Chainline/BB length estimation

Mseries said:

I have acquired a old Deore triple chainset (110/74mm PCD) which will be
ideal for converting my tourer to a triple. I can't climb but love the
hills, the challenge, the scenary and the descents. My frame is a 1986
Reynolds 531 tourer with 68mm BB shell. I can calculate the required
chainline from the rear hub but how does this tell me what length BB I
need. (The Sugino double that is currently fitted has a 118mm BB)

http://www.parktool.com/repair_help/clg2.shtml

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Mseries said:

I have acquired a old Deore triple chainset (110/74mm PCD) which will be
ideal for converting my tourer to a triple. I can't climb but love the
hills, the challenge, the scenary and the descents. My frame is a 1986
Reynolds 531 tourer with 68mm BB shell. I can calculate the required
chainline from the rear hub but how does this tell me what length BB I
need. (The Sugino double that is currently fitted has a 118mm BB)

Barnetts Chapter 27 should also help you choose the proper BB size.

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On Sat, 8 May 2004 20:45:52 +0100, "MSeries" <[email hidden]>

Quoted message said:

I have acquired a old Deore triple chainset (110/74mm PCD) which will be
ideal for converting my tourer to a triple. I can't climb but love the
hills, the challenge, the scenary and the descents. My frame is a 1986
Reynolds 531 tourer with 68mm BB shell. I can calculate the required
chainline from the rear hub but how does this tell me what length BB I need.
(The Sugino double that is currently fitted has a 118mm BB)

You might look here-

http://www.sheldonbrown.com/bbsize.html

The actual model number of your cranks will be on the inside
somewhere.

I'd simply put the cranks on your present BB and see how the chainline
looks- someone posted some good links for checking this.

For what it's worth, I've had two older 110/74 cranks, one SR and one
Shimano, and both used a 122mm BB.

MSeries said:

I have acquired a old Deore triple chainset (110/74mm PCD) which will
be ideal for converting my tourer to a triple. I can't climb but love
the hills, the challenge, the scenary and the descents. My frame is a
1986 Reynolds 531 tourer with 68mm BB shell. I can calculate the
required chainline from the rear hub but how does this tell me what
length BB I need. (The Sugino double that is currently fitted has a
118mm BB)

122.5mm I managed to find the BB that was fitted when I removed the old
chainset from the bike to which it was originally fitted. Tried the parts in
my tourer and bobs yer uncle. The old BB is in reasonable condition too,
it'll do to get me going, probably last the summer.

Quoted message said:

Mseries said:

I have acquired a old Deore triple chainset (110/74mm PCD) which will be
ideal for converting my tourer to a triple. I can't climb but love the
hills, the challenge, the scenary and the descents. My frame is a 1986
Reynolds 531 tourer with 68mm BB shell. I can calculate the required
chainline from the rear hub but how does this tell me what length BB I
need. (The Sugino double that is currently fitted has a 118mm BB)

daveornee said:

http://www.parktool.com/repair_help/clg2.shtml

If he has the original Deore M730 crank, it ideally takes an
asymmetric spindle, D3L.

If he wants to use a lesser 'sealed' type symmetric BB,
probably start with a 122.5.
(That's theoretically a touch (1mm) on the short side.)

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