French Bottom Bracket
 

Hi All,

I've gotten my hands on an old french bicycle, a "Liberia", probably from the 1970's, and I'm trying to clean it up and get it working properly.

I've taken apart the bottom bracket assembly and am thinking about replacing the whole assembly with a velo-orange french bottom bracket, as the ball bearing retainers are missing bearings and the bearings remaining are deformed and pitted. However, the length of the spindle I removed from the bike is 135mm, and their sizing at velo orange only goes up to 122mm.

So- will a 122mm be compatible, if I fully replace the crank and everything? The only problem I can see would be the problem of setting the chain correctly... but I am not sure. Otherwise, I think I'd have to do some searching for replacement ball bearing retainers to swap out the old pitted ones.

Thanks for any help! Any wisdom is appreciated.

Bottom brackets are the place you want to throw out the old bearings and retainer cages. Replace them with new, 1/4" grade 25 steel bearing balls (11 per side) and fresh grease after throughly cleaning and drying the spindle and cups. Don't bother removing the fixed (drive-side) cup.

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135mm is the original Cottered crank correct? Cottered crank spindles go all the way through the crank arm.

122mm is for cotterless. Should work fine on your bike.

Yes, exactly- the 135mm spindle is for the old style cottered cranks. I am leaning towards getting the 122 mm, as it would have a more modern taper and crank attachment, giving more options for a new crank, pedals, etc.

I guess the only thing I have to figure now is how to get the fixed cup on the right hand side off... haven't been too successful in doing so, it's really stuck on there!

Make sure you're turning it in the "right" direction.

J

French are "standard" threads, rightie tighty, leftie loosy.

You sure? Sheldon says rightie loosey on right fixed cup. That's the way I learned it.

Anyway, my use of the word was a pun. I was just reminding him that French threading is
NOT standard and one unfamiliar with the "extinct" BB needs to be mindful of that.

If I'm wrong I'm willing to learn.

J

Are you trying to save weight?

You'll be going to considerable expense to replace the original components with a VO bb and alloy cranks, as compared to (22) 1/4" ball bearings and two new cotters.
Your original pedals may be French threaded too. (If they are marked D-G instead of R-L, you can bet they are.)

Look again. Sheldon reminds us that French BBs are right-hand, i.e., rightie-tighty. And my old Jeunet does have a right-threaded fixed cup, which did unscrew once in 35 years.

As a previous poster said, you shouldn't need to remove the fixed cup unless it is pitted. (Usually the spindle and the balls wear out long before the cups do.) If your new spindle won't fit through the hole in the cup, then yes, of course you will have to replace the cup. (Been so long since I've seen a cottered crank spindle, I can't remember for the life of me if they are the same diameter.) I would replace just the balls (throw out the cages) and spindle and leave both cups alone if I possibly could.

French bottom brackets are right handed on both sides... Harris is once again selling conventional cup and cone bb sets in a French thread for $19.95 and several Asian suppliers are now offering them quite cheaply.

If you want to lighten the bike and have a little more room to play with chain rings then this is the way to go but if not, old cottered cranks can be quite nice although finding good quality cotters is essential.

Frozen cups in any particular case aside, here's a link to what Sheldon says. I still don't see my error in understanding.

http://www.sheldonbrown.com/bbsize.html#threading

Quoting an excerpt "...prone to problems due to right (right-side, not right-threaded: my words) threaded fixed cup, which tends to unscrew itself in use."

How can a cup "unscrew" itself except in the direction of the rotation of the crank arm? Forward, to the right. That means it turns left to tighten, not "righty tighty".

Still, the original point to my pun is still being missed. It wasn't to argue the technical details on this or any particular case, it was to simply point out the obsolete and faulty nature of the old French BB. It simply is without question "non-standard" and requires a focus that the standard, contemporary threaded BB necessarily doesn't.

By the way, how can one tell if a cup is pitted without removing it? To each his own but rebuilding a BB without inspecting all parts is unacceptable to me. Leaving an unexamined cup in place unless it absolutely frozen beyond removal is a shortcut I'd never take.

J

P.S. I'm moving on.

The fixed cup is on the right side. You're right, the spindle doesn't touch the cup. The balls do and they are going the opposite direction, which tends to loosen the fixed cup. The problem is real and not overblown.

Oops,
My mistake Grand Bois. You're right. Brain fade. That post was so off I've deleted it! What was I thinking? Too early, I guess. Anyway, my fixed cup has never loosened though, but I can only speak from personal experience.

Right, thanks, I'll try replacing the ball bearings first to see if that works.. it will by far be a cheaper fix. If not I'll keep on trying to unscrew this fixed cup.

My one question is: how should I place the ball bearings in the BB without having them in retainers? I'm trying to think of ways but it would seem as though they would be hopping around the BB without being held in some kind of placement. How should I go about this? Thoughts?

I risked everything and lost everything for a French bottom bracket ... :(

I lay the bike on its right side with the fixed cup in place and spread grease in the cup with my finger through the hole in the cup and then feed the 11 1/4" bearings one at a time through the hole. The grease holds them in place. Inserting the spindle locks them in. Fill the adjustable cup with grease and bearings, stand the frame up and carefully screw it in over the spindle. Using a plastic sleeve makes in easier because it holds the bearings in place while you work.

I throw away all retainers because I want my expensive French parts to last forever.

Nah, completely standard for the French!

Well, I learned a lesson from that, too, Grand Bois. Thanks for setting me straight.

I'll leave my faulty post as an embarrassing reminder to be more careful.

Cheers to all.

J

Still quibbling? ;-)

J

Nah, just depends whose "standard" you're following: your's or the other guy's...

Yup. completely standard for the French to be bassackwards to the real world, from what I understand the Italian ones are also right hand threaded on both sides..... It makes things interesting if you go to a bike shop with a younger mechanic, because you don't have the tool, who then strips out the threads because they don't realise that the thread directions differ.....

You're right that the spindle doesn't touch the cup. But the bearings "going the opposite direction" isn't why the cup can unscrew. In fact, there is little or no friction between spindle, bearings, and cup. The bearings do rotate the opposite direction from the spindle but that is because the are rolling around the inside of the cup in the same direction as the spindle turns. Viewed from the drive side, the spindle turns clockwise and balls roll in a clockwise circle.

The reason the cup can be unscrewed is because it is an inside circle. The image shown here illustrates the behavior. If there is any deformation in the shell it will elongate the shell to make it slightly bigger than the cup which has no reason to elongate. Even if stress does not deform the shell, the threads of the cup are necessarily slightly smaller than those of the shell. The cup then rolls around the inside of the shell. Since it is a smaller circle effectively than the shell it takes more than one revolution to roll one loop around the shell. By the time it gets back around to the starting point it will have turned some small amount.
http://users.rcn.com/jimmuller/pics/rotation.gif
It is indeed a real problem. The solution is to make sure the fixed cup is very tightly torqued. Use of a locking material such as Locktight might be useful too. "They" say you should never removed the fixed cup, simply because getting it back tight enough isn't easy.

It's called mechanical precession.

Wow Jim,
That's impressive. But, we're talking the adjustable cup here, right? Since it's the one on the LEFT side of the BB shell ...right?

Hey Jim, thanks for the explanation. I think I finally understand the problem, bearing friction never made intuitive sense but this does.