Hey guys, I need help on a cotter pin for Magistroni crank. I picked up an old sun beat Olmo Special to use as a wall hanger but one of the pins is toast, the crank arm was off and the nut side was mushroomed. The guy I bought from gave me a couple he had as he planned to restore, but they are short. Bike is 61-64' range if that matters.

They appear 9.0 wide. Can someone confirm that size and which ones to get? I see them on Ebay and they look short too.

Thanks!

Italian nearly always take the 9.0mm o.d. size with a medium cut.

have never seen any listing for wedgebolts where the length was discussed. have worked on a great many Magistronis and never encountered any wedgebolt oddities.

wrt your Olmo arrival don't forget to send the serial to the Olmo registry of Peter Breuggeman:

Olmo Serial Number Registry

many readers would enjoy seeing pictures of your bike.

forgot to mention that the forum had a recent thread on an Olmo Special you might like to see if you have not been there already -

https://www.bikeforums.net/classic-vi...-old-olmo.html

Thanks Juvela, so 9mm it is. I had contacted Peter and have been working with him as this bike had a Rondine decal, but was not swallow lug. Looks like they had a QC issue on this one! :-) I may do a thread once I get further along and decide what to do with it.

Here a is the pic of the pins. If you or anyone has a source let me know, or post a link. I don't want to go though the wait and get the wrong one again.

[MENTION=417491]Bikerider007[/MENTION], how does the length of the shorter cotter pin compare with the length of the hole in the crank, through which it's supposed to fit? The cotter has to be a little longer, like maybe 6 mm (1 mm for a washer, 5 mm for a nut), and a couple mm longer than that would be okay too (so a little bit sticks out at the other end). Is your cotter --the one on the right, the "too short" one-- shorter than that?

If the problem is that it doesn't fit into the crank far enough for the threads to come out the other end, you need to file the taper. Of course you should file the taper only when necessary*


*But as Fausto Coppi said, it was always necessary.

I gave it a go just now to double check and the pin pretty much disappears, I can almost push it through by hand and then the threads stick so far out that nut won't tighten down or it would take several washers. The other pin diameter appears the same.

Oh, I get it... sorry, I had not considered that. What you need is not a longer cotter, but one with a different taper. I don't know how you're going to find that, though. Therefore:

I would cut a shim the size of the taper on the cotter. Steel from a coffee can might be thick enough; or you might need two or three layers, I don't know. Make sure it's smooth and flat and fits perfectly in the flat spot between the cotter and the spindle., then proceed as normal.

Yes, this is a cheesy workaround, but as long as the cotter is inserted with enough pressure, it should be okay. Especially if you don't expect to ride the bike a great deal. I'd carry the cotter tool with me when going on long rides.

No worries, I have not taken a cotter crank apart since I was about 16 so I am not sure of anything. I do see the taper you mentioned and will compare that to a search vs size. I may also measure and email some of the ebay sellers and ask for sizes. If not I shall employ the suggested jury rig.

Thank you for this photo Bikerider007.

The item on the right in the image is a 9.0mm with a heavy cut as is used on Peugeot bicycles, and almost nowhere else. These are famous (infamous!) for being difficult to remove due to their large contact area.

The fellow on the left is very typical of a generic 9.0mm with a medium cut as would be found on bicycles of French and Italian manufacture.

Perfect! I will search that route. He must have just ordered the first one he came across.