iab

This may be a question for the mechanics but the bikes are old. I want to mix and match my bottom bracket. The shell and cups will be Italian, 70 mm and I have an axle for the cups. A also bought a great Stronglight single chainring cottered crank with a Stronglight axle.

My ideal set-up would be the cranks on the Stronglight axle with the Italian cups because the chainline spacing for the Stronglight axle is for a single chainring. The problem with that is the race spacing on the axle is French, for 68 mm, while the shell would be Italian at 70 mm. Can the the adjustable cup accomodate the 2 mm difference?

I do have an Italian axle to go with the cups. The problem with that axle is the cranks don't fit as well, good enogh though, and that axle is spaced for a double chainring. The chain line wouldn't be as good. That said, this will be for a fixie and no gears will be changed. Unless someone has one to offer, tracking down an Italian cottered axle for a single chainring will probably be a pain in the a$$.

Any opinions?

coelcanth

probably it will just be a trial and error process.
it might work out ok..
since you have all the parts handy, you can compare the distance between bearing surfaces on the two spindles and also the cup thickness to see if you have a shot before putting everything together.
your chainline still might change a bit since the spindle was designed with different cups in mind

iab

I did a dry fit without the bearings, they are in the mail, and it seems it may work. There is good clearance between the chainring and the frame. Any other interference issues I should be looking for?

unworthy1

The issue I see is that the fixed side is fixed (no sh-t!) and so the 2mm difference in spindle width will come all off the adjustable side, if the inboard spacing of both spindles are identical, the Stronglight will move the left crankarm all 2mm inboard. If that doesn't affect your chainline, then "no worries". Then the deal will be with the adjustable cup: when it's screwed 2mm further into the BB shell is there enough thread left for a lockring? Again, if so then you are golden.Last tiny concern might be the contour difference between the bearing profile of the cups versus the spindle, but probably no big deal and if you use loose bearings instead of caged I'd predict no issues at all there.

top506

I ran a 68mm spindle for years in the 70mm BB of my beater Atala. Never did get a good chainline, but I didn't lose the adjustable cup either (locktite )
But I did eventually find a proper 70mm BB.

cyclotoine

Depends on your inner flange measurement. Campy NR is 51mm and Record is 56mm, keep this in mind. check your stronglight spindle, if the distance between the bearing flanges is the same as the italian BB you have then it will work fine, if it is any smaller you will run into troble. Check the wall thickness of your cups, if you have thinner cups like that of record a solution could be to use Nuovo record cups instead. as they move the bearing in 2.5mm.

Edit, thinking about this you will have to make sure you can tolerate loosing 2.5mm of axle, but old cottered BBs spindles are pretty long aren't they?

iab

How thick is a thick cup and how this is a thin cup? (Pardon my ignorance )

cyclotoine

Sorry I don't know exactly but I think thin cups are about 3 mm and thick more like 5-6mm?? not sure, best to measure your inner spindle flange width. You can ID campy thick cups because they have riffling to move contaminants outboard.

coelcanth

campy thin cups are about 2mm and the thick ones are almost 6mm because of their dirt-repelling rifling...
but since you are using older cottered bb parts they will probably be beefier than the lightweight campy thin cups but not as huge as the rifled cups..

unworthy1 is right about the fixed cup which is why i mentioned chainline, but it is in fact possible to adjust things a littel bit with thin washers

cyclotoine

So if campy thick cups are at least 1mm thicker than the original stronglight cups they should work. The problem as I see it would be that you would not have enough thread for the lockring, unless your italian cups were thicker than the original stronglights.

due ruote 

Another option, if the Italian spindle is asymmetrical, is to flip it 'round so that you have the shorter end on the fixed cup side. This will often give you a better chainline on a FG conversion. Then you don't have to wonder if you have compatibility issues between the cups/bearings/spindle, although I agree with the previous post that you probably won't anyway.

evwxxx

You can also put a spacer ring behind the cup on the fixed side. I just got some the other day. They are basically the same as those used to go behind the freewheel cluster, but they come in various sizes (.5mm, 1mm, 1.5mm, etc).

due ruote 

If I understand the original dilemma, the goal is to move the chainline in, rather than out, as will happen if you insert the spacer.

coelcanth

that's usually true, although with italian parts i guess you could install either cup on any side of the shell..

i just checked out three of my cottered spindles and i can see no rhyme or reason to their dimensions..
they are very weird ! the only thing that seems similar is the non-drive side length