Coop113

bikemig 

Lucky you not to have a french crank (stronglight or TA); they're beautiful cranks but they need special crank pullers. This one will not. The harder question--and a motobecane expert might be able to help--is the threading on your bottom bracket which may well be French or Swiss threaded (both metric but the fixed cup is right threaded for French, left for Swiss). Finding replacement parts is doable. IRD for example makes french and swiss conversion cups. Velo orange has french threaqed BBs. You can even find french threaded cups on Amazon.

I wouldn't sweat the JIS/ISO thing too much. There are plenty of threads here arguing back and forth on this. This is the best discussion I've seen of the JIS/ISO spindle differences:

https://janheine.wordpress.com/2013/...s-demystified/

The bottom line is that there is some interchangeability between the 2 standards but in any case that does not matter because you have a Japanese crank which will be JIS and so will an IRD sealed unit if you go that route with your bike.

Nice bike btw. I used to own a super mirage and I took it on a long tour. It is a fine machine.

Coop113

bikemig 

I'd do the C&V thing and keep it cheap and rideable. Open up the BB and take a look. It is unlikely that the cups are shot even if the spindle is. You can find a replacement spindle if need be.

Salamandrine 

First of all a standard crank remover is all you need.

You do not need to remove the fixed cup to do a simple overhaul. I recommend against it. Inspect it for pits with a flashlight. If it's trashed, then inquire here again for the next move.

To overhaul: Pull the adjustable cup, pull the spindle and bearing. Clean and regrease. Replace adjustable cup, reinstall crankarms, adjust bearings, done.

When that bike was new there was no such thing as JIS or ISO taper. Don't worry about it.

Coop113

bikemig 

My guess is that this is more of a certainty than a possibility when it comes to the pedals.

Coop113

Salamandrine 

1. It isn't necessary for a repack. It's called a fixed cup for a reason.
2. You are unlikely to have the special BB tool for putting in back on with sufficient torque.

randyjawa 

Removing a fixed cup can be a problem but I usually manage to get them free. This is how I work on bottom brackets and this is the tool I use to help me remove stubborn fixed cups...

clubman 

What's not being said directly is that the ISO/Brit fixed cup is reverse thread so it needs to be buttoned down extremely tight to prevent it from loosening up, as it wants to do as you pedal. Hence Salamandrine's advice. Don't remove it, it creates extra fussy work.

hokiefyd 

I think this is backwards, right? ISO/British/Swiss fixed cups have left hand threads, which prevent the natural tendency to loosen as you pedal. It's the French and Italian fixed cups that have conventional right hand threads, which do tend to want to back out as you pedal. French and Italian fixed cups need to be threaded extremely tight (or use alternative means, like a thread locker) to prevent loosening. ISO/British/Swiss cups aren't nearly as sensitive to installation torque, at least in my own experience.

clubman 

ISO/Brit/Swiss = Reverse thread = left thread. Agreed.

I've never really understood 'precession'. Apparently the force of the rotating spindle causes the cups to move in the opposite direction of that rotation, against what I think would be the case. The threads want to walk out of the shell.

Edit: Here's a small quote from Sheldons pages and J Brandt, "Precession of right-side BB cups is less obvious because the rotating load is only partial. The largest load being chain tension, that together with the moderately large downward force on the right crank and the smaller upward force from pushing down on the left crank, make 3/4 of a fully rotating load. For this reason, some right BB cups have used right hand threads and some with left hand threads have loosened. The left BB cup, with no significant rotating load has little tendency to turn."

He's seems to suggest the left thread fixed cup does loosen.

Anyone else? I'm no engineer.

hokiefyd 

I'm not sure I follow Brandt's logic, that the same force mechanism, that of a clockwise rotating DS crank arm, could loosen cups with different-handed threading. Precession would work to loosen a right-handed threaded DS cup, but it couldn't loosen a left-handed threaded DS cup. I think his sentence is poorly-constructed, and may have been the subject of a cut-and-paste or other typographical error over the years.

"For this reason, some right BB cups have used right hand threads and some with left hand threads have loosened."

Is he saying that cups with either thread have loosened on their own? Again, I'm not sure I follow that logic. "For this reason, some right BB cups have used right hand threads and have loosened." That makes sense. But he or someone has inserted [and some with left hand threads] with goes against the premise of the sentence, and of the rest of the paragraph.

Related thread, with Sheldon's contribution: Bottom Bracket...Left hand thread

hokiefyd 

Anecdote: I rode my late '60s Peugeot mixte to the park two days ago with my daughter. Halfway home (with about 10 miles total on the bike since I assembled the bottom bracket with its new square taper spindle and cotterless cranks), I started feeling a clicking in my pedaling action. It eventually got worse and I stopped to check it out, and the DS bottom bracket cup had indeed unscrewed at least a full turn. I rode it carefully home, about 2 miles further, and it proceeded to slowly get looser. This being my first French-made bike, I tightened the bottom bracket cups like I normally do on ISO/Brit frames, which isn't terribly tight. I never really thought that "precession" thing was real until I experienced it a few days ago.

I went about to fix that yesterday, and really leaned on that DS cup to tighten it. I haven't ridden the bike since, so I guess only time will tell if "Really Tight" is "Tight Enough". I may have to resort to other measures, like thread locker, or a threadless bottom bracket insert.

Salamandrine 

Yeah, not the clearest language. He's basically saying that even the LH threads on BSC or Swiss threads can also loosen up. Indeed, they can. IME.

Again, unless there's some compelling reason to remove it, IMHO, it's best to leave the fixed cup fixed when doing a normal repack.

hokiefyd 

Re-reading the entire post from Brandt, I think he's conjoining two different concepts. I think he's saying that mechanical fretting can cause a left-handed DS cup to loosen, and precession can cause a right-handed DS cup to loosen. He talks about fretting both before and after the sentence in question, and that makes sense to me. Fretting is apparently the physical contact (and deformation) between two surfaces, causing the driven one (the BB cup in this case) to move. With a left-handed DS cup, that action of a forward-rotating crank arm would work to loosen the cup. I've never experienced an auto-loosening ISO/Brit BB cup, but I'll never argue with anyone who says it's happened to them before.

I'll subscribe to that. I removed the DS cup on my Peugeot to clean the 49 year old grease out of it and to test-fit various 68mm square taper spindles I have on hand. I might wish I had just left it alone now, especially if I can't keep it in the frame when I pedal!

desconhecido 

Looked at from the right side, the crank and the BB spindle rotate clockwise. The bearing balls in the BB will, therefore, rotatate, or tend to rotate, counterclockwise about their horixontal axes (assuming an upright bicycle). The force/torque that a CCW rotating bearing ball will exert on the fixed cup, appears to me to be CCW. The same analysis leads me to believe that right side pedals should be rht and left, lht.

Precession has to do with gravity, the earth's gravitational field, and if there are precession forces resulting from pedaling, they need to be countered by forces on the handlebars, not be selecting rht or lht on the BB. Precession forces act normal (90 degrees) to the axis of rotation, not coaxially with the rotation.

I'm not saying that no left-hand thread right side BB cup ever loosened. What I am saying is that if everything is functioning properly, it shouldn't.

Dfrost 

Andy_K 

I've since repeated this trick with my other Motobecane and my Stella. You'd think I would have learned to use some blue Loctite after the first one, but you'd be wrong. I'm a slow learner. With the Stella, at least, I was lucky enough to have it happen less than a mile from home, and with the second Motobecane I was able to hand thread it in far enough to limp home. I've now got a saddle bag packed with the tools I need to fix this problem on the road.

In any event, I'd be surprised if the OP's bottom bracket isn't at least Swiss threaded, maybe even English. My first experience with hand-wringing over this problem was with a 1977 Gitane Gypsy Sport, and that one turned out to be English. With the Motobecane, I'd guess Swiss. I think my Gitane was actually made in Japan. I'm not aware of Motobecane having done that with any of their bikes in the 70's. Of course, if the OP doesn't have to remove the fixed cup he won't even need to know or care whether it's Swiss or French.

Lascauxcaveman 

Man, I don't personally use Locktite on anything, but if I was you, I would. Thatsa lotta loose-goosey BBs!

Andy_K 

Well, supposedly the blue Loctite (242) can be disassembled with normal tools. I haven't had to test that theory yet. The Grand Record, which @Dfrost referenced failing on our Banks-Vernonia trip, is actually still relying on good old-fashioned torque right now. You may recall my story from that day about having a little trouble convincing the shop keeper in Banks to believe in the existence of French threading. There was no way I was going to suggest that he put Loctite on my bike. I've put a couple of hundred miles on it since that day and it's still holding but I don't entirely trust it. It'll get Loctite the next time I have a reason to take out the bottom bracket.

Of course, @gugie tells me he can keep the cups from unthreading with his torch. No word on how I'd do maintenance after that though.

Lascauxcaveman 

When you're surgeon, every job looks like it needs some cutting

Ghrumpy

Sure. To be more precise it's epicyclic fretting precession we're talking about, and that's the only kind of precession that pertains to bicycles in a meaningful way.

That's a big if.

And what you're saying is tautological: No "properly" functioning fastener should ever loosen. LH threads on pedals and BBs are concessions to reality, where bearings are not always properly adjusted, tolerances are not always properly machined, etc.