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Crank arm attachment bolt snapped
#1
So I thought I'd be a brave lad and investigate a rouge squeak somewhere in the pedals/crankset of a Motobecane Mirage I have. After I realized I didn't have the parts, I began screwing a nut back onto the bolt that i *think* holds the crank arm on. While doing this I over tightened and.. snapped the bolt.

[attachment=1156]

So my bike needs work and I am 'other-side' shade of green in the bike world. Plus, I've heard nightmares about replacing parts on french bikes. Is it worth scouring San Francisco for that one bolt/piece, or do you think it's more worth my time going for a full crank arm or crankset replacement? And, if the latter, what kind of parts am I looking for?

Thanksamuch for any input.
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#2
This is a cotter pin, see them on this page;
http://www.cyclesofyesteryear.com/cycleshop/sparepart.htm
however, your's is almost certainly a continental (Europe) size which is smaller than the Imperial size shown, you will have to search for these, a good (old fashioned) lbs should be able to find them for you.

To remove, simply tap out with a punch on the broken end, it helps to support the crank arm, then measure the dia. of the pin, if this is 3/8" then it's the imperial size, if it's smaller it's the continental size.

When re-installing, make sure the nuts are opposed, or you will end up with the crank arms out of line, it is also sometimes necessary to file the flat on the pin to get full engagment.
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#3
Further info, the dia. of the continental cotter pin is 9mm.(.352")
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#4
The size of the cotter pin will probably 9.5mm in all the ones I have handled even the English 3speeds that was the size, here are some more tips along with trev's http://www.sheldonbrown.com/cotters.html . Have to say that I never seen one break off like this one. Also here is the tool I use to remove them, BUT only get it if you work with bikes that have the cottered cranks .... http://www.bikesmithdesign.com/CotterPress/index.html
Good maintenance to your Bike, can make it like the wheels are, true and smooth!
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#5
(07-13-2010, 11:41 PM)Bill Wrote:  The size of the cotter pin will probably 9.5mm in all the ones I have handled even the English 3speeds that was the size, here are some more tips along with trev's http://www.sheldonbrown.com/cotters.html . Have to say that I never seen one break off like this one. Also here is the tool I use to remove them, BUT only get it if you work with bikes that have the cottered cranks .... http://www.bikesmithdesign.com/CotterPress/index.html

Yes, Bill, bikes originating in the UK will have a cotter pin of 3/8" body dia. which = 9.5mm. but this is a French bike, and everyone I have worked on had a 9mm. cotter pin.
I had a root around in my bits and pieces box and actually have one of these!!
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#6
Ok, trev, I'll admit never had the pleasure of working on a French bike and I'm glad you shared this. The Brittany FreeSpirit I have shown was 9.5mm which is not a English make which is newer then the Armstrong I restored. This is definitely an area I want to do a video on.
Good maintenance to your Bike, can make it like the wheels are, true and smooth!
  Reply


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