Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 03-29-11, 08:10 PM   #1
nepg
Senior Member
Thread Starter
 
Join Date: Aug 2008
Location: Kansas City, MO
Bikes:
Posts: 101
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Being cautious...crankset-bottom bracket compatibility question.

I'm turning my 80's road bike into a singlespeed (mostly for maintenance benefits and discomfort of downtube shifters). I have a new crankset, but need to get a bottom bracket. The problem I've had with bottom brackets is that the bike frame is an Italian thread, and my options for square-tapered bottom brackets is extremely limited.

The real question:

The crankset specs say it accepts 108mm bottom brackets. The closest bottom brackets available are 107 and 110. Which one is the way to go? Neither?

Thanks.
nepg is offline   Reply With Quote
Old 03-29-11, 08:17 PM   #2
reptilezs
Senior Member
 
Join Date: Sep 2004
Location: boston, ma
Bikes:
Posts: 2,852
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
if the 108 spindle gives you the ideal chainline then i would get the 107
reptilezs is offline   Reply With Quote
Old 03-29-11, 08:23 PM   #3
Mr. Fly
Senior Member
 
Mr. Fly's Avatar
 
Join Date: Jan 2007
Location: Silicon Valley, CA.
Bikes:
Posts: 662
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by nepg View Post
The problem I've had with bottom brackets is that the bike frame is an Italian thread, and my options for square-tapered bottom brackets is extremely limited.
...

The crankset specs say it accepts 108mm bottom brackets. The closest bottom brackets available are 107 and 110. Which one is the way to go?
BB spindle lengths are specified by the factory with a particular chainline in mind. That also means it is matched to the intended use of the crank. To answer your question, you need to clarify if you're converting a double to a single because that may mean you need to adjust from the factory spec to get that one chainring lined up. If your new crank is designed as a single, then I would go with 107mm, assuming acceptable clearance, because your chainline is then off by only 0.5mm. Using the 110mm spindle will throw off the chainline by 1.5mm (half of 3mm).

In addition to the spindle length and BB threading, do you know if you also have the correct spindle taper? There's JIS and ISO and although they may be cross-compatible (to some extent), using one for the other will definitely impact your chainline.
Mr. Fly is offline   Reply With Quote
Old 03-29-11, 08:33 PM   #4
fietsbob 
coprolite
 
fietsbob's Avatar
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Bikes: 7
Posts: 22,040
Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 1096 Post(s)
.
Quote:
I have a new crankset, but need to get a bottom bracket.
+1 , ... so is it a track/single speed crank?

using 1 out of a double , the chain line runs thru the spider arm. so both chainrings are off that line .

but no clue what real chaineline you got.. lay a yardstick on the cog and see.
fietsbob is offline   Reply With Quote
Old 03-30-11, 10:41 AM   #5
nepg
Senior Member
Thread Starter
 
Join Date: Aug 2008
Location: Kansas City, MO
Bikes:
Posts: 101
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Yup, it's a singlespeed crank.
nepg is offline   Reply With Quote
Old 03-30-11, 12:19 PM   #6
JohnDThompson 
Old fart
 
JohnDThompson's Avatar
 
Join Date: Nov 2004
Location: Appleton WI
Bikes: Several, mostly not name brands.
Posts: 16,757
Mentioned: 12 Post(s)
Tagged: 0 Thread(s)
Quoted: 205 Post(s)
Go with the 107 spindle.
JohnDThompson is offline   Reply With Quote
Old 03-30-11, 12:30 PM   #7
ultraman6970
Senior Member
 
Join Date: Dec 2005
Bikes:
Posts: 7,860
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
TO make you feel good... from 108 to 110 are 2 mm difference... 1 mm per side. Doubt that will be a problem or noticeable in the chain line specially using road crankset and track chains.

from 108 to 107 u have 1/2 mm per side, thats nothing.

In numbers looks like too much difference between 108 and 110 but is just nothing, probably a 112 will work fine also (2 mm per side)

Good luck.
ultraman6970 is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 06:49 PM.