Vintage French cotter pin problem

swee'pea99

Legendary Member
I'm having trouble with installing new cotter pins on my daughter's old Le Jeune. The problem is that the new pins seem to go too far through the cranks, so when they're tight enough to do their job, you can't actually secure them in place, because there's no thread left to screw onto.

I did my best with the last one:

1602169219323.png


...but unsurprisingly it's worked its way loose again.

I tried installing a new one:

1602169258908.png


...but as you can see, there's no way I'll get a nut snug against the crank on that - and I haven't even hit it yet! By the time it's properly tight, it'll be another mm through.

These are proper (9mm) continental cotter pins, so I'm thinking they really ought to work. Any thoughts/advice would be much appreciated. Not least because this is the third or fourth time in a couple of years, and it's really doing my head in. :wacko:

Thanks if you can help.
 

figbat

Slippery scientist
Would an English 9.5mm work in there? Is it the original crank and, if so, was the crank French style?
 

Once a Wheeler

Senior Member
Would an English 9.5mm work in there? Is it the original crank and, if so, was the crank French style?
Agree with figbat: give a 9.5mm cotter a try. You may have to file down the flat a bit but it may then prove to be just right. I suspect what may have happened is that the bike was serviced in the UK at some point and the bike shop reamed out the cotter hole to the UK size because they did not have any 9mm pins. Gnutti and other Continental cranks were at one time routinely offered for sale with the option of either the original bore or else reamed to UK standard.
 
OP
swee'pea99

swee'pea99

Legendary Member
Many thanks - that makes excellent sense! I shall get hold of some 9.5s and give it a go.
 
OP
swee'pea99

swee'pea99

Legendary Member
Use a larger washer as a spacer.
That's another great suggestion! And one I will try (tho' I will actually try using more than one washer, rather than trying to track down a particularly thick one). Not least because my British cotter pins arrived and they won't go thru', no way no how. So I'm pretty sure it never has been reamed out to 9.5mm - the basic problem is, really, that it's just worn. Only fractions of a mm, but enough so a 9mm pin is too small, a 9.5mm one too large. I think my last throw of the dice before I throw the damn thing in the canal will be a new 9mm + 2 x washers, then pray.

(Does anyone know, could I replace the cranks with old British ones? Is the axle on an old French bottom bracket the same as on an old British one? I have a horrible feeling that the answer to this is 'Non!', but it can't heurt to ask.)
 

tyred

Legendary Member
Location
Ireland
That's another great suggestion! And one I will try (tho' I will actually try using more than one washer, rather than trying to track down a particularly thick one). Not least because my British cotter pins arrived and they won't go thru', no way no how. So I'm pretty sure it never has been reamed out to 9.5mm - the basic problem is, really, that it's just worn. Only fractions of a mm, but enough so a 9mm pin is too small, a 9.5mm one too large. I think my last throw of the dice before I throw the damn thing in the canal will be a new 9mm + 2 x washers, then pray.

(Does anyone know, could I replace the cranks with old British ones? Is the axle on an old French bottom bracket the same as on an old British one? I have a horrible feeling that the answer to this is 'Non!', but it can't heurt to ask.)
I'd suspect someone rode it for years with loose cotterpins which over time will damage the cranks and the spindle. The larger washer should work though as I've done it on bikes in the passt.

If the machined part of your bottom bracket spindle is wide enough to accept the British 3/8" cotterpin (it probably is but only one way to find out), then I don't see any reason why you couldn't use British cranks.

You could replace the spindle if necessary and keep the existing BB cups (which I assume are French threaded?). I'd measure your existing bottom bracket spindle and try to find a match - something like this (you will see how you need to measure it from the diagram) - https://www.sjscycles.co.uk/bottom-brackets/cottered-bottom-bracket-axle-2c/

A further thing to consider is a change to square taper, either find the correct spindle and keep your existing cups or I think a threadless bottom bracket should fit a French threaded frame.
 
OP
swee'pea99

swee'pea99

Legendary Member
I'd suspect someone rode it for years with loose cotterpins which over time will damage the cranks and the spindle. The larger washer should work though as I've done it on bikes in the passt.

If the machined part of your bottom bracket spindle is wide enough to accept the British 3/8" cotterpin (it probably is but only one way to find out), then I don't see any reason why you couldn't use British cranks.

You could replace the spindle if necessary and keep the existing BB cups (which I assume are French threaded?). I'd measure your existing bottom bracket spindle and try to find a match - something like this (you will see how you need to measure it from the diagram) - https://www.sjscycles.co.uk/bottom-brackets/cottered-bottom-bracket-axle-2c/

A further thing to consider is a change to square taper, either find the correct spindle and keep your existing cups or I think a threadless bottom bracket should fit a French threaded frame.
Thank you, that's really helpful.

Can I ask, when you say 'larger washer', do you mean one that's thicker, or one that's got a bigger hole in the middle (or both)? I'd like to try that first! If that doesn't work, I might move on to new spindle, but the washer seems like the way to go if it's possible.
 

tyred

Legendary Member
Location
Ireland
Thank you, that's really helpful.

Can I ask, when you say 'larger washer', do you mean one that's thicker, or one that's got a bigger hole in the middle (or both)? I'd like to try that first! If that doesn't work, I might move on to new spindle, but the washer seems like the way to go if it's possible.
I mean a washer with an internal diameter big enough to go over the thick part of the cotterpin so that when you tighten the nut, it can pull tight and stay tight and not have a gap between the nut and the crank to allow the cotterpin to come loose.

Basically the washer needs to fit into the gap where the red arrow points and have a large enough internal diameter to allow the cotterpin to pass through it and be thick enough so that the threads do not bottom out. You might need two, you will struggle to find 9mm washers I expect but 3/8" would be perfect and should be easily available.
553218
 
OP
swee'pea99

swee'pea99

Legendary Member
I mean a washer with an internal diameter big enough to go over the thick part of the cotterpin so that when you tighten the nut, it can pull tight and stay tight and not have a gap between the nut and the crank to allow the cotterpin to come loose.

Basically the washer needs to fit into the gap where the red arrow points and have a large enough internal diameter to allow the cotterpin to pass through it and be thick enough so that the threads do not bottom out. You might need two, you will struggle to find 9mm washers I expect but 3/8" would be perfect and should be easily available.
View attachment 553218
That's brilliant, thanks very much. Really appreciate your help.
 

Once a Wheeler

Senior Member
British cotter pins arrived and they won't go thru', no way no how.
I suspect you will have done this but just to be sure you are not missing a trick, have you tried to push the British pins through the hole when the crank was removed from the spindle? If it is too big to even enter the hole when the crank is detached, then it is too big. If it does enter the hole when the crank is detached, then you just have to file down the flat. This is normal procedure. If you do this, make three or four file strokes on the flat surface and try to fit the pin; repeat until the fit is good. Take it in small steps as the difference between a fit and falling through the hole is quite small.
Another, perhaps easier solution: take the crank to a bike shop and get them to ream out the cotter hole to the UK size. This takes about 20 seconds and they should be able to do it while you wait. If you are a regular customer, they might not even charge you. All the best.
 
OP
swee'pea99

swee'pea99

Legendary Member
I suspect you will have done this but just to be sure you are not missing a trick, have you tried to push the British pins through the hole when the crank was removed from the spindle? If it is too big to even enter the hole when the crank is detached, then it is too big. If it does enter the hole when the crank is detached, then you just have to file down the flat. This is normal procedure. If you do this, make three or four file strokes on the flat surface and try to fit the pin; repeat until the fit is good. Take it in small steps as the difference between a fit and falling through the hole is quite small.
Another, perhaps easier solution: take the crank to a bike shop and get them to ream out the cotter hole to the UK size. This takes about 20 seconds and they should be able to do it while you wait. If you are a regular customer, they might not even charge you. All the best.
Again, many thanks. Yes, the pin is definitely too big - the crank's off at the mo, and it's not close to going through. Getting the crank reamed is definitely an option, but I'd probably keep that for 'last resort'. Washers first... when I get a few minutes to play.
 
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