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 02-10-08, 09:11 AM   #1
supton
Cries on hills
Thread Starter
 
supton's Avatar
 
Join Date: Jun 2007
Location: Central NH
Bikes: 2007 Trek Pilot 1.2, 1995 Gary Fisher Avantage, 1985 Panasonic Sport 1000, 1969 Raleigh Sprite 5
Posts: 877
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
BB Rethreading

I keeping thinking about older Raleighs, and their 26tpi BB being an issue when converting to modern cranks. Supposedly they can be retapped to 24tpi, but some worry about the threads being too weak. Why is that? I can understand that the threads may be weak; but is that for fear of the BB stripping out and ruining the frame; or because of fear of some sort of crash from the BB getting loose?
supton is offline   Reply With Quote
Old 02-10-08, 09:27 AM   #2
HillRider 
Senior Member
 
Join Date: Aug 2005
Location: Pittsburgh, PA
Bikes: '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
Posts: 28,776
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 36 Post(s)
The problem is the Raleigh threads are exactly the same diameter as 24 tpi English threads so you will weaken the threads if you change the pitch.

A crash from a loose bb probably isn't an issue unless you ignore the symptoms for way too long. It isn't going to catastrophically pop out. Maybe retaping and using a lot of Loctite on the new bb is feasible.

One way to salvage a damaged English (or Raleigh) bottom bracket is to have it reamed and retapped with Italian threads and use spacers to widen the 68 mm shell to accept 70 mm Italian bb. The frame has to be valuable, at least to you, to bother with this.
HillRider is offline   Reply With Quote
Old 02-10-08, 09:41 AM   #3
supton
Cries on hills
Thread Starter
 
supton's Avatar
 
Join Date: Jun 2007
Location: Central NH
Bikes: 2007 Trek Pilot 1.2, 1995 Gary Fisher Avantage, 1985 Panasonic Sport 1000, 1969 Raleigh Sprite 5
Posts: 877
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I'm thinking of, get a cool old Raleigh and then upgrade with new bits as I feel like. Shedding weight would be nice, but I'm more concerned with the pains of initially tearing it apart to relube parts, then having to deal with cottered cranks--I'd rather tear it apart and rebuild "right" up front. I'm just guessing that a 30 year old BB ought to be torn apart right off for regreasing.

I'm guessing a bit of Loctite when I put in the BB would be a good idea--not the "never remove again" level but the version that just applies a bit more force than nothing. A good modern sealed BB shouldn't need touching for years.
supton is offline   Reply With Quote
Old 02-10-08, 10:00 AM   #4
HillRider 
Senior Member
 
Join Date: Aug 2005
Location: Pittsburgh, PA
Bikes: '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
Posts: 28,776
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 36 Post(s)
Years ago, I replace the OEM Stronglight cottered crank in a friends '72 Super Course with a "modern" square taper Shimano crank and ran into the same threading problem. I used just the spindle from a proper length cup-and cone bb and retained the original Raleigh cups which were in good condition. You might try this first and rethread the frame only if the stock cups are in bad shape.
HillRider is offline   Reply With Quote
Old 02-10-08, 10:07 AM   #5
supton
Cries on hills
Thread Starter
 
supton's Avatar
 
Join Date: Jun 2007
Location: Central NH
Bikes: 2007 Trek Pilot 1.2, 1995 Gary Fisher Avantage, 1985 Panasonic Sport 1000, 1969 Raleigh Sprite 5
Posts: 877
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
That is true too. I am looking at a Twenty for fun, as I spend one weekend/month away from home. The Twenty supposedly needs a really long spindle though, but it is another option. I don't have a junkbox of parts (yet).
supton 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 07:13 PM.