Chainline/BB length estimation

Quoted post said:

Originally posted by Mseries
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

Quoted post said:

Originally posted by Mseries
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.

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-

sheldonbrown.combbsize.htmlOpen ↗

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:

parktool.comclg2.shtmlOpen ↗

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