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heatherlovine

So I recently decided to switch from my original banged up cottered cranks to cotterless cranks. I know that French threads and components differ so is there anything I should know or have to purchase before I attempt to switch them out?

it's an early 70's grand sport delux BTW

vanhelmont

The simple way will be to replace your bottom bracket with a French thread bottom bracket that has a spindle of the appropriate length and taper for the cranks you use. There seem to be two choices for a new French BB, Phil Wood or Edco, which are cheaper than Phil. Velo Orange carries the Edco bb's and if I hadn't already put the bucks into an old bb from ebay that's what I would buy.

http://www.velo-orange.com/edbobr.html

You can also find old French bb's on ebay, like I did.

The cheap way will be to just replace the spindle, which you should be able to do if you can find a spindle that
a. fits the cups, and
b. fits the cranks.

Sheldon Brown is the oracle for wisdom on both subjects. See

http://sheldonbrown.com/bbsize.html

He gives the spindle lengths for various cranks, and also info about matching or mixing iso and Japanese cranks and spindles. Somewhere, I don't think it's on this page, he comments on replacing French bb spindles, and says with thicker cups a spindle intended for a British thread bb will work, while with thinner cups a spindle from an Italian bb will probably work.

Good luck, and let us know how it comes out.

verktyg

There are several problems reusing the old cups from a cottered bottom bracket.
1. the bottom brackets that European bike manufacturers used on their lower cost bikes were generally very poor quality. The cups and spindles were usually made of case hardened steel rather than through hardened bearing steel like that used in better quality components. The case hardened bearing surfaces could be as little as .005" (0.127mm) thick.

Frequently dirt got into these bottom brackets either through gaps around the BB spindles or from residual junk inside the frame. Once the case hardened surface was damaged the cups and spindles quickly wore out.

2. there is no standard for the width of the bearing surfaces on BB spindles or the thickness of the cups. Sutherland's Handbook for Bicycle Mechanics has a whole chapter on what cups and spindles will interchange.

My suggestion is to decide on what crankset you want and find a BB that will work with it. The easiest might be to get an older TA or Stronglight crankset on eBay and get a BB to go along with it. For the most part, their BBs are interchangeable. Earlier Stronglight double cranks fit on a 118mm wide BB spindle.

Pre 1978 Campy and Campy knockoff cranksets will work with Campy or Sugino 113mm wide spindles which you can find of eBay. Crankset made after the mid 80s usually take narrower spindles than the older cranks. It then becomes a game of trial and error. Putting a Phil BB cartridge in an old bike like a Gitane Gran Sport is like putting silk stockings on a rooster! Rolling Eyes

Some of the earlier Shimano BB cartridges had removable cups on both ends. You can sometimes find these for under $30. You can use them with Phil French cups which you can buy in a set of right & left.

Good luck,

Chas.