Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

What 73mm bottom bracket for single speed mountain bike?

Notices
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.

What 73mm bottom bracket for single speed mountain bike?

Old 12-06-18, 09:42 AM
  #1  
bark_eater 
Senior Member
Thread Starter
 
Join Date: Sep 2017
Location: Eastern Shore, MD
Posts: 1,432

Bikes: Road ready: 1993 Koga Miyata City Liner Touring Hybrid, 1989 Centurion Sport DLX, "I Blame GP" Bridgestone CB-1. Projects: Yea, I got a problem....

Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 485 Post(s)
Liked 225 Times in 163 Posts
What 73mm bottom bracket for single speed mountain bike?

I'm putting together a winter single speed from a beat up 90's vintage Diamond Back Ascent. The bottom bracket is toast and I would like to replace it with a cartridge BB. It looks like the bike had a 73mm shell and 129mm spindle. The spindle is marked
"7EL Boron J-2" I did not have any luck finding a direct replacement. Could I use a 73x122mm cartridge BB since I'm going to be running converting a triple crank to a single chainring? Thanks, Woody
bark_eater is offline  
Old 12-06-18, 09:52 AM
  #2  
Andrew R Stewart 
Senior Member
 
Andrew R Stewart's Avatar
 
Join Date: Feb 2012
Location: Rochester, NY
Posts: 15,169

Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Raleigh Pro, Trek Cycle Cross, Mongoose tomac ATB, GT Bravado ATB, JCP Folder

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3011 Post(s)
Liked 1,335 Times in 934 Posts
Some of this depends on what rear cog arrangement you choose to do. So a common cassette hub has a lot of possible cog to centerline (chain line) possibilities. A single cog specific hub has only one cog to center option. (Well, maybe two if the cog is dished and can be flipped).

Also the chain is at play. A 1/8" wide chain typically is far less happy with cog/ring misalignment then a 3/32" chain is.

Do you know what the rear cog's center to cog dimension is yet? Have you measured what a ring to center dimension is with the current BB? (Note that here there are two placement options). Andy
__________________
AndrewRStewart
Andrew R Stewart is offline  
Old 12-06-18, 10:03 AM
  #3  
bark_eater 
Senior Member
Thread Starter
 
Join Date: Sep 2017
Location: Eastern Shore, MD
Posts: 1,432

Bikes: Road ready: 1993 Koga Miyata City Liner Touring Hybrid, 1989 Centurion Sport DLX, "I Blame GP" Bridgestone CB-1. Projects: Yea, I got a problem....

Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 485 Post(s)
Liked 225 Times in 163 Posts
I have a single speed conversion kit with cassette spacers so i should be able to get a good chain line. I'm reading this as a 7mm shorter spindle will move the crank 3.5mm closer to the shell and If I move a 36-34 tooth chainring to the outside position It will have more stay clearance than its original position. I think...
bark_eater is offline  
Old 12-06-18, 10:16 AM
  #4  
fietsbob
Banned
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 43,599

Bikes: 8

Mentioned: 197 Post(s)
Tagged: 0 Thread(s)
Quoted: 7607 Post(s)
Liked 1,321 Times in 831 Posts
And it depends on the crankset, if you need a remote guess
as to what square taper spindle length you need to order.

Generally.. middle ring of triple is centered like a single chainring would be..

take off the inner and outer chainring...
fietsbob is offline  
Old 12-06-18, 10:36 AM
  #5  
bark_eater 
Senior Member
Thread Starter
 
Join Date: Sep 2017
Location: Eastern Shore, MD
Posts: 1,432

Bikes: Road ready: 1993 Koga Miyata City Liner Touring Hybrid, 1989 Centurion Sport DLX, "I Blame GP" Bridgestone CB-1. Projects: Yea, I got a problem....

Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 485 Post(s)
Liked 225 Times in 163 Posts
Cranks being mentioned, I dug into the parts pile and compared the original 175mm Exage 400LX with the ratty 180mm Takagi Tourney XT cranks I was going to use and there Is about a very much approximated 10mm difference in "Q" per crank, so 20mm total. They will have to wait for another project.
bark_eater is offline  
Old 12-06-18, 10:56 AM
  #6  
fietsbob
Banned
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 43,599

Bikes: 8

Mentioned: 197 Post(s)
Tagged: 0 Thread(s)
Quoted: 7607 Post(s)
Liked 1,321 Times in 831 Posts
its trial and error time..
what is the axle it came with to use as a triple?
measure , math... add/subtract from there.


maybe someone has those exact parts , and done what you want
for an easy answer..

not me..
fietsbob is offline  
Old 12-10-18, 10:00 AM
  #7  
TireLever-07
Senior Member
 
Join Date: Sep 2005
Location: Malden, MA.
Posts: 402

Bikes: 2009 Masi, 2014 Specialized Crossroads 1975 Schwinn Unicycle

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 11 Post(s)
Likes: 0
Liked 2 Times in 2 Posts
Hi, Watch your clearance on the right chain stay seat stay area, Bottom bracket shell area. A couple weeks ago in a local bikeshop I didn't know how the chain ring & the crank arms, etc have changed these days. If you find one crankset and find some "cheap" chainrings that fit. Try to find a bike co-op. They let me ramble thru their parts barrels. Since the're no discount chain sporting goods stores left here. We have a Bike Not Bombs branch in the City. I haven't had reason to go in there. If you're in a college or urban area. You could bring a tape measure & a straight edge & inspect a few dozen locked up bikes for free. Take Care ,,,cheers
TireLever-07 is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
kimjmoon
Singlespeed & Fixed Gear
7
01-31-13 07:52 AM
chagzuki
Folding Bikes
14
10-10-10 05:26 AM
polobreaka
Singlespeed & Fixed Gear
25
09-06-10 01:16 PM
ted standard
Bicycle Mechanics
16
05-04-10 08:31 PM

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


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.