano BB-7400
> 36x24T) whereas the "recipient bike" is English threaded.
> The Shimano square taper double crankset is still in very
> good shape, so I'd like to save it.
>
> Can someone confirm that the BB-7400 36x24T is indeed
> Italian? Secondly, what English threaded bottom bracket
> would folks suggest? I'm looking for something of only
> decent quality. After about a year, the parts will
return
> to their original bike (assuming I can then afford a new
> Campagnolo parts set).
 
S

Sheldon Brown

Guest
rosco wrote:
> I'm looking to move some ~15 year old 7 speed Dura-Ace
> parts over to a different bike. The "donor bike" seems to
> have an Italian threaded bottom bracket (Shimano BB-7400
> 36x24T) whereas the "recipient bike" is English threaded.
> The Shimano square taper double crankset is still in very
> good shape, so I'd like to save it.
>
> Can someone confirm that the BB-7400 36x24T is indeed
> Italian?

BB-7400 is Dura-Ace 1990-95.

36x24t is Italian.

See: http://sheldonbrown.com/bbsize.html#dura

> what English threaded bottom bracket would folks suggest?
> I'm looking for something of only decent quality. After
> about a year, the parts will return to their original bike
> (assuming I can then afford a new Campagnolo parts

I'd recommend a UN53 or UN73 68 x 115.

See: http://harriscyclery.net/site/page.cfm?PageID=49&Cat-
egory=1050

According to my Bottom Bracket Size database
(http://sheldonbrown.com/bbsize.html#dura) this crank
originally used a 112 asymmetrical spindle for use with a
68 mm BB, but with modern symmetrical bbs you want to go a
bit longer.

Sheldon "We've Got 'Em" Brown +----------------------------------------------------
+
| A little inaccuracy sometimes saves tons of |
| explanation. --H.H.Munro ("Saki")(1870-1916) |
+----------------------------------------------------+
Harris Cyclery, West Newton, Massachusetts Phone 617-244-
9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find
parts shipped Worldwide http://captainbike.com
http://sheldonbrown.com
 
R

Rosco

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

>
> > what English threaded bottom bracket would folks
> > suggest? I'm looking
for
> > something of only decent quality. After about a year,
> > the parts will
return
> > to their original bike (assuming I can then afford a new
> > Campagnolo
parts
>
> I'd recommend a UN53 or UN73 68 x 115.
>
> See: http://harriscyclery.net/site/page.cfm?PageID=49&Cat-
> egory=1050
>
> According to my Bottom Bracket Size database
> (http://sheldonbrown.com/bbsize.html#dura) this crank
> originally used a 112 asymmetrical spindle for use with a
> 68 mm BB, but with modern symmetrical bbs you want to go a
> bit longer.
>

One detail I forgot to mention...

The donor rear wheel is 126mm spaced (w/ freewheel not
cassette) whereas the recipient rear spacing is 130mm. I
figured by changing the axle and adding some 2mm spacers to
both sides I can make this work. Does this sound like a good
approach given the relatively short time it will remain on
the recipient bike?

Will this approach dictate a slightly shorter bottom bracket
spindle for the sake of chain line?
 
A

A Muzi

Guest
rosco wrote:

> I'm looking to move some ~15 year old 7 speed Dura-Ace
> parts over to a different bike. The "donor bike" seems to
> have an Italian threaded bottom bracket (Shimano BB-7400
> 36x24T) whereas the "recipient bike" is English threaded.
> The Shimano square taper double crankset is still in very
> good shape, so I'd like to save it.
>
> Can someone confirm that the BB-7400 36x24T is indeed
> Italian? Secondly, what English threaded bottom bracket
> would folks suggest? I'm looking for something of only
> decent quality. After about a year, the parts will return
> to their original bike (assuming I can then afford a new
> Campagnolo parts set).
>
>
Yes 36mm is Italian.

That crank uses the same effective spindle dimensions as
the classic Campagnolo Record 1046 and Nuovo Record 1046a.
A score of other manufacturers produced similar dimension
units but AFAIK only Phil Wood is currently in production.
Still, since that was such a popular size for such a long
time, compatible BBs abound across a wide range of price
and quality.

--
Andrew Muzi www.yellowjersey.org Open every day since 1
April, 1971
 
Q

Qui Si Parla Ca

Guest
rosco-<< Can someone confirm that the BB-7400 36x24T is
indeed Italian?
>><BR><BR>
<< Secondly, what English threaded bottom bracket would
folks suggest? >><BR><BR>

A 7400 in english threading?

Or a UN-72 in 113mm length and english threading.

Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St.
Boulder, CO, 80302
(303)440-3535 http://www.vecchios.com "Ruote convenzionali
costruite eccezionalmente bene"
 
S

Sheldon Brown

Guest
rosco asked:

>>> what English threaded bottom bracket would folks
>>> suggest? I'm looking for something of only decent
>>> quality. After about a year, the parts will return to
>>> their original bike (assuming I can then afford a new
>>> Campagnolo parts

I replied:

>>I'd recommend a UN53 or UN73 68 x 115.
>>
>>See: http://harriscyclery.net/site/page.cfm?PageID=49&Cat-
>>egory=1050
>>
>>According to my Bottom Bracket Size database
>>(http://sheldonbrown.com/bbsize.html#dura) this crank
>>originally used a 112 asymmetrical spindle for use with a
>>68 mm BB, but with modern symmetrical bbs you want to go a
>>bit longer.

On redirect, rosco asked:

> One detail I forgot to mention...
>
> The donor rear wheel is 126mm spaced (w/ freewheel not
> cassette) whereas the recipient rear spacing is 130mm. I
> figured by changing the axle and adding some 2mm spacers
> to both sides I can make this work. Does this sound like a
> good approach given the relatively short time it will
> remain on the recipient bike?
>
> Will this approach dictate a slightly shorter bottom
> bracket spindle for the sake of chain line?

Derailer chainline is not a high-precision matter, unless
you have indexed front shifting. A 113 would probably work
too, but you might run into chanstay clearance issues or
front derailer travel issues.

If it were mine, I'd try a 113 with the awareness that it
might be too short. However, if I had to actually _buy_ a BB
without a trial fit, I'd go with the 115, which I'm sure
will work.

For road gearing, I prefer to bias the front chainline
inward to favor the big ring, as long as that doesn't cause
clearance or shifting issues. This approach allows efficient
use of more rear sprockets with the big ring, at the cost of
creating problems if you run the small chainring with the
smaller rear sprockets. Since I generally avoid those
combinations, this is a good tradeoff for me.

Sheldon "Not An Exact Science" Brown +------------------------------------------------------
---------+
| The poet Henry O'Meara (1848-1904) was my great-
| grandfather | I've put his book "Ballads of America and
| Other Poems" | on the Web at:
| http://sheldonbrown.com/omeara |
+-----------------------------------------------------------
----+ Harris Cyclery, West Newton, Massachusetts Phone 617-244-
9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find
parts shipped Worldwide http://captainbike.com
http://sheldonbrown.com
 
A

A Muzi

Guest
> rosco-<< Can someone confirm that the BB-7400 36x24T is
> indeed Italian? << Secondly, what English threaded bottom
> bracket would folks suggest? >><BR><BR>

Qui si parla Campagnolo wrote:
> A 7400 in english threading? Or a UN-72 in 113mm length
> and english threading.

Maybe, but only because a standard taper crank ( The BB-7400
is 100% interchangeable with Nuovo Record 1046a) will only
go halfway up the taper of a UN-72.

An ACH 115 is a much closer fit. & left arm sits out a bit.

The BB-7400 spindle is asymmetric, so a simple "overall
length" analysis is wanting for accuracy.
--
Andrew Muzi www.yellowjersey.org Open every day since 1
April, 1971
 
R

Rosco

Guest
"A Muzi" <[email protected]> wrote in message
news:[email protected]...
> > rosco-<< Can someone confirm that the BB-7400 36x24T is
> > indeed Italian? << Secondly, what English threaded
> > bottom bracket would folks suggest? >><BR><BR>
>
> Qui si parla Campagnolo wrote:
> > A 7400 in english threading? Or a UN-72 in 113mm length
> > and english threading.
>
> Maybe, but only because a standard taper crank ( The BB-
> 7400 is 100% interchangeable with Nuovo Record 1046a) will
> only go halfway up the taper of a UN-72.
>
> An ACH 115 is a much closer fit. & left arm sits out a
> bit.
>
> The BB-7400 spindle is asymmetric, so a simple "overall
> length" analysis is wanting for accuracy.
> --
> Andrew Muzi www.yellowjersey.org Open every day since 1
> April, 1971
>

I got a UN52 in 113mm length at a LBS. At the shop, the FC-
7400 crank arm seemed to fit similar to the BB-7400 it came
off of (it slid on with hand pressure about 7/8 of the way
down the taper of the crank arm). Installed the UN52 on the
bike, and installed the drive side crank arm (torqued to
about 20-25 ft pd). The crank arm was very much fully on
the taper at this point. The resulting chainline seemed
pretty close to spot-on (43.5mm). The LBS consulted
Sutherlands Repair Manual, and concluded that the FC-7400
was JIS and Campagnolo was the next best fit. However,
Sutherlands gave no useful information on how to translate
from the BB-7400 to a UN series cartridge sealed bearing
based bottom bracket.
 
A

A Muzi

Guest
> "A Muzi" <[email protected]> wrote in message
> news:[email protected]...
-blah blah blah>-

rosco wrote:
> I got a UN52 in 113mm length at a LBS. At the shop, the
> FC-7400 crank arm seemed to fit similar to the BB-7400 it
> came off of (it slid on with hand pressure about 7/8 of
> the way down the taper of the crank arm). Installed the
> UN52 on the bike, and installed the drive side crank arm
> (torqued to about 20-25 ft pd). The crank arm was very
> much fully on the taper at this point. The resulting
> chainline seemed pretty close to spot-on (43.5mm). The LBS
> consulted Sutherlands Repair Manual, and concluded that
> the FC-7400 was JIS and Campagnolo was the next best fit.
> However, Sutherlands gave no useful information on how to
> translate from the BB-7400 to a UN series cartridge sealed
> bearing based bottom bracket.

I actually dug up an NOS 7400 crank and looked at the actual
spindle penetration.
http://www.yellowjersey.org/photosfromthepast/7400_2.JPG

(method: both were simply pressed firmly by hand, not
properly torqued, the arm is brand new.)

The difference from Campagnolo to Shimano spindle taper is
much less than I remembered. Probably either would be OK
given the right length and they're about the same price. I
stand corrected.

--
Andrew Muzi www.yellowjersey.org Open every day since 1
April, 1971
 
R

Rosco

Guest
"rosco" <reverse-the-following"ocsor_g"@hotmail.com> wrote in message
news:D[email protected]...
> I'm looking to move some ~15 year old 7 speed Dura-Ace
> parts over to a different bike. The "donor bike" seems to
> have an Italian threaded bottom bracket (Shimano BB-7400
> 36x24T) whereas the "recipient bike" is English threaded.
> The Shimano square taper double crankset is still in very
> good shape, so I'd like to save it.
>
> Can someone confirm that the BB-7400 36x24T is indeed
> Italian? Secondly, what English threaded bottom bracket
> would folks suggest? I'm looking for something of only
> decent quality. After about a year, the parts will
return
> to their original bike (assuming I can then afford a new
> Campagnolo parts set).
>
>

Thanks to Andrew, Sheldon and Peter for your wonderful
assistance!