Go Back  Bike Forums > Bike Forums > Classic & Vintage
Reload this Page >

What BB for older motobecane?

Notices
Classic & Vintage This forum is to discuss the many aspects of classic and vintage bicycles, including musclebikes, lightweights, middleweights, hi-wheelers, bone-shakers, safety bikes and much more.

What BB for older motobecane?

Old 09-23-07, 09:38 AM
  #1  
Senior Member
Thread Starter
 
Join Date: Mar 2007
Location: SF
Posts: 1,572

Bikes: 1972 Paramount Track, 1972 Paramount P13 Road, 1972 Paramount Tandem, 1986 Paramount Road, Merckx MXL, Gunnar Cross Hairs, Samson Illusion NJS, KHS Aero Track, Titus Racer X 29er, Tom Palermo Custom Touring

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 4 Times in 2 Posts
What BB for older motobecane?

I have a friend who stripped a Tourny crank arm on his Motobecane, and has tasked me with replacing the crank arm (which has proved difficult) or the whole crankset. Would it have a 68mm shell, if so what threading? Or if I kept the bottom bracket what taper crank would I need?
anomaly is offline  
Old 09-23-07, 02:01 PM
  #2  
juneeaa memba!
 
Join Date: Oct 2003
Location: boogled up in...Idaho!
Posts: 5,632

Bikes: Crap. The box is not big enough...

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 13 Post(s)
Likes: 0
Liked 3 Times in 3 Posts
What vintage? If 80's it is probably BSC, and probably marked to indicate somewhere on the frame. The Japanese crank is also a strong indicator for BSC. It would almost surely be a 68. If it is newer, then the width can wander. If its an old one, it may be French, as the Japanese built to both standards. Dunno when Tourney was popular.
luker is offline  
Old 09-23-07, 06:31 PM
  #3  
feros ferio
 
John E's Avatar
 
Join Date: Jul 2000
Location: www.ci.encinitas.ca.us
Posts: 21,764

Bikes: 1959 Capo Modell Campagnolo; 1960 Capo Sieger (2); 1962 Carlton Franco Suisse; 1970 Peugeot UO-8; 1982 Bianchi Campione d'Italia; 1988 Schwinn Project KOM-10;

Mentioned: 44 Post(s)
Tagged: 0 Thread(s)
Quoted: 1384 Post(s)
Liked 1,293 Times in 819 Posts
Moto changed from French to Swiss BB threading sometime in the mid-1970s, before Peugeot did, but I believe both companies went to ISO by the mid 1980s. The square crank taper itself is always 2 degrees, but Shimano cut its cranks to a fatter end width than everyone else. Circa 1994 Campagnolo reportedly copied Shimano.
__________________
"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069
John E is offline  
Old 09-23-07, 10:04 PM
  #4  
juneeaa memba!
 
Join Date: Oct 2003
Location: boogled up in...Idaho!
Posts: 5,632

Bikes: Crap. The box is not big enough...

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 13 Post(s)
Likes: 0
Liked 3 Times in 3 Posts
ISO is BSC, I think...the vast majority of the Japanese parts in the world are ISO, but they supported most of the standards to some degree.
luker is offline  
Old 09-23-07, 11:59 PM
  #5  
Senior Member
 
Join Date: Aug 2007
Location: Western North Carolina
Posts: 437
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by luker
ISO is BSC, I think...the vast majority of the Japanese parts in the world are ISO, but they supported most of the standards to some degree.
Can somebody explain the alphabet soup?
digitalbicycle is offline  
Old 09-24-07, 07:09 AM
  #6  
Senior Member
 
nick burns's Avatar
 
Join Date: Oct 2004
Location: Absecon, NJ
Posts: 2,947

Bikes: Puch Luzern, Puch Mistral SLE, Bianchi Pista, Motobecane Grand Touring, Austro-Daimler Ultima, Legnano, Raleigh MountainTour, Cannondale SM600

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Originally Posted by digitalbicycle
Can somebody explain the alphabet soup?
Who better than Sheldon?

https://www.sheldonbrown.com/gloss_ta-o.html
nick burns is offline  
Old 09-24-07, 09:37 AM
  #7  
Senior Member
 
Join Date: Nov 2004
Posts: 23,233
Mentioned: 652 Post(s)
Tagged: 1 Thread(s)
Quoted: 4719 Post(s)
Likes: 0
Liked 3,034 Times in 1,874 Posts
Originally Posted by nick burns
Be aware that there are a couple of places in that article on threading that are misleading. If you go based strictly on the data in the charts, you'll be OK, but the written text that can cause some confusion if you try and relate it to the charts.

There are three common thread systems, not two as Sheldon states. In addition to metric and SAE/American (i.e. uses English units of measurment), there is a hybrid system that combines both English and metric units of measurments. For instance, Italian bottom bracket and freewheel threads are 36mm x 24 TPI. That's a metric nonimal diameter combined with a English thread pitch measurement.

He also states one of the systems as being "metric (ISO)". ISO is not exclusively metric. When the International Standards Organization was chosing the bicycle threads standards, they looked at the technical merits while considering the financial impact. In other words, they wanted the best thread, but not if the majority of the bicycle manufacturers would have to change. Consequently, ISO selected standards from both English and metric systems, depending on the application. For instance, the ISO bottom bracket thread standard, uses an English measurement system, while the ISO axle thread standard is metric based.

Note that an ISO English based system is not the same as English threading. While they are compatible, there are minor differences in the thread profile and sometimes the nominal diameter.

Last edited by T-Mar; 09-24-07 at 09:44 AM.
T-Mar is offline  
Old 09-24-07, 03:58 PM
  #8  
Gone, but not forgotten
 
Sheldon Brown's Avatar
 
Join Date: Jul 2002
Location: Newtonville, Massachusetts
Posts: 2,301

Bikes: See: https://sheldonbrown.org/bicycles

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 24 Post(s)
Likes: 0
Liked 6 Times in 5 Posts
From: https://www.sheldonbrown.com/gloss_ta-o.html#threading :
Threading Systems
For normal, generic nuts and bolts, there are two threading systems in common use, S.A.E. (U.S.Standard) and Metric (I.S.O.). S.A.E. threads are designated by a diameter and a number of threads per inch (TPI). For example, the common 1/4 - 20 means a bolt 1/4 inch in diameter, with 20 threads per inch. Metric bolts are sized by the diameter and the distance between adjacent threads, for example 6 x 1 refers to a bolt 6 mm in diameter with threads 1mm apart. (This is the size used for brake mounting bolts and brake shoe hardware.) Similarly, 5 x .8 means a bolt 5 mm in diameter, with threads .8 mm apart. (This size is used for fender and bottle-cage fittings, shift lever bosses, and most cable anchor bolts.) A third system, known as Whitworth, was used in Britain up until the 1960's when they converted to metric.

Bicycle parts come in even more different thread systems than common nuts and bolts. There are different standards for headsets and bottom brackets for American/BMX/OPC, British, French, Italian, Raleigh and Swiss bicycles.
Originally Posted by T-Mar
Be aware that there are a couple of places in that article on threading that are misleading. If you go based strictly on the data in the charts, you'll be OK, but the written text that can cause some confusion if you try and relate it to the charts.

There are three common thread systems, not two as Sheldon states. In addition to metric and SAE/American (i.e. uses English units of measurment), there is a hybrid system that combines both English and metric units of measurments. For instance, Italian bottom bracket and freewheel threads are 36mm x 24 TPI. That's a metric nonimal diameter combined with a English thread pitch measurement.
The first of the two paragraphs above is referring to "Normal generic nuts and bolts" The Italian thread system is a non-issue for nuts and bolts.

The second paragraph, beginning "Bicycle parts come in even more different thread systems than common nuts and bolts" does mention the Italian (and other oddball) threading as used specifically on bicycle parts, such as bottom brackets, headsets, hubs.

Originally Posted by T-Mar
He also states one of the systems as being "metric (ISO)". ISO is not exclusively metric.
For "Normal generic nuts and bolts" ISO is exclusively metric. That's what that paragraph was talking about.

Originally Posted by T-Mar
When the International Standards Organization was chosing the bicycle threads standards, they looked at the technical merits while considering the financial impact. In other words, they wanted the best thread, but not if the majority of the bicycle manufacturers would have to change. Consequently, ISO selected standards from both English and metric systems, depending on the application. For instance, the ISO bottom bracket thread standard, uses an English measurement system, while the ISO axle thread standard is metric based.

Note that an ISO English based system is not the same as English threading. While they are compatible, there are minor differences in the thread profile and sometimes the nominal diameter.
That's correct.

I have "bolded" the sections of each of those two paragraphs that differentiate what they are addressing. I hope this helps clarify the respective issues discussed in those two paragraphs. If not, and you have any suggestions for improved wording, I'm glad to consider them.

Sheldon "Revision Is Easy On The Web" Brown
Sheldon Brown is offline  
Old 10-22-07, 02:05 PM
  #9  
Senior Member
 
Join Date: Oct 2007
Posts: 97
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
My Moto from the mid-70's has a 68 mm Swiss-threaded BB
Purp is offline  

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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.