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Switching Parts Between Bikes - Bottom Bracket in Question



 
 
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  #1  
Old March 17th 04, 04:49 AM
rosco
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Default Switching Parts Between Bikes - Bottom Bracket in Question

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).


Ads
  #2  
Old March 17th 04, 05:17 AM
frank121
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Default Switching Parts Between Bikes - Bottom Bracket in Question

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


"rosco" wrote in message
news
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).




  #3  
Old March 17th 04, 05:22 AM
Sheldon Brown
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Default Switching Parts Between Bikes - Bottom Bracket in Question

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.c...&Category=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

  #4  
Old March 17th 04, 05:49 AM
rosco
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Default Switching Parts Between Bikes - Bottom Bracket in Question


"Sheldon Brown" wrote in message
...


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.c...&Category=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?


  #5  
Old March 17th 04, 07:42 AM
A Muzi
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Posts: n/a
Default Switching Parts Between Bikes - Bottom Bracket in Question

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

  #6  
Old March 17th 04, 03:18 PM
Qui si parla Campagnolo
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Default Switching Parts Between Bikes - Bottom Bracket in Question

rosco- Can someone confirm that the BB-7400 36x24T is indeed Italian?
BRBR

Secondly,
what English threaded bottom bracket would folks suggest? BRBR

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"
  #7  
Old March 17th 04, 06:00 PM
Sheldon Brown
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Default Switching Parts Between Bikes - Bottom Bracket in Question

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.c...&Category=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

  #8  
Old March 18th 04, 06:08 AM
A Muzi
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Default Switching Parts Between Bikes - Bottom Bracket in Question

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


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

  #9  
Old March 18th 04, 06:54 AM
rosco
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Default Switching Parts Between Bikes - Bottom Bracket in Question

"A Muzi" wrote in message
...
rosco- Can someone confirm that the BB-7400 36x24T is indeed Italian?
Secondly,
what English threaded bottom bracket would folks suggest? BRBR


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.


  #10  
Old March 18th 04, 07:59 AM
A Muzi
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Default Switching Parts Between Bikes - Bottom Bracket in Question

"A Muzi" wrote in message
...

-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/photosfr...ast/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

 




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